How we obtain various types of mapping data
The GIS Basemap Unit maintains the Geographic Information System (GIS) layers found on MnDOT's Interactive Basemap. In the late 1980's, MnDOT began researching the potential offered by GIS technology for its own needs and services. In 1992, creation of a series of internal task forces and consultation with the state Land Management Information Center (LMIC) resulted in a decision to incorporate CAD digitizing efforts into a statewide seamless basic core of geography that would provide a means for relating MnDOT spatial data to other spatial data. The GIS software chosen was Environmental System Research Institute's (ESRI) Arc/Info. CAD digitizing continued, but at an accelerated pace in order to complete statewide 1:24,000 scale coverage within 18 months. MnDOT also switched projection formats, from using State Plane Coordinates zone specific, NAD83 to Universal Transverse Mercator (UTM) Minnesota extended Zone 15, NAD83 coordinates.
In March of 1993, the MnDOT Cartographic Unit began converting and updating the one-third of statewide quad coverage already completed and accelerated digitizing of the state's remaining quad coverage. By the end of 1994, digitizing had been completed and work began on creating Arc/Info GIS coverages from the CAD line work. In 1996, MnDOT produced its first State of Minnesota GIS BaseMap on CD-ROM. While the BaseMap files did not contain attribution for all of its 21 data layers, it did fulfill MnDOT's initial goal of providing a data set on which to display MnDOT geospatial information. In preparation for BaseMap 2000, a concerted effort was made to capture the alignment of all local city streets built since the release of the original BaseMap and complete attribution for Municipal State Aid Streets (MSAS), County Roads (CR), railroads, and civil townships and selected state/federal agency administrative boundaries (forests, parks, etc.).
Currently, MnDOT provides annual updates to the BaseMap. The Minnesota Trunk Highway (TH) and County State Aid System (CSAH) alignment and route coverages as well as municipal boundary coverage are improved each year. Changes to roads come from several sources including county engineers, city engineers, the MnDOT State Aid office (who manage county state aid highways and municipal state aid streets), the most recent aerial photos available, and construction plans.
Roadway attributes included in BaseMap are the TIS code, street names, mileage information, and the county code. The TIS code is derived from the route system, county, or municipal code and the route number. Route numbers are signed numbers for trunk highways, county state aid roads, and county roads; internally assigned numbers for municipal state aid streets; and numerically assigned for all other route systems. The mileage assigned to routes is based on true mileage and reference posts for all trunk highways, and cartographic length for other route systems. For divided roadways, the mileage is based from the increasing lanes, or the direction of travel with increasing mileage.
The Enhanced Interactive BaseMap
Now available online is the enhanced Interactive BaseMap, the result of a two-year effort to update the entire public transportation system. This included adding new roads for all systems, providing additional and updated attribute information, creating metadata for individual data sets, and building routes for the entire system.
The Geographic Information & Mapping (GIM) Unit generates several map products for the State of Minnesota. The most popular is the Official State Highway Map, which is produced every two years. The unit also creates and maintains maps for all of Minnesota’s 87 counties and 853 cities, as well as produces a unique series of 56 maps covering the Twin Cities metro area, called the Metropolitan Area Street Series.
Each map produced by the GIM Unit contains a number of recognizable features such as roads, bridges, legislative boundaries, water attributes, public facilities, and text annotation. Although many spatial layers exist on every map, there are two features of emphasis-- roadway systems and corporate data. Roadway systems are major or minor highways, roads, streets, and railroads. Corporate data are the municipal (city) boundaries that depict the exact border between two cities or a city and a county. Due to the physical limitations of producing maps at scale for visual reference, not all features are included on every map.
Official State Highway Map
The primary purpose of the Official State Highway Map is to portray the major features of the transportation system in Minnesota-- major roads and corresponding route systems. Additionally, the map shows state and county legislative boundaries, major cities, unincorporated places, state and national parks, major railroads, airports, and other miscellaneous features. Changes in corporate limits that affect cities with populations over 25,000 are also depicted. A few unique elements that can be found on the State Highway Map are the city-to-city mileage chart, the city finder index, and various points of interest throughout the state. The product is released every two years on odd years and is available in both paper and digital formats using the information below:
- For a free paper copy, email the Explore Minnesota Tourism Office at firstname.lastname@example.org or call them at 1-888-TOURISM (868-7476)
- For a digital copy, visit http://www.dot.state.mn.us/statemap or email Jeff Saholt at email@example.com
County Maps are updated annually using information sent to the GIM Unit from each county in Minnesota. The chief purpose of the maps is to display all county-level planimetric information needed for highway planning throughout the state. Map scales vary due to the difference in county size, but a commonly used scale is 1 inch = approximately 0.5 mile. Priority is given to higher route systems (Interstates, US Highways, Minnesota Highways, County State Aid systems) when all roads cannot be mapped within a county.
Municipality (City) Maps
The main goal of Municipality (City) Maps is to portray the state transportation system at city-level detail. These maps are updated annually and show all route systems, including all city streets and private roads. Map scales may vary due to the difference in city size, but a commonly used scale range is approximately 1 inch = approximately 1/6 to 1 mile.
Cities over 5,000 in population are mapped on their own sheet; however, cities under 5,000 in population are located on sheets containing two or more city maps. The reason for distinction between city populations is because municipalities over 5,000 are eligible for funding from the Municipal State Aid System (MSAS) whereas municipalities under 5,000 are not.
Metro Street Series
The Metro Street Series is a group of 56 individual maps (with an accompanying reference grid map) covering the seven-county metro area and a portion of the surrounding area. The series is updated annually and is produced at a detailed scale of 1 inch = approximately 1/4 mile. The primary reason for producing the large-scale series is to depict the Metro Area’s busy roadway system for planning and reference purposes. The major elements included on each map are all road systems, municipal boundaries, and water features. This series is different from other GIM Unit products because roads are symbolized as single lines instead of the usual casing (where thicker lines represent higher volume roads).
General Map Update Methods
The GIM unit is responsible for keeping an updated record of roadway systems throughout Minnesota and corporate data for every municipality in the state. Every two years, the MnDOT Districts send a request for information in the form of paper or digital maps to all counties and municipalities. Each county or city representative outlines any changes that have occurred in the previous two years and returns the legal descriptions and map to MnDOT. As ordered by Minnesota statute, certain adjustments such as MnDOT commissioner's orders, turnback resolutions, and state aid orders require further verification and documentation before becoming official. Once a change is verified through the proper channels, the GIM staff updates the map as required.
The GIM unit maintains a comprehensive file of all annexation documents we receive. These documents are available for public use and are located in the Office of Transportation System Management on Third Floor North of MnDOT’s Central Office.
For digital records of municipal boundary changes, please visit the Municipal Boundary Adjustment Unit website at http://www.mba.state.mn.us/
Updating the GIM Unit’s various map products is a comprehensive and ongoing process that requires a collaborative effort. Staying up-to-date depends a great deal on the unit’s diligence in tracking trunk highway projects, staying updated on state aid funding changes, and verifying feature locations using aerial photography. But just as important is the cooperation of MnDOT district offices, other state departments, and local governments. All in all, it is the combination of MnDOT’s proactive measures and the assistance of other government entities that allows the GIM Unit to produce the best map product possible.