topic locationToElevation in Qt Maps SDK Questions

locationToElevation

HidekiShibata — Wed, 31 Jan 2018 23:43:38 GMT

Hi,

I am using Surface::locationToElevation function.

1) It looks locationToElevation returns nearest neighbor result. Is there any way to get bilinear interpolated elevation?

2) When I attached ArcGISTiledElevationSource to the surface, locationToElevation returns nearest neighbor result.

But if I attached (only) RasterElevationSource to the surface, locationToElevation returns flat data.

I checked that RasterElevationSource configuration worked fine displaying 3D map image.

Is this right behavior?

Regards,

Hideki

Re: locationToElevation

LucasDanzinger — Mon, 19 Mar 2018 13:28:41 GMT

There is currently no way to force bilinear interpolation for locationToElevation.

As for the raster issue, that does not sound correct. Are you saying your raster has elevation data but it displays flat?

Re: locationToElevation

HidekiShibata — Mon, 19 Mar 2018 17:41:04 GMT

Hi Lucas,

In my application, I am using 2D map display only.

When user select two points on the map, I tried to get elevation between point1 and point2 every 1m to make cross-section data.

Result does not have smooth elevation change, it was step elevation change, looks like Minecraft world.

I understand elevation sources are 10m-100m mesh depend on the location. United States looks less than 10m, Japan looks 30m resolution.

I can not get this mesh resolution information from locationToElevation, so I can not interpolate the result by myself.

I tried to make simple 3D application to test, the terrain display was fine.

I believe your code generate mesh vertices at DEM cell's coordinates, so OpenGL automatically interpolate between cells.

I checked both my local raster DEM and your elevation server. Both 3D display looks fine, but locationToElevation results were not smooth.

I would like to ask you to change locationToElevation() returns bi-liner interpolated elevation using 4 nearest cells instead of just return nearest neighbor cell's elevation.

Or, if locationToElevation also returns nearest neighbours horizontal coordinates, I can do bi-liner interpolation by myself.

Regards,

Hideki

Re: locationToElevation

LucasDanzinger — Tue, 27 Mar 2018 15:43:45 GMT

Thanks for the explanation. I'll pass your request on, but if you can log a support request with Esri Support or your distributor (if non-US), that would be the official way to submit an enhancement request.