Accuracy – 1) In archaeological predictive models, the ability to correctly predict site presence in a parcel of land (see Precision). Accuracy is a function of the percentage of known sites that are in medium and high probability areas. 2) In spatial data, the ability to represent the true locations of geographic features and attributes of the features.
Aceramic - A term that refers to any site or cultural complex lacking pottery or ceramics. Aceramic sites may be those that pre-date the presence of pottery at around 1000/500 B.C. or ones that represent special activity sites occupied after the introduction of ceramics. In the latter case, the absence of pottery is the result of activities not requiring them (e.g. chipped stone reduction).
Age Ranking. A toggle value ("0" or "1") indicating that the strata are of the age, or not of the age to contain cultural deposits. When multiplied by the depositional or post-depositional environment ranking the product is a landscape suitability ranking.
Alcove Bars. Kehew and Lord (1986) defined this bar landform as being on the inside of a catastrophic flood marginal channel landform, which has cut an arc or crescent into the pre-existing landscape.
Alluvial Fan. A low, outspread, relatively flat to gently sloping mass of loose rock material, shaped like an open fan or a segment of a cone, deposited by a stream (esp. in a semiarid region) at the place where it issues from a valley upon a plain or broad valley, or where a tributary stream is near or at its junction with the main stream, or wherever a constriction in a valley abruptly ceases or the gradient of the stream suddenly decreases; it is steepest near the mouth of the valley where its apex points upstream, and it slopes gently and convexly outward with gradually decreasing gradient.
Alluvium. A general term for clay, silt, sand, gravel, or similar unconsolidated detrital material, deposited during comparatively recent geologic time by a stream or other body of running water, as a sorted or semisorted sediment in the bed of the stream or on its floodplain or delta, as a cone or fan at the base of a mountain slope; esp. such a deposit of fine-grained texture (silt or silty clay) deposited during time of flood.
Archaeological Resource Region - Environmental regions based on surface hydrology of the state of Minnesota, that is, on the lake and stream systems. In this project, Phase 1 and 2 modeling regions were based on nine archaeological resource regions in Minnesota.
Archaic - A time period or cultural tradition present throughout much of North American and dated from about 6000/5000 B.C. to 1000/500 B.C. Archaic peoples relied on a mixed subsistence economy of hunting and foraging.
ARC/INFO - One of the most powerful and widely used GIS packages, developed by Environmental Systems Research Institute (ESRI). It provides the tools for users to digitize, edit, access, visualize, query, analyze, and manipulate both geographic and tabular data for analysis and decision making.
Artifact - Any object modified from its naturally occurring state by human action. Common archaeological artifacts from the prehistoric period include flaked stone, pottery, fire-cracked rock, fractured animal bone, and burned seeds. An artifact can also apply to unmodified objects that have been transported from their natural setting, such as a clamshell located in an upland archaeological site.
Attribute Table - Tabular file containing rows and columns. In GIS, attribute tables are associated with a class of geographic features, such as wells or roads. Each row represents a geographic feature. Each column represents one attribute of a feature, with the same column representing the same attribute in each row.
Bar (coast). A generic term for any of the various elongate offshore ridges, banks, or mounds of sand, gravel, or other unconsolidated material, submerged at times, and built up by the action of waves or currents on the water bottom at a slight distance from the beach.
Bar (streams). A ridgelike accumulation of sand, gravel, or other alluvial material formed in the channel, along the banks, or at the mouth, of a stream where a decrease in velocity induces deposition; e.g., a channel bar or a meander bar.
Beach Ridge. A low, essentially continuous mound of beach or beach-and-dune material (sand, gravel) heaped up by the action of waves and currents on the backshore of a beach beyond the present limit of storm or the reach of ordinary tides, and occurring singly or as one of a series of approximately parallel deposits. The ridges are roughly parallel to the shoreline and represent successive positions of an advancing shoreline.
Bog. (a) Waterlogged, spongy ground, consisting primarily of mosses, containing acidic, decaying vegetation that may develop into peat. (b) The vegetation characteristic of this environment, esp. sphagnum, sedges, and heaths.
Bayesian Information Criterion (BIC)- a calculated value that provides a major criterion of the model's strength. It is based on the model's fit to the data minus a complexity penalty. This calculation was included in a logistic regression function written for the statistical analysis software, S-Plus.
Biophysical Context - Characteristics of parcels of land composed of both biological (e.g., plant community type) and physical (e.g., soil type, distance to water) aspects of the natural environment that provide a setting, or context, against which archaeological site presence and absence can be measured.
Biostratigraphic Interpretation of Plant Macrofossils - The identification of plant seeds, bark, twigs, etc. buried within sediments. This procedure allows a scientist to correlate lithologic units within the river basin, region, and possibly the state.
Buried Horizons - Any of the series of distinctive layers found in the lower, or buried, portions of a vertical cross section of any well-developed soil or stratigraphic sequence. The words ‘buried horizons’ are commonly used to describe a well-developed soil or stratum that has subsequently been buried by more recent sediment.
By-Chance Locational Model - The "pure chance" probability that a land parcel does or does not contain archaeological resources. By-chance models are often calculated by determining the relative frequency of the presence or absence of resources in a random sample of surveyed land parcels. Since all land parcels are considered equal in this approach, predictive models that identify associations between resource presence and particular variable features of these parcels should provide higher predictive probabilities than by-chance models. By-chance locational models provide a baseline against which the performance of other predictive models can be judged.
Cell Size - In raster processing, data is represented spatially on a matrix of grid cells, called pixels, which are assigned values for image characteristics or attributes. Cell Size refers to the actual size of the grid cells or pixels. For instance, the cell size of a raster data set might be 30 meters or it could be 50 meters. Smaller grid cell sizes have a higher resolution than larger grid cells. However, a matrix of smaller cells will require more computer storage capacity and processing time.
Chi-Square - Rather than measuring the value of each of a set of items, a calculated value of chi-square compares the frequencies of various kinds (or categories) of items in a random sample to the frequencies that are expected if the population frequencies are as hypothesized by the investigator. Chi-square is often used to assess the "goodness of fit" between an obtained set of frequencies in a random sample and what is expected under a given statistical hypothesis. For example, chi-square can be used to determine if there is reason to reject the statistical hypothesis that the frequencies in a random sample are as expected when the items are from a normal distribution.
Classification - A method of generalization. In the process of classification, an attempt is made to group data into classes according to some common characteristics, thereby reducing the number of data elements. Classification tends to be based upon the attributes or characteristics of data rather than their geometry.
Colluvium. A general term applied to any unconsolidated sediment deposited by rainwash, sheetwash, slope failure, or slow continuous downslope creep, usually collecting at the base of slopes or hillsides.
Continuous Logistic Transformation Scale - A statistical scale along which various measures of association of "archaeological resource present" and different combinations of environmental variables fall. Decision rules are points along this scale above which there is a specifiable probability that an archaeological resource will be present. A goal of the project, for instance, is to determine the point above which the presence of an archaeological resource is highly likely for various parts of the state.
Continuous Variable - A variable is said to be continuous if the values / observations belonging to it may take on any value within a finite or infinite interval. You can count, order and measure continuous data.
Compaction Ridge. A ridge created by differential compaction ("dewatering") of underlying sediments. The ridge is often linear in shape because of fluvial sands and gravels not compacting as much relative to the surrounding glaciolacustrine clays (see Bluemle 1967).
Coordinate Shift - Shift in the x- or/and y-coordinates values (see Coordinate System). Coordinate shifts are accomplished by adding or subtracting a constant from coordinate values.
Coordinate System - A reference system used to measure horizontal and vertical distances on a planimetric map. A coordinate system is usually defined by a map projection, a spheroid of reference, a datum, one or more standard parallels, a central meridian, and possible shifts in the x- and y- directions to locate x, y positions of point, line, and area feature.
Core [drill]. A cylindrical section of sediment or rock, usually 5-10 cm in diameter and up to several meters in length, taken as a sample of the interval penetrated by a core bit, and brought to the surface for geologic examination and/or laboratory analysis.
Correlation Coefficients - Is a number between -1 and 1 that measures the degree to which two variables are linearly related. If there is perfect linear relationship with positive slope between the two variables, the correlation coefficient will be 1; if there is positive correlation, whenever one variable has a high (low) value, so does the other. If there is a perfect linear relationship with negative slope between the two variables, there is a correlation coefficient of -1; if there is negative correlation, whenever one variable has a high (low) value, the other has a low (high) value. A correlation coefficient of 0 means that there is no linear relationship between the variables.
Coverage - A GIS spatial dataset that stores geographic features as Primary features (such as arcs, nodes, polygons and label points) and Secondary features (such as tics, map extent, links and annotation). Associated feature attribute tables describe and store attributes of the geographic features. Thus, a coverage is a set of thematically associated data considered as a unit. A coverage usually represents a theme such as soils, streams, roads or land use.
Crevasse Splay - A small alluvial fan or other outspread deposit formed where an overloaded stream breaks through a levee and deposits its material on the floodplain. A landform that can result when a natural (or artificial) levee is breached, usually during a flood, in one location. Upon passing through the breach, sediment-laden floodwaters disperse across the flood basin, depositing a lob of sediment. There can be different components to a crevasse splay, depending upon the magnitude of the discharge through the breach, the sediment load, etc. Most common is a crevasse splay channel that tends to form distributary channels farther away from the point of the breach. This can result in definition of discrete splay lobs. Also, some splay channels can have natural levee rises bounding them.
CRM - An abbreviation for Cultural Resource Management. CRM is most often applied to activities mandated by national or state laws. It can apply to cultural resources of any time period, historic and prehistoric, and either archaeological (in-the-ground) resources or standing structures.
Cross-Cutting Relations - A geologic principle that states that any geologic stratum or unit that is truncated or cross-cut by another geologic unit must be the older of the two units. For example, a terrace inset beneath a higher terrace is younger than the higher terrace because of the principle of down cutting relations in a stream system.
Cross-Section. (a) A diagram or drawing that shows features transected by a given plane; specif. a vertical section drawn at right angles to the longer axis of a geologic or geomorphic feature, such as the mean direction of flow of a stream. (b) An actual exposure or cut that shows transected geologic features.
Cusp [coast]. One of a series of sharp, seaward-projecting points of beach material, built by wave action and separated from its neighbors by smoothly curved shallow re-entrants. Cusps are spaced at more or less regular intervals along the shoreline, and generally at right angles to it; distance between them ranges from less than a meter to many kilometers. The term "beach cusp" is frequently and loosely used as a synonym.
Cultural Resources Management - A sequential review system designed to preserve archaeological or historic sites threatened by construction. (See Phase I Survey, Phase II Survey, Phase III Survey and Mitigation).
Data Conversion - The translation of data from one format to another. Often when data are moved from one system to another, some form of data conversion is required to convert the data to a format the receiving system can interpret. Sometimes it is necessary to have an intermediate format.
Database - A collection of data that is organized so that its contents can easily be accessed, managed, and updated. The most prevalent type of database is the relational database, a tabular database in which data are defined so that they can be reorganized and accessed in a number of different ways. A distributed database is one that can be dispersed or replicated among different points in a network. An object-oriented database is one that is congruent with the data defined in object classes and subclasses.
Datum - A set of parameters and control points used to accurately define the three-dimensional shape of the Earth. The datum defines a geographic coordinate system, which is the basis for a planar coordinate system.
Decision Rules - In many predictive modeling projects, statistical formulas that determine points along a continuous logistic transformation scale that permit decisions to be made about the presence or absence of archaeological resources. A predictive model in this sense is a decision rule that assigns a land parcel location to ‘archaeological resource present’ or ‘archaeological resource absent’ on the basis of the environmental characteristics of the location. In the MnModel project, decision rules divided modeled landscapes into categories high, medium, and low probability of archaeological resource present (see Continuous Logistic Transformation Scale).
Degrees of Freedom - A term used in statistics to characterize the number of independent pieces of information contained in a statistic. For example, if we begin with a random sample of n observations and estimate the mean by the sample average, we are left with only (n-1) independent measurements from which to estimate the variance or deviations around the mean. In a simple regression, where we estimate both an intercept and a slope, only (n-2) degrees of freedom remain to measure variability around the fitted line.
Delta. The low, nearly flat, alluvial tract of land at or near the mouth of a river, commonly forming a triangular or fan-shaped plain of considerable area, crossed by many distributaries of the main river, perhaps extending beyond the general trend of the coast, and resulting from the accumulation of sediment supplied by the river in such quantities that it is not removed by tides, waves, and currents. Most deltas are partly subaerial and partly below the water. The term was introduced by Herodotus in the 5th Century B.C. for the tract of land, at the mouth of the Nile River, whose outline broadly resembled the Greek capital letter "delta", D , with the apex pointing upstream.
Dependent Variable - Anything whose value, or presence or absence, depends on the values of other, independent, variables. In this project, the dependent variables are "archaeological resource present" and "archaeological resource absent." The goal of modeling is to determine which independent variables, or combinations of independent variables, most accurately and precisely predict the presence or absence of one or the other of these dependent variables.
Depositional Environment. The type of environment under which sediments are deposited (e.g., fluvial, eolian, glacial, high energy, low energy). The location of a cultural site in reference to the surrounding landscape plays an important factor in the changes that occur to it over time. Common natural processes that alter the site once it is abandoned include erosion and sedimentation. Lack of deposition may allow many cultures to exist on the same land surface over a great time span. Rapid deposition may diffuse those same cultures over a thick sedimentary sequence.
Depositional Environment Ranking. An assigned numeric value representing the type of energy, drainage, or other environmental factor that would affect cultural deposits or the use of the landscape by people. When multiplied by the age ranking the product is a landscape suitability ranking.
Derived Variable – In this project, a variable obtained by analysis of the original source data and used in modeling. For example, the derived variable distance to water is obtained by analysis of the data sources containing water bodies.
Distributary Pattern. (a) A divergent stream flowing away from the main stream and not returning to it, as in a delta or on an alluvial plain. It may be produced by stream deposition choking the original channel. (b) One of the channels of a braided stream; a channel carrying the water of a stream distributary.
Dune [geomorph]. A low mound, ridge, bank, or hill of loose, windblown granular material (generally sand), either bare or covered with vegetation, capable of movement from place to place but always retaining its characteristic shape.
Ecological Classification System (ECS) – ECS is part of a nationwide mapping initiative developed to improve our ability to manage all natural resources on a sustainable basis. This is done by integrating climatic, geologic, hydrologic, topographic, soil, and vegetation data. In this project, Phase 3 modeling was based on ECS subsections or combined subsections.
Environmental Variable - A characteristic of the environment that varies from place to place or from time to time. In this project, a set of variables representing selected environmental factors were used as the independent variables in the modeling process.
Eolian. (a) Pertaining to the wind; esp. said of such deposits as loess and dune sand, of sedimentary structures such as wind-formed ripple marks, or of erosion and deposition accomplished by the wind. (b) Said of the active phase of a dune cycle, marked by diminished vegetal control and increased dune growth.
Erosional Strath. An extensive undissected terrace-like remnant of a broad, flat valley floor that has undergone dissection following channel incision. This strath is cut into the underlying strata which may be bedrock, till, or other pre-existing material. Strath terrace is another term for this feature.
Floating Point - The term floating point is derived from the fact that there is no fixed number of digits before or after the decimal point; that is, the decimal point can float. A floating point number is a real number, a number that can contain a fractional part.
Floating Point Grid - A grid whose cell values are floating points (see grid).
Floodplain. (a) The surface or strip of relatively smooth land adjacent to a river channel, constructed by the present river in its existing regimen and covered with water when the river overflows its banks. It is built of alluvium carried by the river during floods and deposited in the sluggish water beyond the influence of the swiftest current. A river has one floodplain and may have one or more terraces representing abandoned floodplains. (b) Any flat or nearly flat lowland that borders a stream and that may be covered by its waters at flood stages; the land described by the perimeter of the maximum probable flood.
Gain Statistic – A measure of a model’s performance, in terms of the percentage of correct predictions, over chance. It ranges from 0 to 1, with 1 for a perfect model that predicts all possible instances with little known information and 0 for a model that predicts no better than by random chance.
GB - Gigabyte, 1000 or 1024 megabytes, depending on who is measuring. A megabyte is a million bytes, technically, 1024 kilobytes. A byte is a set of bits that represent a single character. Usually there are 8 bits in a byte, sometimes more, depending on how the measurement is being made. A bit is a single digit number in base-2, either a 1 or a zero, the smallest unit of computerized data.
Geodetic Datum - A model of the Earth used for geodetic calculations. Geodesy is the science of measuring the shape and size of the Earth, together with the determination of the exact position of particular points on its surface by taking the Earth's curvature into account.
Geographic Information System (GIS) - An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. It incorporates the essential elements of computer cartography and relational databases into one system and provides additional tools for manipulating and analyzing the data spatially.
Geomorphology. (a) The science that treats the general configuration of the Earth’s surface; specif. the study of the classification, description, nature, origin, and development of present landforms and their relationships to underlying structures, and of the history of geologic changes as recorded by these surface features. The term is esp. applied to the genetic interpretation of landforms, but has also been restricted to features produced only by erosion or deposition. The term was applied widely in Europe before it was used in the U.S., where it has come to replace the term physiography and is usually considered a branch of geology; in Great Britain, it is usually regarded as a branch of geography. (b) The science of both ancient and present day landscapes and how they evolved through time.
Giddings Soil Probe - A piece of hydraulic digging equipment similar to a drill-rig, but more cost effective and easier to operate and maneuver. The Giddings soil probe is limited to less than ten to fifteen meters depth.
Glaciofluvial. Pertaining to the meltwater streams flowing from wasting glacier ice and esp. to the deposits and landforms produced by such streams, as kame terraces and outwash plains; relating to the combined action of glaciers and streams.
Glaciolacustrine. Pertaining to, derived from, or deposited in glacial lakes; esp. said of the deposits and landforms composed of suspended material brought by meltwater streams flowing into lakes bordering the glacier, such as deltas, kame deltas, and varved sediments.
Global Positioning System (GPS) - A device for determining highly specific locational coordinates based on information transmitted by a constellation of 24 satellites orbiting the earth at a very high altitude.
Grid - A geographic data model represented as an array of equally sized square cells arranged in rows and columns. Each grid cell is referenced by it geographic x, y location and contains one data value, such as elevation.
Histogram -A graphic way of summarizing data that are measured on an interval scale (either discrete or continuous). Histograms are often used in exploratory data analysis to illustrate the major features of the distribution of the data in a convenient form. A histogram divides up the range of possible values in a data set into classes or groups. For each group, a rectangle is constructed with a base length equal to the range of values in that specific group, and an area proportional to the number of observations falling into that group. This means that the rectangles might be drawn of non-uniform height.
Holocene - see Quaternary Period. An epoch of the Quaternary period, from the end of the Pleistocene, approximately 10,000 years ago, to the present time; also, the corresponding series of rocks and deposits. When the Quaternary is designated as an era, the Holocene is considered to be a period.
Horizons [soil]. A layer of soil that is distinguishable from adjacent layers by characteristic physical properties such as structure, color, or texture, or by chemical composition, including content of organic matter or degree of acidity or alkalinity. Soil horizons are generally designated by a capital letter, with or without a numerical annotation ( e.g., A-horizon, C1-horizon).
Hydrology. The science that deals with global water (both liquid and solid), its properties, circulation, and distribution, on and under the Earth’s surface and in the atmosphere, from the moment of its precipitation until it is returned to the atmosphere through evapotranspiration or is discharged into the ocean. In recent years the scope of hydrology has been expanded to include environmental and economic aspects.
Ice-Block Kame Terrace. A subaerial or submerged ring-shaped terrace found around the periphery of ice-block lake basins thought to have formed as a result of glacial ice run-off depositing materials into the fosse or trough-like hollow that developed between the ice block and a high valley wall or moraine. The hollow may contain a glacial lake or a glacial river in which these glacial sediments are deposited. The hollow probably developed as a result of reflected or adsorbed heat from the moraine or valley wall.
Igneous rock. Said of a rock or mineral that solidified from molten or partly molten material, i.e. from a magma; also, applied to processes leading to, related to, or resulting from the formation of such rocks. Igneous rocks constitute one of the three main classes into which rocks are divided, the others being metamorphic and sedimentary.
Independent Variable - A variable in a functional relation whose value determines the value or values of other variables. For the predictive models, the independent variables are based on environmental factors such as proximity to water, slope, aspect, and proximity to various types of vegetation.
Integer Grid - A grid whose cell values are integers (see grid)
Integration (System) - Integration (from the Latin integer, meaning whole or entire) generally means combining parts so that they work together or form a whole. In information technology, integration during product development is a process in which separately produced components or subsystems are combined and problems in their interactions are addressed.
Kappa Statistic – A coefficient index to determine the agreement between two sets of categorical measurement. It corrects chance agreement and ranges from -1 to +1, with +1 meaning perfect agreement, -1 meaning perfect disagreement, 0 meaning no better than that expected due to chance. In this project, Kappa was used to describe the agreement between two models based on different halves of the data for same ECS subsection in Phase 3 modeling (see ECS and Phase 3).
Lacustrine. (a) Pertaining to, produced by, or formed in a lake or lakes; e.g., "lacustrine sands" deposited on the bottom of a lake, or a "lacustrine terrace" formed along its margin. (b) Growing in or inhabiting lakes; e.g., a "lacustrine fauna." (c) Said of a region characterized by lakes; e.g., a "lacustrine desert" containing the remnants of numerous lakes that are now dry.
Landform. Any physical, recognizable form or feature of the Earth’s surface, having a characteristic shape, and produced by natural causes; it includes forms such as plain, hill, terrace, slope, esker, and dune. Taken together, the landforms make up the surface configuration of the Earth.
Landscape. A section or expanse of natural scenery, usually that can be seen from a single view of point. In this project, landscape is the total landform representation of combined geographic factors such as soil, water, climate, vegetation, and geomorphology. (a) The distinct set of landforms, esp. as modified by geologic forces, that can be seen in a single view, e.g., glacial landscape. (b) [MnModel] A "major" landform or set of landforms generated by a particular geologic process; the term "major" refers to the relative size of landforms, which is on a sliding scale.
Landscape Suitability Ranking (LSR). (a) A ranking used to evaluate the potentials for the land surface and subsurface intervals to have and preserve in situ cultural deposits based upon stratigraphic ages and either post-depositional or depositional environments. This ranking does not predict archaeological site locations, it predicts landscapes and paleolandscapes that could contain or not contain in situ sites. (b) The numerical product of the age ranking and depositional environment ranking.
Legend - The reference area on a map that lists and explains the colors, symbols, line patterns, shadings, and annotation used on the map. The legend often includes the scale, origin, orientation, and other map interpretation information.
Levee [streams] (a) see natural levee. (b) An artificial embankment built along the bank of a watercourse or an arm of the sea, to protect land from inundation or to confine streamflow to its channel.
Lithic Scatter - A type of archaeological site marked by the presence of material made of modified stone. In Minnesota, these are commonly sites small in size composed of a low density of flaked or chipped stone, the by-products of stone tool manufacture. On rare occasions, a lithic scatter may be very large and sometimes contain fire-cracked rock. Lithic scatters are different from artifact scatters, which contain artifacts from more than one material class (e.g. stone and ceramic).
Lithofacies. A lateral, mappable subdivision of a designated stratigraphic unit, distinguished from adjacent subdivisions on the basis of lithology, including all mineralogic and petrographic characters and those paleontologic characters that influence the appearance, composition, or texture of the rock; a facies characterized by particular lithologic features. Laterally equivalent lithofacies may be separated by vertical arbitrary-cut-off planes, by intertonguing surfaces, or by gradational changes.
Loess. A widespread, homogeneous, commonly nonstratified, porous, friable, slightly coherent, usually highly calcareous, fine-grained blanket deposit, consisting predominantly of silt with subordinate grain sizes ranging from clay to fine sand. Loess is windblown dust of varying ages, carried from desert surfaces, alluvial valleys, and outwash plains, or from unconsolidated glacial or glaciofluvial deposits uncovered by successive glacial recessions but prior to invasion by a vegetation mat. The mineral grains, composed mostly of silica and associated heavy minerals, are fresh and angular, and may be held together by calcareous cement.
Logistic Regression - A nonparametric statistical procedure that, among other things, can be used to explore the varying strength of the association of a dependent variable, measured as presence or absence of a phenomenon, and multiple independent variables. Logistic regression techniques have been widely used in archaeological modeling because they are robust (i.e., they can handle any distributional type) and can accommodate nominal, ordinal, and interval independent variables.
Mann-Whitney U Test - The Mann-Whitney Test is one of the most powerful of the nonparametric tests for comparing two populations. It is used to test the null hypothesis that two populations have identical distribution functions against the alternative hypothesis that the two distribution functions differ only with respect to location (median), if at all. The Mann-Whitney test does not require the assumption that the differences between the two samples are normally distributed. In many applications, the Mann-Whitney Test is used in place of the two-sample t-test when the normality assumption is questionable. This test can also be applied when the observations in a sample of data are ranks, that is, ordinal data rather than direct measurements.
Marl. (a) An old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under marine or esp. freshwater conditions. (b) A soft, grayish to white, earthy or powdery, usually impure calcium carbonate precipitated on the bottoms of present-day freshwater lakes and ponds largely through the chemical action of aquatic plants, or forming deposits that underlie marshes, swamps, and bogs that occupy the sites of former (glacial) lakes. The calcium carbonate may range from 90 percent to less than 30 percent.
Mean - The mean is one of several indices of central tendency that statisticians use to indicate the point on the scale of measures where the population is centered. The mean is the average of the scores in the population. Numerically, it equals the sum of the scores divided by the number of scores. It is of interest that the mean is the one value that, if substituted for every score in a population, would yield the same sum as the original scores, and hence it would yield the same mean.
Meander [streams]. n. (a) One of a series of regular freely developing sinuous curves, bends, loops, turns, or windings in the course of a stream. It is produced by a mature stream swinging from side to side as it flows across its floodplain or shifts its course laterally toward the convex side of an original curve. (b) valley meander.--v. To wind or turn in a sinuous or intricate course; to form a meander.
Median -The median is one of several indices of central tendency that statisticians use to indicate the point on the scale of measures where the population is centered. The median of a population is the point that divides the distribution of scores in half. Numerically, half of the scores in a population will have values that are equal to or larger than the median and half will have values that are equal to or smaller than the median.
Metamorphic Rock. Any rock derived from pre-existing rocks by mineralogical, chemical, and/or structural changes, essentially in the solid state, in response to marked changes in temperature, pressure, shearing stress, and chemical environment, generally at depth in the Earth's crust.
Mitigation - Steps taken to reduce the impact of a construction project or other disturbance on an archaeological or historic site. Mitigation can range from site avoidance to excavation and thorough study.
Model - A representation of reality used to simulate a process, understand a situation, predict an outcome, or analyze a problem. A model is structured as a set of rules and procedures. Some models, or their results, can be represented as physical representations, i.e. scale-models, graphic models, or cartographic models. A working hypothesis or precise simulation, by means of description, statistical data, or analogy, of a phenomenon or process that cannot be observed directly or that is difficult to observe directly. Models may be derived by various methods (e.g., by computer, from stereoscopic photographs, or by scaled experiments).
Multiple Component Sites - Precontact archaeological sites that contain evidence for the presence of two or more components or occupations. Occupations can occur over short or long time periods, marked by temporally diagnostic artifacts or features assigned to more than one time period.
National Register of Historic Places Criteria - Criteria established by the Secretary of the Interior for properties or sites to be included on the National Register of Historic Places. Refer to Bulletin 16A for a description of these criteria.
Natural Levee. A long broad low ridge or embankment of sand, silt, or other material, built by a stream on its floodplain and along both banks of its channel during flood stage when the coarser sediment is deposited as a result of suddenly decreased velocity once spilling over to the floodplain.
"Nodata" Values - Missing values in a grid database. "Nodata" values may represent missing data or may be used to occupy grid cells outside the area of interest.
Noise - Records in a database containing random or erroneous data, or data that otherwise do not follow the dominate patterns of other data in the same database. In this project, noise refers to sites that are in locations environmentally different than locations of the majority of sites in the same database. They may be in different environments because they are older and the environment has changed, the activities they represent were less common or more localized and required different resources, or because their coordinates were incorrectly recorded.
Nominal Variable - A variable is said to be nominal if the values/observations belonging to it can be assigned a code in the form of a number, where the numbers are simply labels. You can count but not order or measure nominal data. For example, in a data set males could be coded as 0, females as 1; marital status of an individual could be coded as Y if married, N if single.
Nonsite - A location where sites are not found. Ideally, a nonsite should have been surveyed to verify that no sites are present. This project, however, used random points as non-sites because surveyed locations were found to inadequately represent the total environment.
Normal Form - A relation in a relational database is said to be in normal form if it satisfies certain design standards. There are five widely accepted data design standards referred to as normal forms. Making tables match these standards is called normalization.
North American Datum (NAD) - The official reference ellipsoid used for the primary geodetic network in North America (see datum).
Particle-Size Analysis - An examination of the three different particle sizes in sediments or soils (sand, silt, and clay) in order to describe and interpret the natural processes responsible for their deposition. For example, fine particles overlying coarser particles are indicative of flood deposits that were deposited under decreasing energy.
Pattern Recognition - The identification of a pattern in the distribution of particular environmental variables across landscapes. Since some aspects of these patterns may be highly correlated with archaeological resource presence or absence, their identification is an essential component of predictive archaeological resource modeling projects in which classification techniques are used.
Patterned Variation - The correlated behavior of spatial phenomena; a descriptive phrase that defines the core attribute of spatial autocorrelation (see Spatial Autocorrelation).
Pediment. A broad gently sloping glacial drift or rock-floored erosion surface or plain of low relief, typically developed by subaerial agents (including running water) in an arid or semiarid region at the base or side of an abrupt and receding hillside and occasionally buried by older alluvial deposits. They may be bare but are more often partly mantled with a thin discontinuous veneer of alluvium derived from the upland masses and in transit across the surface. The longitudinal profile of a pediment is normally slightly concave upward.
Pedologic. A term used in soil classification for the collection of natural earthy materials on the Earth’s surface, in places modified or even made by man, containing living matter, and supporting or capable of supporting plants out-of-doors. The lower limit is normally the lower limit of biologic activity, which generally coincides with the common rooting of native perennial plants.
Performance - A function of the ratio between the number of sites or surveyed places predicted and the proportion of the landscape categorized as having potential for archaeological resources or for having been surveyed (high and medium probability areas in these models). See Gain Statistic.
Peripheral - Any computer device that is not part of the essential computer (the processor, memory, and data paths) but is situated relatively close by. A near synonym is input/output (I/O) device. Some peripherals are mounted in the same case with the main part of the computer, as are the hard drive, CD-ROM drive, and network interface cards. Other peripherals, such as the printer and image scanner, are outside the computer case, attached by a wired or wireless connection.
Phase 1 – The first phase of this project, from May 1995 to December 1996. In this phase, initial models were built for 29 counties using archaeological data from probabilistic surveys meeting standards defined by the BRW Cultural Resources staff and MnModel Research Director. Non-sites were negative survey points. The method for modeling was logistic regression. The selection of independent variables had a subjective element, as the statistical tool used (Arc/Info GRID) could not perform stepwise variable selection. For these models, sites representing isolated finds or single artifacts were excluded.
Phase 2 – The second phase of this project lasting from January 1997 to September 1997. In this phase, models were built using archaeological data from probabilistic and qualified CRM surveys. Non-sites were truly random points generated by the GIS. Models were built based on available environmental variables for archaeological resource regions (see Archaeological Resource Region) of the entire state. At least two models were run for each region. The first excluded single artifacts from the training data. The second excluded both single artifacts and lithic scatters. The statistical method used was logistic regression, however, the selection of independent variables was objective and the model tool used (S-PLUS) could perform stepwise variable selection.
Phase 3 – The final and third phase of this project from October 1997 to November 1999. In this phase, models were built on environmental variables available for each ECS (see Ecological Classification System) subsection and combined ECS subsections. Additional variables were included in the process. The modeling method used in this phase is the same as Phase 2. Besides preliminary site and survey models created using halves of all sites except single artifacts and halves of surveyed places, final site and survey models were generated using all sites except single artifacts and all surveyed places. Final deliverables and the draft final report were developed in this phase.
Pleistocene. An epoch of the Quaternary period, after the Pliocene of the Tertiary and before the Holocene; also, the corresponding worldwide series of rocks. It began two to three million years ago and lasted until the start of the Holocene some 10,000 years ago. When the Quaternary is designated as an era, the Pleistocene is considered to be a period.
Pollen Diagram. Any diagram of pollen abundance showing stratigraphic fluctuation; strictly, the graphical presentation of relative abundances of various genera of pollen and spores at successive levels of cores of Quaternary sediment studied in pollen analysis.
Potential - Capable of being, but not yet realized. With respect to archaeological predictive models, places with high site potential are considered likely to contain archaeological properties, but these may not yet have been discovered.
Precision – 1) The ability of an archaeological predictive model to correctly predict site presence at a certain percentage of a population of known sites (the test population), while mapping substantially less than this percentage of the landscape to medium or high archaeological sensitivity zones. A model that indicates high archaeological site potential at every location in a region would be 100 percent accurate, as it would accurately predict 100% of the test population of sites, but would lack precision. An archaeological predictive model must be not only accurate but also precise in its predictions. 2) In spatial data, the ability to precisely represent locations of geographic features and attributes of the features. Spatial precision is expressed as a distance that is the margin of error between the feature's true location and its location as represented in a spatial database. For data digitized from a 1:24,000 scale source map, the expected precision is +/- 40 feet.
Precontact - Archaeological site locations that predate 1650 and the active beginning of the fur trade in Minnesota. See Contact Period.
Prediction - The act of foretelling. An archaeological predictive model predicts the potential or probability for the presence of archeological sites. In MnModel, a known archaeological site was said to be "predicted" by the model if it fell within either the high or medium probability class.
Preliminary Site Probability Model – Phase 3 model showing the predicted spatial occurrence of archaeological sites. Preliminary models are based on a randomly selected half of the database (half of all known sites excluding single artifacts and half of all random points within modeling region). Preliminary models were used for testing model performance and stability and were later replaced by site probability models based on the entire database.
Preliminary Survey Probability Model – Phase 3 model showing the spatial occurrence of environments similar to those that have had archaeological surveys. Preliminary models are based on a randomly selected half of the database (half of all recorded survey locations and half of all random points within each modeling region). Preliminary models were used for testing model performance and stability and were later replaced by survey probability models based on the entire database.
Primary Key - In database management systems, a key is a field used to sort data. Most database management systems allow more than one key so that records can be sorted in different ways. One of the keys is designated the primary key, and must hold a unique value for each record.
Probability - A quantitative description of the likely occurrence of a particular event. Probability is expressed on a scale between 0 and 1; a rare event has a probability close to 0, a very common event has a probability close to 1. The probability of an event has been defined as its long-run relative frequency.
Projection - A mathematical model that transforms the locations of features on the Earth's surface to locations on a two-dimensional surface. Because the Earth is three-dimensional, a projection must be used to depict a map in two dimensions. Some projections preserve shape, while others preserve accuracy of area, distance, or direction.
Public Land Survey (PLS) - Federally sponsored surveys that imposed an imaginary grid over US states. The fundamental local unit of the grid is a 40-acre parcel (quarter-quarter section). Higher level local units include the section (one square mile), township, and range. The surveyors’ descriptions of the vegetation and water resources around them are today a valuable source of information about the natural environment of North America, for the surveys generally took place prior to major landscape modifications, such as farming or logging. Most Public Land Surveys in Minnesota were conducted in the last half of the 19th century.
P-value - The probability value of a statistical hypothesis test. The probability of getting a value of the test statistic as extreme as or more extreme than that observed by chance alone, if the null hypothesis H0, is true. In other words, the probability of wrongly rejecting the null hypothesis if it is in fact true. In use, the p-value is compared with the significance level at which we would determine to reject the null hypothesis. If the p-value is smaller than the accepted significance value, the result of the test is significant. For example, if the null hypothesis were to be rejected at p = 0.05, then p values less than 0.05 would suggest that the null hypothesis is unlikely to be true. The smaller the p-value, the more convincing is the rejection of the null hypothesis.
Quaternary Period - The geologic period ranging from two million years ago to the present. The Quaternary is divided into two epochs: the Holocene (10,000 years ago to the present) and the Pleistocene (two million to 10,000 years ago).
Radiocarbon Dating. A method of determining an age in years by measuring the concentration of carbon-14 remaining in an organic material, usually formerly living matter, but also water bicarbonate, etc. The method, worked out by Willard F. Libby, U.S. chemist, in 1946-1951, is based on the assumption that assimilation of carbon-14 ceased abruptly on removal of the material from the Earth’s carbon cycle (i.e., on the death of an organism) and that it thereafter remained a closed system. Most carbon-14 ages are calculated using a half-life of 5730+40 years or 5568+30 years. Thus the method is useful in determining ages in the range of 500 to 30, 000 or 40,000 years, although it may be extended to 70,000 years by using special techniques involving controlled enrichment of the sample in carbon-14.
RAM - Acronym for Random Access Memory, a form of primary computer storage that allows direct read and write operations. RAM storage is generally a very high-speed medium that requires constant power to avoid data loss.
Range - One of several indices of variability that statisticians use to characterize the dispersion among the measures in a given population. The range is the distance between the highest and lowest score. Numerically, the range equals the highest score minus the lowest score.
Region - When used with reference to Phase 3, a geographic modeling unit that may consist of an ECS subsection or set of subsections.
Relational Database - A method of structuring data as collections of tables that are logically associated to each other by shared attributes. Any data element can be found in a relation by knowing the name of the table, the attribute (column) name, and the value of the primary key.
Relational Database Management System (RDBMS) - Software used to create, update, and administer a relational database. An RDBMS takes Structured Query Language (SQL) statements entered by a user or contained in an application program and creates, updates, or provides access to the database. Some of the best-known RDBMS's include Microsoft's Access, Oracle's Oracle7, and Computer Associates' CA-OpenIngres.
Resolution - The minimum distance between two objects that can be distinguished by a sensor, or depicted at a given map scale. The minimum size of a feature that can be reliably distinguished by a remote sensing system, or depicted in a raster data set. Resolution acts as a measure of the sharpness of an image or the level of detail depicted in spatial data.
Ripples. (a) An undulatory surface or surface sculpture consisting of alternating subparallel small-scale ridges and hollows formed at the interface between a fluid and incoherent sedimentary material (esp. loose sand). It is produced on land by wind action and subaqueously by currents or by the agitation of water in wave action, and generally trends at right angles or obliquely to the direction of flow of the moving fluid. It is no longer regarded as evidence solely of shallow water.
Root Mean Square Error - A measure of the dispersion of points around a center. It is mathematically the spatial equivalent to the standard deviation. The lower the RMS error, the more accurate the digitizing or transformation.
Sample - A sample is a group of units selected from a larger group (the population). A sample is studied to draw valid conclusions about the larger group, because the population is too large to study in its entirety. The sample should be representative of the general population. This is best achieved by random sampling. Also, before collecting the sample, it is important that the researcher carefully and completely defines the population, including a description of the members to be included.
Scale - The reduction needed to display a representation of the Earth surface on a map. A statement of a measure on the map and the equivalent measure on the Earth surface, often expressed as representative fraction of distance, such as 1:24,000 (one unit of distance on the map represents 24,000 of the same units on the Earth). Map scale can also be expressed as a statement of equivalence using different units; for example, 1 inch = 1 mile or 1 inch = 2,000 feet.
Sedimentary Rock. (a) A rock resulting from the consolidation of loose sediment that has accumulated in layers; e.g., a clastic rock (such as conglomerate or tillite) consisting of mechanically formed fragments of older rock transported from its source and deposited in water or from air or ice; or a chemical rock (such as rock salt or gypsum) formed by precipitation from solution; or an organic rock (such as certain limestones) consisting of the remains or secretions of plants and animals.
Significance - The significance level of a statistical hypothesis test is a fixed probability of wrongly rejecting the null hypothesis H0, if it is in fact true. It is the probability of a type I error and is set by the investigator in relation to the consequences of such an error. That is, the significance level should be as small as possible in order to protect the null hypothesis and to prevent, as far as possible, the investigator from inadvertently making false claims. The significance level is usually denoted by:
Significance Level = P (type I error). Usually, the significance level is chosen to be 0.05 (or equivalently, five percent).
Simple Random Survey – Survey using simple random sampling, a selection method that makes choices strictly according to probability or chance, with no influence by the selector. In this survey, each member of the population has an equal chance of being included in the sample.
Single Artifact - An archaeological artifact found alone, without any other artifacts nearby. The Office of the State Archaeologist in Minnesota recognizes single artifacts as archaeological sites.
Single Component Sites - Archaeological sites that contain evidence for the presence of one component or occupation. Occupations can occur over a short or long period of time, marked by temporally diagnostic artifacts or features assigned to one time period.
Site Probability Model – Model showing the predicted spatial occurrence of archaeological sites. Phase 3 site probability models are based on the entire database consisting of all known archaeological sites except single artifacts and all randomly selected points (non-sites) within each modeling region. No data remained to test these models. Test were performed on preliminary site probability models.
Slope - A measure of change in surface value over distance, expressed in degrees or as a percentage. For example, a rise of two meters over a distance of 100 meters describes a two percent slope with an angle of 1.15. Mathematically, slope is referred to as the first derivative of the surface.
Slump. (a) A landfall characterized by a shearing and rotary movement of a generally independent mass of rock or earth along a curved slope from which it descends, and by backward tilting of the mass with respect to that slope so that the slump surface often exhibits a reversed slope facing uphill. (b) The mass of material slipped down during, or produced by, a slump.
Smirnov (Kolmogorov-Smirnov) Test - A non-parametric statistical test used to determine if two separate samples could have been drawn from the same population or from populations with the same distributions.
Spatial Autocorrelation - Patterned variation among spatial phenomena. The great majority of statistical inferential procedures used in archaeological predictive modeling assume independent observations, that is, that the values of some observations cannot be predicted (at a better than random chance) from the known values of other values. Since spatial phenomena generally exhibit patterned variation, or autocorrelation, the assumption of statistical independence is violated. As a result, statistical significance tends to be overestimated. In models of this kind, then, the effect of autocorrelation has to be controlled or at least taken into account.
Spearman's Rank Order Correlation Coefficient - A correlation coefficient based on rank order rather than absolute value. It is usually calculated on occasions when it is not convenient, economic, or even possible to give actual values to variables, but only to assign a rank order to instances of each variable. It may also be a better indicator that a relationship exists between two variables when the relationship is non-linear. It is not as sensitive to outliers and nonnormality as the standard Pearson correlation coefficient.
Spit. (a) A small point or low tongue or narrow embankment of land, commonly consisting of sand or gravel deposited by longshore drifting and having one end attached to the mainland and the other terminating in open water, usually the sea; a fingerlike extension of the beach. (b) A relatively long, narrow shoal or reef extending from the shore into a body of water.
S-Plus - Statistical software developed by MathSoft (now Insightful Corp.). S-Plus is an object-oriented programming language based on S, initially developed by Bell Lab. With both the Unix and Windows versions, it is widely used for data analysis and research. S-Plus offers great flexibility in data analysis and programming.
Stability - With reference to predictive models, a measure of the similarity of different models developed using different portions of the same database. The higher the stability, the greater the assurance that the models' predictions are correct for the data from which they were derived.
Standard Deviation -One of several indices of variability that statisticians use to characterize the dispersion among the measures in a given population. To calculate the standard deviation of a population it is first necessary to calculate that population's variance. Numerically, the standard deviation is the square root of the variance. Unlike the variance, which is a somewhat abstract measure of variability, the standard deviation can be readily conceptualized as a distance along the scale of measurement.
Stepwise - In a step-by-step arrangement or sequences. In this project, a stepwise procedure was used to select the best independent variables for each model, reducing variables one by one until the total number of variables equaled 30.
Stepwise Regression - A multivariate regression procedure that seeks the 'best' model in stages. A list of independent variables is repeatedly searched for the best combination of variables to include in the model.
Strath terrace - As used in this report, an erosional surface (see Terrace) that is erosional in origin, developed on bedrock or glacial till.
Stratigraphic Unit. A stratum or body of adjacent strata recognized as a unit in the classification of a rock sequence with respect to any of the many characters, properties, or attributes that rocks may possess (ISG, 1976, p. 13), for any purpose such as description, mapping, and correlation. Rocks may be classified stratigraphically on the basis of lithology (lithostratigraphic units), or properties (such as mineral content, radioactivity, seismic velocity, electric-log character, chemical composition) in categories for which formal nomenclature is lacking.
Stratigraphy. A branch of geology dealing with the classification, nomenclature, correlation, and interpretation of stratified rocks. (a) The science of rock strata. It is concerned not only with the original succession and age relations of rock strata but also with their form, distribution, lithologic composition, fossil content, geophysical and geochemical properties -- indeed, with all characters and attributes of rocks as strata; and their interpretation in terms of environment or mode of origin, and geologic history. All classes of rocks, consolidated or unconsolidated, fall within the general scope of stratigraphy. (b) The arrangement of strata, esp. as to geographic position and chronologic order of sequence.
Stratified Random Survey – Survey using stratified random sampling. The population is first divided into strata, groups of individuals that are similar in some way that is important to the response (i.e. men and women). Separate simple random samples are then selected from each stratum and combined to form the full sample.
Survey Implementation Model – Composite of the Phase 3 site probability model and survey probability model. It provides information about the spatial concurrence of site and survey probabilities using the following archaeological site probability classes: unknown, suspected medium, suspected high, possibly low, possibly medium, possibly high, low, medium, and high.
Survey Probability Model – Phase 3 model showing the spatial occurrence of environments similar to those that have had archaeological surveys. Phase 3 survey probability models are based on the database of all recorded survey locations and all random points within each modeling region). The models illustrate survey bias and map areas in one of the three archaeological survey probability categories: high, medium, and low.
Template - A pattern or gauge used in duplicating something. A digital map layout containing neatlines, north arrow, logos, and other cartographic map elements for a common map series. A digital map containing common feature boundaries, such as land-water boundaries, for use as a starting place in automating the creation of other digital maps. Templates save time and increase the precision of topological overlays.
Terrace [geomorph]. (a) Any long, narrow, relatively level or gently inclined surface, generally less broad than a plain, bounded along one edge by a steeper descending slope and along the other by a steeper ascending slope; a large bench or steplike ledge breaking the continuity of a slope. The term is usually applied to both the lower or front slope (the riser) and the flattish surface (the tread), and it commonly denotes a surface of a valley-contained, aggradational form composed of unconsolidated material as contrasted with a bench eroded in solid rock or till, for example. A terrace commonly occurs along the margin and above the level of a body of water, marking a former water level; e.g., a stream terrace. (b) A term commonly but incorrectly applied to the deposit underlying the trend and riser of a terrace, esp. the alluvium of a stream terrace; "this deposit ... should more properly be referred to as a fill, alluvial fill, or alluvial deposit, in order to differentiate it from the topographic form" (Leopold et al. 1964, p. 460).
Thematic Layer - An individual GIS map layer, such as the spatial distribution of major soil types, the spatial distribution of early historic properties, or the distribution of water bodies. Thematic layers may be used directly as variables, and multiple additional variables can be derived from a single thematic layer.
Tile - A spatial unit by which geographic data are organized, subdivided, and stored in a map library. Tiles subdivide the area covered by a map library and organize the library data by location (e.g., counties may be the tiles in a statewide database). A tile can be a regular geometric shape (e.g., a rectangular map sheet) or an irregular shape such as a county boundary.
Topography. (a) The general configuration of a land surface or any part of the Earth’s surface, including its relief and the position of its natural and man-made features. (b) The natural or physical surface features of a region, considered collectively as to form; the features revealed by the contour lines of a map.
Transect - A path across a parcel of land within which a search for archaeological sites was carried out through a visual scanning of exposed soil (e.g., in a plowed field) or through shovel testing. Parallel, usually straight transects were used in the project to search for sites in 1995 and 1996.
Universal Transverse Mercator (UTM) – A grid system that is widely adopted for topographic maps, satellite imagery, natural resource databases, and other applications that require precise positioning.
Upland. A general term for elevated land above the low areas along a stream or between hills; any elevated region from which rivers gather drainage. Also, an area of land above flood level, or not reached by storm tides. MnModel also uses the term for areas that were not differentiated but still within or adjacent to the mapped areas.
Value attribute table (VAT) - A table containing attributes for a grid. The VAT contains one record for each unique value assigned to cells in the grid. Each VAT record contains a cell value, which functions as the primary key, and a count of the cells with that value. Additional user attributes can be added to the table.
Variance - One of several indices of variability that statisticians use to characterize the dispersion among the measures in a given population. To calculate the variance of a given population, calculate the mean of the scores, measure the amount that each score deviates from the mean, and then square that deviation. Numerically, the variance equals the average of the several squared deviations from the mean.
Vector - A format for processing and displaying graphic and geographic data. Vector GIS data consist of coordinates indicating the geographic position of features represented by points, lines, and the boundaries of areas. An ARC/INFO Coverage is a type of vector data storage.
Wave-Cut Platform. A gently sloping surface produced by wave erosion, extending far into the sea or lake from the base of the wave-cut cliff. It represents both the wave-cut bench and the abrasion platform.
Y- shift – A coordinate shift in the Y (north-south) axis (latitude). The UTM coordinate system records y-coordinate values between 4 million and 5 million meters in Minnesota. This requires coordinates to be stored as more than seven digits to maintain spatial accuracy. To accommodate GIS software that cannot store coordinates in so many digits, a constant may be subtracted from each y-coordinate, producing a controlled shift or offset in the data. The standard shift in Minnesota is 4.7 million meters.