[Xastir] More on radar problem

[Gerry Creager]

I'll find the explicit reference (all I can find is the full-US mosaic 
right now) but using Delorme is a real poor hack since the projections 
are different between RIDGE and Street Atlas.  At least from a GIS geek 
perspective.

gerry

James Jolin wrote:
> Alex Carver wrote:
>> --- On Sun, 12/6/09, James Jolin <jjolin at itol.com> wrote:
>>  
>>> Alex,
>>> How did you set up the geo file?  Did you take an
>>> existing file and change the url or did you start from
>>> scratch?  I know next to nothing about geo files.
>>> Jim
>>> WA9ARB
>>>     
>>
>> The easiest way is to follow along with one of the default GEO files 
>> and make the appropriate modifications.
>>
>> Here's an example of my GEO for the Atlanta area RIDGE radar (watch 
>> out for word wraps):
>>
>> #                       X               Y               
>> Long            Lat
>> URL     http://www.srh.noaa.gov/ridge/RadarImg/N0R/FFC_N0R_0.gif
>> TIEPOINT                0               0               
>> -87.37500       35.58083
>> TIEPOINT                620             620             
>> -82.00217       31.14133
>> IMAGESIZE 620 620
>> REFRESH 60
>> TRANSPARENT 0x0
>> PROJECTION LatLon
>>
>> The TIEPOINT directives will assign a specific pixel coordinate (X,Y) 
>> to a specific lat/long.  Pixel 0,0 is upper left, and 620x620 is the 
>> lower right most pixel on my RIDGE image (the image itself is also 
>> 620x620 in this case).  You need two TIEPOINTs so that Xastir can 
>> appropriately place the image.  The IMAGESIZE tells Xastir how big the 
>> radar file is in pixels (again 620x620 for the Atlanta RIDGE).
>>
>> After that, just fix the URL accordingly.
>>
>> The more accurate the points, the better the radar will line up with 
>> your maps.  I used Delorme Street Atlas to find a couple known points 
>> in the RIDGE data and then worked my way back to the corners.  You 
>> don't have to use the corners of the image file, any two points will 
>> do since Xastir knows about the overall image size using the IMAGESIZE 
>> directive.
>>
>> You may have to play around with the TRANSPARENT directive which tells 
>> Xastir what color is defined to be transparent for overlay purposes.
>>
>>
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>>
>>   
> thanks, Alex...looks like a nice evening project.
> Jim
> 
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