Michigan Department of Transportation: High-Accuracy Large-Scale Mapping
The Michigan Department of Transportation (MDOT) engineers required large-scale, high-accuracy topographic and planimetric mapping for design and construction plans for an ongoing improvement project along the I-94 highway corridor in downtown Detroit. The presence of high-rise buildings on both sides of the highway and the nearby Detroit airport necessitated the use of a helicopter instead of a fixed-wing aircraft to acquire 1”=80’ scale vertical aerial photography as a data source for high-accuracy mapping.
AeroMetric coordinated field and aerial surveys to provide the topographic mapping required for design and construction documents. To provide the required horizontal map feature detail and vertical accuracy of elevations, a helicopter platform was employed for the acquisition of color aerial photos. A relatively dense control network was established for the mapping, map checks and future construction of the project.
A local survey company familiar with the existing control in the area and MDOT Specifications performed the necessary photo control and “pick up surveys” for underground utility features, property ties, etc. Aerial survey is safer and more cost effective than closing lanes for field surveys to acquire data.
Using the digital imagery, control, and the aerotriangulation solution, AeroMetric generated a digital terrain model (DTM) meeting the MDOT mapping specifications. From the DTM, a check contour dataset was generated with a two-foot contour interval. This dataset was designed to allow MDOT to assess the shape of the terrain in quality assurance testing.
The mapping process also included collecting a variety of features in the I-94 corridor and surrounding side streets to a distance of 200 feet away from the highway right-of-way. Features mapped included:
- Guard rail
- Road signs, including those on side streets
- Mailboxes on side streets
- Guy wires
- Culverts with end treatments, with connectivity to provided subsurface drainage
- Drainage within the project area (provided by MDOT)
- Surface manifestations of utilities
- Trees, classified by size
- Driveways, classified by pavement type
- Parcel boundaries and tax IDs (from collateral data)
- Street names and addresses (from collateral data)
The combined aerial and ground approach proved to be very satisfactory for this complex and detailed engineering project. Every project has nuances that further expand our knowledge and abilities. This experience and all of our previous experiences allow us to successfully approach new projects and develop refined solutions using the latest technologies.
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Illinois Department of Transportation: Elgin O’Hare - West Bypass 
