[gradsusr] convert world coordinate distance to real distance (km)

Jeff Duda jeffduda319 at gmail.com
Tue Nov 1 11:02:07 EDT 2016

It sounds like you want to draw a plot with geographic coordinates replaced
by straight-line/distance coordinates instead. If that is the case, one
thing you can try is removing the PDEF line from your control file and
resetting your XDEF and YDEF lines to start at 0 (but keep the delta
value). That might work. If that doesn't work, you could also try turning
off the map projection in grads (set mproj off) and then using 'set xaxis'
and 'set yaxis' in clever ways to make it look like the map you draw is in
terms of linear distance. Good luck.

Jeff Duda

On Tue, Nov 1, 2016 at 9:32 AM, HARVEY, PHILIP O NH-03 USAF AFMC 412
OSS/OSW <philip.harvey.1 at us.af.mil> wrote:

> See Ed Williams' Aviation Formulary at http://williams.best.vwh.net/
> avform.htm for great circle distance, etc formulas.  The formula you
> desire is only requires 1 line and can easily be written into a function.
> Phil
> -----Original Message-----
> From: gradsusr-bounces at gradsusr.org [mailto:gradsusr-bounces at gradsusr.org]
> On Behalf Of wendi harjupa
> Sent: Tuesday, November 01, 2016 2:01 AM
> To: GrADS Users Forum <gradsusr at gradsusr.org>
> Subject: [gradsusr] convert world coordinate distance to real distance (km)
> Dear every one
> I have problem with converting distance in world coordinate to distance,
> I have map with
> lon = 135  135.5
> lat = 34.5   35
> I want to set lon =135, as 0 km, and lat=34.5 as 0 km.
> as we know that 1 deg is about 110 km.
> Is there any function in grads that can directly convert the world
> coordinat distance to real distance (km)?
> Please, any help would be very appreciate.
> thank you
> regards,
> wendi
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> gradsusr at gradsusr.org
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Jeff Duda
Post-doctoral research associate
University of Oklahoma School of Meteorology
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