[Xastir] Interesting APRSdos map!

[Gerry Creager N5JXS]

IN general terms, we should honor 0-360 deg, and -180 - 180 deg.  We 
generally think in terms of the latter; to preserve that, we need to 
convert 0-360 so that 180-360 is twisted to -180 - 0 (am I making sense?).

Another random thought:  If we were Pacific-centric, we'd almost 
certainly make our longitude consistent with the 0-360 model...

There's an outside chance APRSdos did cartography right by intent. 
Higher probability it was by chance.

gerry

Henk de Groot wrote:
> Hello,
> 
> Wayne Carvalho from Hawaii send me a map the other day for conversion to 
> a pocket APRS map. It turned out to be an APRSdos map, which I have not 
> dealt with before.
> 
> Finally yesterday I started looking at the APRSdos map format, just 
> basically trying to figure out the corner points. My math kept showing 
> strange results so I looked at the Xastir code how it decodes these 
> maps. It turns out the map covers a very big area, but more strangely it 
> goes from 90:00:00.00E to 306:02:41.28E. Normally E/W values do never 
> get bigger than 180 degrees, 181:00:00.00E would be written as 
> 179:00:00.00W. On Xastir the map shows up, but half of it sticks outside 
> the earth's grid on the right hand side... I can't change the 
> 306:02:41.28E value to a west value since then the right border would be 
> more left than the left border (hmm,how does one say this, does it still 
> make sense?).
> 
> Anyway, PocketAPRS has hard borders at 180W and 180E which cannot be 
> crossed, so a map smack in the middle over his area will not work. But 
> if APRSdos is able the show this map correcly, I assume Xastir should 
> too, so it should have a notion that the earth is round (at least a 
> cylinder approximation for this one...).
> 
> I'm very interested in your reaction and if someone can make it show up 
> correctly in Xastir...
> 
> For people who want to try, I stored the map at:
> http://www.homepages.hetnet.nl/~pe1dnn/pac_west.zip
> 
> Kind regards,
> 
> Henk.
> 
> P.S. Of course after this is fixed the next challenge is a polar map of 
> the North Pole or the Antartic area... I wonder if APRSdos can do that 
> too...
> 
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Network Engineering -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
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Office: 903A Eller Bldg, TAMU, College Station, TX 77843