[Xastir] RasterMaps and Xastir

[Curt Mills, WE7U]

On Mon, 7 Apr 2003, Pascal Levasseur wrote:

> I am running Xastir 1.10 compiled from source on Debian 3.0 on a 400
> BogoMips 64 Mb computer and the vector maps display ok.

Xastir 1.1 is _very_ old (over a year).  You should at least upgrade
to one of the 1.1.4 snapshots, the latest of which is dated April 1,
2003 (they come out about every two weeks).  Even better yet is to
run the CVS version so that you can keep up with the latest
features.


> But I have few issues with raster maps.

> 1) It takes a very long time to display a map : close to 2 minutes
> for a 1700 x 1200 pixels / 8 bits colors / 71 dpi / 2.2 Mb / .xpm
> file. Every time I ask for zoom in, zoom out,or slide the map, it
> takes the same amount of time to redisplay.

That can be solved by splitting up the map into several much smaller
maps, so that as you zoom in, you only load the maps that will fit
in the current viewport and you skip the rest.

A large raster map is going to take a long time to load no matter
what.  One exception to this is USGS geoTIFF maps, which are
constructed in such a fashion that the Xastir code could be
optimized to load them more quickly under certain conditions by
skipping lines in the file.

You might try converting the file to a more compressed format, like
JPG or PNG, which should make the file itself much smaller and
decrease your map load time.  XPM is a rather verbose file format.


> 2) the maps does not show up at the right place . The previously
> describe map with the following .geo file :

> FILENAME m0103.xpm
> #
> TIEPOINT 0 0 -61.05650451 14.30427778
> TIEPOINT 1699 1298  -61.00951339 14.26864253
> #
> IMAGE SIZE 1700 1299

> is displayed, roughly, at :

> upper left corner :  14° 18.251 N   061° 03.396 W
> lower right corner : 14° 16.128 N   061° 00.558 W

Throwing the .GEO coordinates into Xastir's coordinate calculator, I
come up with these lat/longs:

    14° 18.257N, 061° 03.390W
    14° 16.118N, 061° 00.571W

So it looks like where you are seeing the map displayed is where you
told it to display in the .GEO file.  Where did you want it to
display?

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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