AGL Sweet Spot for 3D Survey Mapping

Is there a Sweet Spot for the AGL?

I have mapped thousands of acres over the past 5 years and have determined what I have been using for the best Above Ground Level (AGL). This test is to quantify my experience.

Hypothesis: To determine if there is a difference in 3D accruacy depending on the AGL above the area being flown.

Testing site: A 5 acre rectangular parcel that contains brush, trees, buildings and paved streets.

Drone Platforms: Inspire 2 with X7 camera, 16mm lens

AGL: 100', 150', 175', 200', 225', 250' & 300'

Overlap: Front 70%, Side 70%

For more details on the drone flight parameters see book "Flight Parameters" at www.cc4w.net.

Processing software: Metashape Pro by Agisoft

For more details on using Metashape Pro for 3D mapping, see books "Metashape" and "3D Road Intersection" at www.cc4w.net.

Five (5) GCPs were placed in specific locations on the 5 acre test site. One near each corner and one in the middle. Multiple checkpoints were scattered around the site.

For more detailed information on the NA, review books "What's My Mission?" and "Time to Fly" at www.cc4w.net.

The test site was flown with the Inspire 2, X7 camera/16mm lens.

The following chart reflects the RMSEz values for multiple checkpoints scattered throughout the site over a range of 100' to 300' AGLs.

As can be seen in the above charts, the Sweet Spot for the X7 is 200' AGL.

The Revised column shows only the RMSEz values below 0.20'. None of the checkpoints RSMEz values for the 200' AGL were above 0.05'.

The 250' AGL values were not utilized due to poor image quality. I failed to focus the camera properly. I did not want to fly the site again due to the travel time needed from my home base. I will fly it again at some point in time.

The online "Flight Parameter" web app shows the values for this drone platform at 200' AGL.

Conclusion

Using a minimum of 5 GCPs for sites under 25 acres and the formula of (Acres * 0.2 = # of GCPs) for above 25 acres works out very well for the X7 camera/16mm lens at 200' AGL.

200' AGL is the Sweet Spot for the Inspire 2 X7 with 16mm lens.

For the Mavic 2 Pro the Sweet Spot is 150' AGL using the formula of 5 GCPs for sites under 17 acres and the formula of (Acres * 0.3 = # of GCPs). I will be verifing that in the distance future.

It is clear from this test result that flying higher or lower does not give better results. The combination of the drone platform, AGL and GCP configuration will produce the best results.

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There are two training videos available on "3D Mapping" located at https://vimeo.com/ondemand/smms/

www.cc4w.net

"I fly Drones for a living mapping the earth one (1) acre at a time and write DIY surveying math/mapping books/videos for fun!"

Check out the New video series on "Survey Mapping Made Simple".

https://vimeo.com/ondemand/smms/

Sponsored by Cooper Aerial

Leaders in Modern Mapping Methodologies.

Cooper Aerial

A Free online "Flight Parameter" web app for multiple drone platforms is now available:

Click here to open.

If you like the information provided above and would like to see more in future email posts, then consider purchasing some of my books and videos to help support the effort. As all of you know, computer hardware, software and drones costs money. I put 100% of my book/video sales back into the business to write more books, produce videos, buy drones to test and so forth.

Thank you all that have supported this effort. It is greatly appreciated.

www.cc4w.net

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