AFAIK, all the web tile services are Mercator. The issue here is finding a way to make the web tile services render quickly. My hunch was that vector overlays would be less computationally expensive to reproject, so leaving the tiles in Mercator would be most efficient. >, I occasionally use USGS DRG GeoTIFFs, but I prefer the scanned topo tiles. The DRGs don’t look as nice because they’re limited to ~5 colors (or something like that), not millions of colors, meaning there’s no antialiasing on the text and contour lines. This makes a big difference in readability, at least for me. Where would be a good place to improve efficiency? My two ideas so far: 1. Have Xastir reproject each tile before caching it (rather than caching the original download), so they do not need to be reprojected on each cache read. I don’t know if this idea is compatible with how Xastir stitches tiles for display. 2. Add a ‘fixed zoom Mercator’ mode to Xastir where tiles are displayed in their native size/shape and everything else gets reprojected. This sounds really difficult to implement :-) Tom KD7LXL Source.