max zoom selection uses unconverted source units

[dnomadb]

The source's resolution is converted to meters here:

mapnik-omnivore/lib/raster.js

Line 162 in 29ead36

var pixelSize = utils.convertToMeters(this.details.pixelSize, utils.getUnitType(this.projection));

But then the resolution in native units is then used to calculate the max zoom:

mapnik-omnivore/lib/raster.js

Line 173 in 29ead36

var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, _this.details.pixelSize[0], thresholdWeight);

This results in incorrect maxzoom selection for non-meter source data, as the thresholds for zoom levels are defined in mercator meters. This can be fixed by simply swapping out _this.details.pixelSize[0] for pixelSize[0] above.

cc @pratikyadav