Hi: While dealing with QMAPs and Google Satellite imaginery (through GDAL TMS support) I've come to a couple of possible feature improvements to QLGT excelent QMAP feature. This is somewhat related and can depend on Albrecht's proposal / investigation for GDAL error management.
First QMAP feature I miss, or don't understand correctly. To prevent wrong queries to Google servers (for non existant satellite imaginery ar certain zoom levels and above), I created a QMAP that for QLGT zoom levels 1 to 15 no map should be shown (empty file list for Detail Layer 1), and them, from zoom level 16 and above, Google Satelite imaginery (.xml file for GDAL for zoom levels 16 to 2048). What I'd expect is, at zoom levels below 16 (8, 4, 2, 1, as using "quadratic zoom"), no map, a scaled version of the map in the last zoom level with a defined map (zoom level 16) or just the inability to zoom in to zoom levels 15 and below. What I get when trying to go from level 16 to level 8 is zoom level 2048. I don't know if any of the alternatives I comment above is reasonable or even easy to implement, but cycling to the greatest zoom level is confusing. Maybe the problem is trying to limit the zoom levels for a map the way I'm trying to do it, and there is better way to do it. But would be a nice feature to have. Second feature / limitation I've come across while dealing with QMAPs. It seems there is 2^14 (16384) maximum zoom level in QLGT. For normal usage it is more than enough, but it can be a bit short for some uses. For example, with the Google Satellite XML definitin file I'm using , a zoom level x16384 spans an area the size of USA+Canada (1920x1200 screen resolution), but there could be use cases where this zoom level is not high enough. Don't know if this is worth the effort, or affects something else. Maybe is something that should be dealt from the map definition itself. Don't know. And third, related to Albrecht proposal for dealing with GDAL errors and the first feature I've commented on, maybe it's possible to detect typical 404 errors when downloading remote map tiles (don't know if GDAL reports error details so to make it possible to identify this kind of errors), and when some threshold if met, just refuse to further query the server at that zoom level or lower zoom level. And apply one fallback mechanism to show something on the screen, either the last correct zoom level, a scaled version of the previous zoom level, just a blank background with a notice showing the map server errors, etc. As you can see, nothing critical, and not even bugs in themselves, but could be worht some though about some or all of them. Greetings, -- Jose Luis Domingo Lopez Linux Registered User #189436 Linux Kubuntu 11.04 (Linux 2.6.38-8-generic-pae)
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