WMS mapalgebra layer’s rendering crashes for layer in other SRS than WebMercator

[micpilon]

I am having issues related to serving mapalgebra computed layers such as hillshade, slope and aspect with a WMS when the source layer has a spatial reference system different than WebMercator.
Browser throws: Layer (hrdtm-hillshade) not found or CRS (EPSG:3857) not supported
Console throws: ERROR geotrellis.server.ogc.wms.WmsView - java.lang.RuntimeException: Tile is too small to get surface values. (1, 1)
Here's a more detailed stack trace

The source layer behind the mapalgebra computation (type = "rastersourceconf") does render correctly. Also, the WCS displays these mapalgebra layers correctly spatially in a GIS, which leads to think that this is mostly a rendering problem.

I can provide you with samples soon.

Thanks!

[pomadchin]

Hi @micpilon! Thanks for catching that; the example would be very useful indeed

[pomadchin]

A small update: the layer read is for some reason empty. There is a bug in GeoTrellisRasterSources that could stitch an empty query result into a large raster (see locationtech/geotrellis#3240) which caused a bit unreadble error messages.
In general it looks like the ingested layer is empty. Its metadata (bounds / extent / crs) can be incorrect.

[pomadchin]

It looks like the problem is in the zFactor set for the hillshade operation. Try to set it to smth like 9.166226027378224E-5 or 1.254307051800487E-4 for this dataset

[pomadchin]

The issue was that the histogram used the min cellSize available for the layer, and such cellSize could be too small to calculate the hillshade.

This PR #261 should fix it: it tries to select the still the minCellSize but it selects the layer that has enough of pixels to compute the histogram.

[micpilon]

PR #261 indeed fixes the problem. Thanks @pomadchin !

[pomadchin]

@micpilon thanks for reviewing it! closing!