Global Terrrain projection problem

[carlos.lozano]

We generate an ObjectGlobalTerrain with images in UTM projection, and we have compared it with an ObjectTerrain generated with the same images and it's different because it's slight rotated.

Another test was to generate ObjectGlobalTerrain with images in UTM and Geographic projections and the final result is the same (source images projection don't affect final result).

 

This rotation is a problem because we want to convert geodesic coordinates to local cartesian coordinates and place out 3D objects in the right place given longitude and lattitude.

 

In the FTP we have included 3 screenshots , a ObjectGlobalTerrain with UTM imagery, a ObjectGlobalTerrain with Geographic imagery and finally a ObjectTerrain with UTM imagery. If you use a photo edition software with layers, for example Adobe photoshop, and overlap the images, you can see the slight rotation in the ObjectGlobalTerrain with respect to the ObjectTerrain.

In the video the static terrain is the ObjectGlobalTerrain and the one that is being moved is the ObjectTerrain, as you can see, there is a slight rotation with respect to the ObjectGlobalTerrain.

 

In the FTP file "global_terrain_problem_projection.7z" we have also included two textures so you can do tests, one in UTM projection and the other in Geographic projection.

 

Thanks

We have a problem in generating the global terrain, we have used images with both UTM projection and Geographic projection, and both look exactly the same. But when generating them with the normal terrain in UTM projection, we realize that the global terrain appears rotated.

[maxi]

Hi Carlo,

 

Your ObjectTerrain (old one) with utm projection is created "as is" in a utm zoned projection, i.e no transformation applied. While ObjectTerrainGlobal generate data transformed to geographic projection.

This caused a mismatch, the same as if you transform utm to geographic projection source, it will be rotated (For example with gdal tools: gdalwarp -t_src "proj=longlat +datum=WGS84" source_name dest_name).

 

Basically to match old and new terrain, you need to generate old one with sources in geographic projection. Than new terrain will match it, no matter what projection will be used.

[ivan.cuevas]

HI maxi,

Thanks for the answer.

So Landscape Tool generates a ObjectTerrainGlobal with geographic projection.

 

Is there actually in Unigine any function or class to transform from 3D point to geographic and viceversa?

It's something similar to what DatasetRasterPosResolver does with images.

[maxi]

Yes, please look at GeodeticPivot class, it has mapGeodeticToFlat and mapFlatToGeodetic methods.

[ivan.cuevas]

Testing the geodetic pivot we faced two problems:

 - GlobalTerrain in a GeodeticPivot freezes the application when you are flying over (testing a terrain 50Km x 50Km works ok, but generating a 100Km x 100Km  freezes the navigation for 2 secods more or less).

 - Trying to move our alreday created terrain to GeodeticPivot, freezes Unigine Editor completely, making this operation impossible.

 

Thanks.