Elevations

[Pipeliner_USA]

So I have 111 pictures I flew of a lot using Drone Deploy. I can't seem to obtain the deliverable I am looking for, which is a site plan showing ground elevations...ideally contours. Each photo is backed by EXIF data as far as I know, with the XYZ of each snapshot. Not a huge lot. I just can't seem to get a program to show the XYZ properly though, no matter how careful I am that the coordinate systems are aligned. For instance, Civil3D point cloud upload (from the DD .las file) has the XY ok but the Z is all out of whack. The DD elevation exports are arbitrarily based it seems and my elevations are in the -9 to 20 range... meters? Just confused. Looking for a solution that makes sense.

 

[Bigriver]

Yep, using P4D my elevations after initial processing are also pretty crazy. They may be hundreds of feet off my datum. Don't know why, and it may be because I am doing something wrong.

But since I am shooting for near survey grade orthos, setting GCP's is part of my process. And after reprocessing with the GCP's, my results are locked down to the project datum, and the accuracy can be proven to myself and the client with a few check points.

 

[doktorinjh]

@Pipeliner_USA , your elevations are based on a consumer grade GPS unit that sits in the DJI, it's really not that good so you can wind up hundreds of feet of error. Your horizontal error can be 10s of feet, too, depending on what you're comparing it to. As @Bigriver mentioned, you need to incorporate ground control and aerial targets into your survey to get something reasonable. The GPS heights are based on orthometric height and your existing data is probably in ellipsoidal height, etc., so you've got to get them talking the same language.

 

[Pipeliner_USA]

Thanks for the replies. So I’m a land surveyor as well and this project I have tied into a vertical benchmark, and painted some big X marks for GCPs. But those X and Y are still arbitrary. Am I out of luck?

 

[doktorinjh]

painted some big X marks for GCPs

I don't really use Drone Deploy, but I assume there is someplace in the software to mark your GCPs and provide the location data? The program should use those as the definitive elevation constraint, but it sounds like it's not doing that.

 

[Pipeliner_USA]

I don't really use Drone Deploy, but I assume there is someplace in the software to mark your GCPs and provide the location data? The program should use those as the definitive elevation constraint, but it sounds like it's not doing that.

There is a place to enter GCPs, but what im saying in... i don't have them on an official coordinate system. i just have official vertical control. i surveyed the property with my total station and then tied it into a benchmark nearby. But my XY (N,E) values are still arbitrary. So i don;t know if i can even utilize the GCPs