[aprssig] future problems with NWS radar images?
HamLists at ametx.com
Tue Mar 29 05:55:23 CST 2005
> -----Original Message-----
> From: Steve Dimse
> Posted At: Monday, March 28, 2005 11:03 PM
> Subject: Re: [aprssig] future problems with NWS radar images?
> geo files would need to be updated. If I read Pete's
> explanation correctly, it sounds like the present radar
> images are the ones which are not the orthogonal projection
> geo files expect, so perhaps new geo files with the new image
> projection, even without rotation, would be more accurate.
> Do I have that right Pete?
That is correct. The current single radar site gifs are not orthogonal,
they are stereographic centered on the radar site. I have tables at
http://www.aprs-is.net/wx/wxradarsites.htm which gives the corners for
You are also correct that there is only a few pixel difference since the
scale is only a 120 mile radius. However, that is can represent up to a
mile difference in the outer areas of the map. I use the stereographic
project in jFindu mapping for NWS radar images. The formulae that I use
are derived from
http://mathworld.wolfram.com/StereographicProjection.html As you
probably are already aware, there are some c libraries out there that
also do the different projections.
Pete Loveall AE5PL
mailto:pete at ae5pl.net
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