Calculate elevation angle as observed from the ground

[Fidel Perez-Smith]

Hi,

I have two points consisting of long/lat/height. I'd like to calculate the elevation angle (as though we were standing on the ground at the 1st point looking up at the 2nd point)

I've been working on this gist: http://cesiumjs.org/Cesium/Apps/Sandcastle/?src=Hello%20World.html&label=Showcases&gist=64912dc9178bf064ade2f65f671bfa56

Ultimately I'm trying to adjust the pitch of the cone to match that of the blue line.

Any help would be greatly appreciated.

Thank you,

Fidel

[Fidel Perez-Smith]

Kevin Ring suggested the following. Could someone please walk me through how this would be done in code?

If you're interested in the elevation angle as observed by a point on the ground, your plane of interest is probably the local horizontal plane. In other words, a plane with a normal parallel to the WGS84 ellipsoid surface normal. This plane isn't exactly the same as what a level would show you at that point on the Earth, but it's very close. To transform your target point in the Earth-fixed frame to this local horizontal plane, you can use Transforms.eastNorthUpToFixedFrame. That returns a Matrix4, which you then multiply your target point vector by, yielding a new vector. Normalize that vector, and then the elevation angle is simply asin(z) of the normalized vector.

[Rachel Hwang]

Hi Fidel,

I used a slightly different method, but try this code example: http://cesiumjs.org/Cesium/Apps/Sandcastle/?src=Hello%20World.html&label=Showcases&gist=c16fff23b7b1283afea477747c731e37

Best,

- Rachel

[Fidel Perez-Smith]

Wow, that is perfect. Thanks Rachel