On Fri, Sep 07, 2012 at 10:07:14AM -0600, we recorded a bogon-computron collision of the <[email protected]> flavor, containing: > Why is Xastir slow to render raster maps? I'm curious what is actually > happening behind the scenes. It appears that Xastir is re-projecting > the raster maps, requiring an expensive render.
Yes, that's what's happening. > Why not just > re-project the APRS stations and any shapefile overlay to match the > raster tiles? Wouldn't this be much faster? Yes, it would, but then you'd have to deal with the issue that many rasters aren't in the same projection, and the vector overlays are often in something else, too. So the approach is that the Xastir coordinate system is basically Platte Carre (equidistant cylindrical) with a scaling so that the entire globe is represented by long integer coordinates. Everything is done in that coordinate system, and maps have to be reprojected. > I normally use Xastir with a USGS topo tiles base layer (from ESRI, > using the OSM tile loader) with an OSM Cloudmade shapefile overlay. If you really want topo maps as a base layer, you're better off getting USGS GeoTIFFs and doing the reprojection once, converting them to WGS84 lat/lon instead of NAD83 or NAD27 UTM. This way, no projection is done at render time. You can do the reprojecting using gdalwarp. -- Tom Russo KM5VY SAR502 DM64ux http://www.swcp.com/~russo/ Tijeras, NM QRPL#1592 K2#398 SOC#236 http://kevan.org/brain.cgi?DDTNM "And, isn't sanity really just a one-trick pony anyway? I mean all you get is one trick, rational thinking, but when you're good and crazy, oooh, oooh, oooh, the sky is the limit!" --- The Tick _______________________________________________ Xastir mailing list [email protected] http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
