fixed disappering tiles on zoom 1-3

[nextfullstorm]

Tile bounds calculated BaseProjection::CalculateGeogBounds can overlap projection limits, causing GDAL error and tile disappearing. Take world map for example: we have tile grid 4*4 on zoom level 2, tile height (lat) will be ~18, 66, 66, 18. But for lower tile row BaseProjection returns top lat -66 and height 66, which causes to transform via OGRCoordinateTransformation::transform latitudes like -133 (-66 - 66, top lat - height) and GDAL error. I'm not able to understand, why this doesn't happens with top tiles row (why BaseProjection calculates right height 18 for them), but able to patch it around overriding BaseProjection::CalculateGeogBounds in MercatorProjection::CalculateGeogBounds and checking calculated tile bounds against min/max lat/lon.

That's vanilla MapWindow:

Again, with fix:

[ultraTCS]

Hi, is this issue perhaps the same as this?
https://mapwindow.discourse.group/t/shapefile-polygon-fill/254?u=ultralt

thanks.

[nextfullstorm]

Hi, is this issue perhaps the same as this?
As far as I can tell, no, it isn't. This bug is about wrong tile bound box calculation. Do you have "GDAL FAILURE: latitude or longitude exceed limits" message when you changing zoom level?

[ultraTCS]

No. Do not get that GDAL error. There is no error message at all in this scenario.
Thanks for your response.

[jerryfaust]

Assigned to MWGIS-208.