heightReference for position in CZML

CesiumJS
1

Hi all,
I have converted a GPX track to CZML. I have the path rendering properly but am unable to get the path to clamp to ground--it's roughly 30m below the surface but varying over time--probably because the GPS was changing its height fix over time. I attempted to resolve this by scrubbing the heights through a sampleTerrain function, which resulted in slightly different values, but still roughly 30m below the surface.

Is there a way to tell a position -> cartographicDegrees to clamp itself to the terrain?

Thanks,
Ben

2

Hi Ben,

I think you can use the CZML property HeighReference with the value
CLAMP_TO_GROUND

``

Thanks,

Gabby

3

Thanks for the suggestion. I've given that a shot. Appears to have no effect.

"position": {
    "interpolationAlgorithm": "LAGRANGE",
    "interpolationDegree": 1,
    "epoch": "2017-06-05T16:49:14Z",
    "heightReference" : "CLAMP_TO_GROUND",
    "cartographicDegrees": [
      0,
      -106.957785124,
      31.9563742261,
      1218.13,

4

Sorry I don’t have a czml example, but here’s the sandcastle demo for clamping to ground: http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Ground%20Clamping.html&label=Showcases, maybe the “Sample line positions” example is relevant?

5

Thank you for this help. My code to reset the heights of the path points wasn't using sampleTerrainMostDetailed. Now it is, and it's working like a charm. I really appreciate the help.

6

Great! I’m glad to hear its working!