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Relative and absolute accuracy

Posted by Russell on February 26, 2013 at 5:55am

hi i am looking at using a UAS to do some aerial photography with the view to producing a DEM model from photogrammetry, i have been doing some research but did not find exactly what i want, can anyone help answer the following questions

1 what accuracy can you get from photogrammetry with a UAS in relation to X Y&Z and how does this compare to different flight levels

2 what is the best Photogrammetry software to use or the most economical as cost is always a factor

3 what is the best or most economical UAS to use

thanks

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  • JP February 26, 2013 at 2:12pm

    Hi -- here are a few suggestions:

    1: Here are the absolute accuracy you can expect using on-board camera GPS, flight controller GPS and also GCP. This example is around 3.4 km sq. "The Pinery Project" .. Of course you can obtain even tighter results over a smaller area of with additional (well placed) GCP. 

    The relative accuracy inside the DEM is great and improves slightly with the use of GCP. If you don't need cm or submeter precision you can get away without GCP.

    This was flown at 200m with a 12 mega pixel Canon SX260HS running CHDK alpha. GSD was 6.7 cm per pixel. Focal Length was 4.5 mm. 

    Values below represent absolute accuracy for this data set.

    Test Case RMSE X (m) RMSE Y (m) RMSE Z (m) CE90 (m)
    1 - Camera Tags 8.4 6.7 27.6 14
    2 - Falcon Tags 4.5 9.2 27.7 6.4
    3 - 6 GCP 0.17 0.18 1.9 0.35

    Same data set with an additional 3 GCP:

    Pinery_UpdateGCP_chart.JPG

    2: Have a look at Pix4D, Inpho.de/Trimble, Photoscan or DroneMapper. I can only speak for DroneMapper, we charge $20 per km sq for processing to the highest GSD available with your imagery.

    3: If you are looking to build DEMs for smaller areas, you can't go wrong with a DIYDRONES copter. For larger areas, like the Pinery we suggest a platform that is very stable and has great duration. The two that come to mind are Falcon UAV and Pteryx. 

    Good luck!

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