csv-geo-au points incorrectly located in 3D Terrain view

[tobybellwood]

Using csv data from https://www.data.act.gov.au/api/views/nuki-h32w/rows.csv?accessType=DOWNLOAD

Looking at http://staging.nationalmap.nicta.com.au/#share=s-85BZLceJMeKfhTkzazIXV41tRag

and paying attention to the crashes on the corner of Eastern Valley Way and College St for reference - they appear correct in 2D and 3D Smooth, but are misplaced in 3D terrain

Any ideas why?

[meh9]

This is because points are always placed on the ellipsoid (i.e. sea level), so when terrain is turned on they suffer from parallax.

See #702

Looks like the Cesium feature to fix this is still open: CesiumGS/cesium#2172

But maybe we can solve this at least for points using some hack, @kring?

[geoffrowland]

Looking forward to visualising vector data on terrain, too ;-)

[kring]

It's possible to fix this by sampling the terrain under every point and adjusting its height accordingly. We have to be careful this doesn't lead to very long load times for some CSVs.

[kring]

Cesium does have support now for points / billboard on terrain, so we may be able to just enable it (but again be careful of the costs).