Maps elevation wrong?

I rendered a maps through Drone Deploy map processor (and fly with drone deploy android apps)
http://drdp.ly/LloeDr
but the elevation is off by a lot (the whole maps looks like a giant sphere while it’s a level field). I have no idea why since I process this data with altizure and have very good result. Any idea how does this happen and how do I get better result?

hello? anyone? any idea will be appreciated

hi @Minh_Nguyen

Apologies for the delay in response.

There are a couple things going on here

-Each of the images has a very large blur in the center. This looks like glare from the sun. I’d recommend a) trying to fly at a different time of day or b) going with the “sunny” settings in DJI GO rather than the auto settings in our app. if you do the latter, you will need to disable the automatic settings in our app.

-The secondary issue is that mapping areas where the elevation does not differ much is a particularly complex issue for photogrammetry- the cameras have trouble reconciling small depth differences from a high altitude. Some suggestions are here:

Best Practices to Fly and Stitch Crops

thanks,

I also am having trouble with elevation. When I place a location and get the GPS the elevation is wrong. I put it at the drone’s home point and it shows 17 ft. Not sure why, but I need to figure it out soon…trying to sell my boss on this software…I work for an excavation company and elevation is everything.

Please help

Is that 17 ft above sea-level? What is the actual elevation of the home point?

The elevations given by a Location in Measurement Annotations are never close in all my maps. This is because they are based upon the barometer in my Phantom 4 Pro drone. To fix this you can use Ground Control Points (GCPs) but this has some expense, it laying them out and it map processing cost and the type of Plan you need. Eventually DroneDeploy will have a Zero-Set option so you can adjust the baseline of all your elevation measurements. I fix this issue another way using an Auto-Calibration Technique (ACT) but this requires changing the Exif data in all the photos. Most pilots probably are not interested in doing this but if you want details you can look in: Steep Terrain Question on the Forum.

That being said, the relative accuracy of Barometer-based elevation values can be quite good. Is the elevation difference between the home point and other points you measure reasonable? If so, then you just need to calibrate the elevation baseline: GCP’s, ACT, or, the future option, of Zero-Set in DroneDeploy.

The reason many drones use a Barometer for relative altitude measurement is that GPS altitude accuracy is very bad, 8 meters or so, and would cause large errors in elevations values. The Barometer has about 1/40th as much error so it is a better choice but its zero point must be calibrated. Barometer-based altimeters have been used to fly maned aircraft for over 100 years because of their good relative accuracy. But every pilot knows to calibrate the altimeter to read zero for their current elevation before takeoff. Somehow this learning is not yet being applied routinely to DroneDeploy missions and maps. I certainly apply it to all my maps and I am very happy with both their relative elevation accuracy and absolute elevation accuracy.

In the future, GPS altitude data in an affordable drone may improve to the point it is better than a Barometer. This is possible today with an RTK-equipped drone but the cost is much higher (typically > $10K). But you need to be careful when evaluatingt RTK drones as they may NOT be logging the RTK corrected GPS altitude to the photos (currently the case for the new DJI Matrice 210 RTK drone).

Regards,
Terry.

Hi @mrkmrtn,

To add onto what @SolarBarn has shared, I suggest taking a look at our How Accurate is My Map? support page.

Cheers,
Christina