Using drones to capture high resolution systematic images to process highly accurate and detailed aerial maps is benefiting land surveyors and end users throughout the country. This project was completed for a land surveyor on an apartment complex here in the Dallas area. The property owners were refinancing the property requiring an updated survey of the property.
Deploying a DJI Matrice 200, we captured hundreds of 21 megapixel images at an altitude of 100’ with a side and front lap of 80%. For this particular project, following this guideline allowed us to process a map in the highest possible resolution, 0.36″/ pixel. Each image has gps meta data that are critical to process an accurate map.
In order to ensure a certain level of accuracy is delivered, you must either capture ground control points to incorporate in to the processes aerial map or capture your images with an RTK system. Otherwise, the image data captured will not be precise enough on its own to process a map that consistently offers 1 foot or less of true ground level accuracy. Many projects we work on require a 3-5 cm level of accuracy.
Achieving Highly Accurate Maps
We captured 12 ground control points throughout the site and used 8 of them to process the map. The points were captured on the WAD27 North Texas Central (EPSG 2276) coordinate system.
Because of the process we used, we were able to achieve a ground sampling data (GSD) of 0.3 in/pixel, an approximate horizontal relative accuracy range of 0.7 in, an approximate vertical relative accuracy range of 1.22 in, optimized camera location error of X 0.52 in, Y 0.48 in, Z 1.22 in, and an optimized camera location XYZ RMSE 1.41 cm/pixel.
Although the highest resolution map, at .36”/ pixel, was not actually used on the project, we were able to get an impressive resolution export. Due to the size of this high resolution images, surveyors often request either 2” or 4” of resolution as the size is more manageable for the programs they use.
The land surveyor we worked with used this to quickly count parking spaces, verify building corners and locations, visually verify and locate water cut offs, man holes, power poles and other objects that are time consuming to document in the field. While this project did cost money, the amount of time and man hours saved in the field ended up saving the surveyor and end client money due to the efficiency this service was able to provide.
Aerial mapping is just one of the many services UAV’s bring value to. To learn more about how drones can benefit your business, give us a call at (214) 842-6000.