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Hello,<BR>
Im currently reviewing, testing, & attempting to change the grads2.0 source code in order to add a Mercator projection.<BR>
For those who are familiar in GrADS code/development, I could please use some assistance.<BR>
I've narrowed the projection routines to the gwxmap.c source file.<BR>
<BR>
I need help with:<BR>
2) how to create the "scaling" functions to correctly adjust the x,y values for the grads (internal) grid<BR>
1)determining in how many different places the scaling function needs to be applied, <BR>
(*since it seems there are a few different routines throughout all of the source code files where the<BR>
scaling is performed)<BR>
3)question: once the projection routine is implemented, it *should* take care of correctly scaling&drawing everything, including maps, grids, shapefiles (using shapefile extension), symbols, etc., is this correct?<BR>
<BR>
The functions for transforming from lat/lon to x,y are fairly simple: <BR>
<A href="http://en.wikipedia.org/wiki/Mercator_projection">http://en.wikipedia.org/wiki/Mercator_projection</A> <BR>
x=lon; <BR>
longitude remains unchanged<BR>
<BR>
y=ln(tan((pi/4)+(lat/2))); <BR>
latitude is variable<BR>
<BR>
so, I believe the key is just setting up the transformation functions and correctly referring to them throughout the source code.<BR>
<BR>
Most other graphics packages already include a Mercator projection, and it gets used alot for web mapipng/tiling, such as google earth & MS Virtual Earth.<BR>
Grads needs this...<BR>
<BR>
Those interested, please email me.<BR>
Thanks,,<BR>
P.Romero<BR>
<BR>
<BR>
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