Hello everyone,
I’m using Google photorealistic and I’ve drawn an example polygon below. However, it does not show it like on Google Earth. Even though I changed the HeightReference values, there was no change in the cesium. How can I solve this situation, thank you in advanc
Polygon_3d.kml (1.7 KB)
Can you provide more information about what were the values the before and after the change? What change were you expecting to see?
I’m also going to move this to the CesiumJS category since it is more related to the viewer than the tiling and hosting of data.
I want the polygon to be as high as in the google earth screenshot, but it appears higher as in the sandcastle screenshot.
Hi there, it looks like your height values are defined in feet, not meters. You’ll need to convert them to meters. Here’s an example.
What do you think about Could it be possible that these heights are orthometric ? Because i am %100 sure the heights in meters. We found an information in blog mentioned Cesium working with ellipsoidal heights. Your sandcastle example looks fine but still need to be lower.
Yes, different height references could definitely be the source of the issue. As the article says, CesiumJS uses height above the ellipsoid.
I cannot confirm what height reference Google uses, but Mean Sea Level (MSL) would be plausible.
Is it possible to convert your heights from MSL to height above the ellipsoid to confirm?
google earth/kml spec uses the EGM96 geoid model. The elevation difference is going to be the geoid offset for that location ~ -35.3meters
When I converted the heights to ellipsoid it displayed correctly. Is there an easy way to do this?
Right now, the conversion will need to happen outside of CesiumJS.
As you mentioned, converting between reference systems varies by location. If we implemented this conversion in CesiumJS, we’d want to avoid bloating the library, so most likely we’d rely on an external API requests to perform the conversion.
We have support for MSL heights documented in KML Graphics Roadmap · Issue #2179 · CesiumGS/cesium · GitHub, and I’ll bump that thread with this use case.
