Mississippi Bluff Project

Faced with the task of redesigning the surface and storm sever drainage on a steep, inaccessible Mississippi bluff, the region's City Engineer turned to AeroView Services to provide the topographic mapping and drainage analysis.

 

Utilizing AeroView Services and its UAV aerial mapping would serve to decrease both project lead time and cost, but the biggest concern was safety as the steep bluff was completely tree/brush covered. Its heavy surface erosion also precluded the use of years old statewide LIDAR data. In addition, they needed survey information on the above-ground storm drain coming from a nearby decades-old housing development. The drain was installed along the surface of the bluff and was failing to the point of pushing manhold lids off.

 

The picture on the right shows the unedited point cloud of the site. Note the heavy amount of trees and vegetation on the site, especially the bluff.

With the right conditions, UAV mapping provides a good bare earth surface from data collected, even through dense tree cover and vegetation. On this particular project, we flew the site while there were no leaves on the trees and shrubs, allowing sufficient exposure on the ground. We then used photogrammetry to process the point cloud and surface.

Using the point cloud as our primary data set, the next step was to remove any non-ground points, thus leaving a point cloud that represented the bare earth of the site (see below).

Even after an aggressive cleaning of the raw point cloud, we are still left with over 10,000,000 points of data, each associated with a X,Y,Z coordinate (northing, easting, and elevation).

This bare earth point cloud allowed us to create a 3D surface, representing the surface of the site, that can be easily loaded into any CAD software and used as the basis for the drainage analysis and design (see below). Across the site, the accuracy of the surface was 0.06' horizontally and 0.1' vertically.

In addition to the 3D CAD surface, we also created a high resolution orthophoto, which is made by stitching photos together and geometrically modifying them and removing perspective, thus allowing accurate measurements to be taken from the photo.

Additionally, the orthophoto can be imported into CAD software and used to identify small features on the site, such as curbs, inlets, etc. (see left photo).

Together with the 3D surface and orthophoto, we also supplied a contour map with 1' intervals (see photo right)

Surveying the Mississippi Bluff Project the traditional way would definitely have presented a sizable safety risk. Using UAVs not only provided the needed safety benefits, but there was also a significant cost and time savings for the client. 

For more information about this project or to learn more on how AeroView Services and UAVs can benefit your company, please contact us now.

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