Comment corriger l'altitude de mes cartes 3D drone2map ?

Question

<\/HEAD>Comment corriger l'altitude de mes cartes 3D drone2map ? J'ai quelques ensembles d'images qui ne disposent pas de points de contrôle au sol. Les cartes 3D finissent par être décalées vers le haut ou vers le bas en fonction de mon lieu de décollage. J'ai trouvé le paramètre "Image Altitude" sous "Flight Data", mais après avoir modifié "Adjust Using", "Constant Elevation", "Takeoff Elevation" de 2 mètres, cela ne change que l'altitude des points et ne semble pas modifier le niveau de la carte. Dois-je retraiter le projet ou changer quelque chose dans ces paramètres pour appliquer cette modification ? <\/P><\/BODY><\/HTML>

ChrisDembinsky · Answer

Sorry I did let this question bleed a bit. My main problem at this point is just to get a 3D mesh DTM to look right on the Esri base map. Could I use the road as a control point so that it matched with the base map? I know it hasn't changed.

Comparing two 3D maps was a related though and yes, I have before and after flight using the same mission. So the maps look similar but the elevation near the water, and the foot of the dune, changed a bit. It's not important to me at this point to make a measurement.

Cody Benkelman · Answer

Chris

thanks, this helps understand the context - however I'm concerned about trying to advise you with an ad-hoc workaround that may ultimately lead to bad results.

If you're trying to measure volumes of sand on a beach, accurate data products in (x,y,z) will be critical - and my advice is "this is impossible without high quality GPS for ground control".  Further, you said "sand loss" which implies you have a "before" dataset - either from a prior drone flight or perhaps lidar?  I don't believe you can hope to compare two datasets without high accuracy control points, and ideally use the same control for "before" and "after" or if the earlier dataset is lidar, perhaps you can use that for control (although I'm thinking it would only be usable along the road where you have hard structures, and if your control is limited to one side of a project, the other side can still drift up/down leading to measurement errors).

Do you have a professional surveyor you can include in the project for advice?

Cody B.

ChrisDembinsky · Answer

For the most part I'm working with a 3D mesh and 3D DTM but in some of my projects, I would like to do measurements of sand loss so I may need to use one of the other options.

So in most cases, I don't think I need precise Z alignment. It would be nice if there was a way to determine the elevation of the base map in a given location. Then I could use that elevation as my offset/control point. I take off from the street so that's easy to pick out of the map. right now I'm just going off the trial and error strategy but it's not a reasonable method. I wish I had the ability to implement control points but I didn't for all of my projects so far. Apparently, I also don't know how to share the 3D DTM but here is what I could share: https://volusiacountyfl.maps.arcgis.com/home/webmap/viewer.html?webmap=62418d8d0e954968bdade8230f3c1ad8