How to get terrain elevation at lat,lon in add-on?

[adamh128]

I am writing an add-on to draw mesh objects on the terrain surface, but I'm having trouble getting the terrain elevation at a given lat,lon.

I'm trying:

float elevation = (float)this._currentWorld.TerrainAccesso r.GetElevationAt(site.Latitude, site.Longitude);

This does return a value but when I use it to render the objects they don't sit on the surface, and they are all roughly at the same height. If they're at a position of a mountain, they appear inside the mountain.

I would be grateful for some help.

Thanks,
Adam.

[jp09]

Hi,

Funny, I aksed mashi the same question a few days ago !
Here's his answer on IRC chat :
<IGE-Jean> mashi : how can i get the height (dem height) at a given point (lat, lon) ?
<mashi> ok.. cool!
<mashi> you are building a layer with terrain?
<mashi> if so you can do QuadTileArgs.TerrainTileService.GetEleva tion... (something like that)
<IGE-Jean> ho ho, not so much. I'm just trying to do another modification to your landmark plugin
<IGE-Jean> Just to avoid having to set absolute altitude, replacing it with relative altitude (relative to the ground)
<IGE-Jean> But i'd love to uild a layer with terrain
<IGE-Jean> Until now, i just managed to do it tiling my data, and re-using the earth.xml and image.xml files
<mashi> oh.. because then you don't have terrain readily available, you have to find a layer that has terrain (in the renderableobjects tree) or create a new TerrainTileService()
<IGE-Jean> Oh. So, i believe i'm really lost.... (
<IGE-Jean> Until now, i didn't really understand what we can access from the plugins, and how...
<IGE-Jean> But maybe you could tell me ? ;o))
<mashi> fill in the blanks here: http://www.worldwindcentral.com/wiki/Plugin_FAQ
<IGE-Jean> You mean, I fill the question, and YOU fill the answers ? ;o)
<IGE-Jean> mashi : please, how to browse the renderableobjects tree ? I'd like to use the SRTM terrain. Looked for, but i'm really lost...
<mashi> IGE-Jean: ParentApplication.WorldWindow.CurrentWor ld.ChildObjects



I hadn't much time to work on it since he answered me, so I can't help you much further. But if you find the way, please, just tell me ?

[adamh128]

I have pretty much got it working but it's not completely accurate, if you can refine it to get it working better, please let me know...

float elevation = (float)this._masterLayer.WorldWindow.Cur rentWorld.TerrainAccessor.GetElevationAt (_latitude, _longitude, 100.0 / this._masterLayer.WorldWindow.DrawArgs.W orldCamera.ViewRange.Degrees) * World.Settings.VerticalExaggeration;

[Dave0]

I noticed that if you try using GetElevationData(...) without specifying the third paramter, the wrong elevation can be returned. This could be where the accuracy problem is, although I am not sure what a better third parameter would be.