Very High Accuracy Mapping - Continental Mapping Consultants

Very High Accuracy Mapping using Helicopter and Fixed Wing Platforms

To support our engineering clients with very high accuracy mapping needs, Continental Mapping has developed specialized photogrammetric techniques utilizing imagery captured at low altitudes from helicopter and fixed wing platforms.
These unique acquisition techniques, coupled with precision airborne GPS (ABGPS), provide solutions that yield vertical mapping accuracies of 0.1 feet or better.

Railroad Corridor
This high resolution image, acquired using a helicopter, is detailed enough to read street signs. Patrick Engineering recently engaged Continental Mapping to perform aerial mapping along 13 miles of a busy railroad corridor in the south suburbs of Chicago, Illinois. Using stereo imagery captured by a low-flying fixed wing aircraft and ground control survey set by Patrick Engineering land surveyors, Continental Mapping's photogrammetrists were able to map features along the corridor with vertical accuracies of +/- 0.1 feet on hard surfaces. Patrick Engineering Project Manager Scott Lutz stated that "the mapping requirements were to obtain surface terrain information that would near the accuracy of having a survey field crew perform the work themselves. However, due to the extents of the project and the complications of accessibility, it was more cost effective to have this acquired with aerial mapping."

Patrick Engineering saw several other benefits to Continental Mapping's aerial mapping solution. The mapping limits were extended to 25 feet beyond the corridor's boundaries to aid in the design process by letting Patrick Engineering see what was the next to the project area. A 3-inch resolution orthophoto was delivered to assist the engineers in identifying the types of signs, signals, and electric boxes along the corridor. Additionally, 3D graphical triangles representing the DTM model were delivered to Patrick and were then converted into a TIN model for use in GEOPAK software. The engineers used GEOPAK to create alignments of the rail as well as cross sections for design purposes.

Interstate Corridor
Continental Mapping also recently provided very high accuracy mapping services in support of interstate design work. For an engineering firm specializing in transportation design, Continental Mapping had four line miles of existing interstate corridor flown by a helicopter equipped with a mapping camera. Using photogrammetric methods, mapping at a 1"=10' scale with a vertical accuracy of =/- 0.05' was delivered. In addition to aiding in design, the mapping is being used to calculate the volume of road surface materials that need to be removed and for estimating the amount of materials needed to replace the road surface, just one of the many novel applications to which such detailed mapping can be applied.

For yet another transportation engineering client, 55 line miles of a proposed interstate corridor were mapped using imagery taken from a fixed wing aircraft. In areas with hard surfaces, +/- 0.1' accuracies were verifiably achieved. Compiled from more than 1,800 frames, planimetric mapping at a 1"=20' scale and 3" pixel resolution orthophotos were delivered to the client in addition to the topographic DTM. This project was completed in less than three months.