[Xastir] painfully slow raster map performance

[Curt, WE7U]

On Fri, 11 Mar 2011, Kevin Ratcliff wrote:

> Now for my problem: raster maps seem painfully slow to zoom in/out and
> pan. This is on a laptop with a dual-core processor, 4GB RAM, and maps
> stored on an SSD drive. I'm not sure where the bottleneck is at, but
> it takes a long time to move around on the map.

Which raster maps?  USGS DRG's perhaps?


> Is the issue something that I've configured something incorrectly, or
> are raster maps in Xastir normally slow?

Depends on which types of maps you're using and perhaps the speed of your drive and drive interface.  Also of course memory and CPU.


> Is it a library that Xastir uses that causes the slowness, or code in
> Xastir itself?

If it's DRG maps, there's a lot of code going on in the background to warp the projection.

What you can do:  Set the zoom levels so that the 7.5' maps are loaded only at the levels where you need that detail.  Switch to the 1:100k maps above that, and the 1:250k maps above that.  With that scheme you can zoom in/out much more quickly 'cuz you've got fewer maps being loaded when you're zoomed out.

Another option:  Process the DRG maps into one contiguous map using GRASS or some other good GIS program, then break it up into smaller tiles in "unprojected" projection.  Create .geo files for each one and let Xastir have at that.  Xastir will treat it as any other raster in that case and tile them all together as you need, but it won't have to do all the math on it to get it into the right projection then.


> One idea I had for a workaround was to use postgresql+postgis with
> Xastir to put the positions into a database, and then load those
> positions into qgis for my raster mapping needs. The issue I ran into
> was I couldn't get the postgis stuff to work quite right because I'm a
> complete newbie to it, so I'm not sure if the problems I encountered
> were all my fault or just incomplete database support in Xastir.

Most likely incomplete support.  That's new-ish stuff and not complete yet.  One developer was working on it.

-- 
Curt, WE7U.        http://www.eskimo.com/~archer
Babysitting your tracker:  http://info.aprs.net/index.php?title=ControlOperator