<div dir="ltr">Dear Mr Phil<div><br></div><div>I am very sorry I have to come to you with another question.</div><div>I have tried the equation that written at the web that you shared.</div><div><br></div><div>Since I just need short distance, then I use this equation</div><div><br></div><p style="color:rgb(0,0,0);font-family:"times new roman";font-size:medium">"A mathematically equivalent formula, which is less subject to rounding error for short distances is:</p><pre style="color:rgb(0,0,0)">d=2*asin(sqrt((sin((lat1-lat2)/2))^2 + </pre><div><span style="color:rgb(0,0,0)"> cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2))</span></div><div><br></div><div>But, when I tried to make calculation by using the equation, the result was wrong.</div><div><br></div><div>Do you have any idea? am I wring in choosing equation.</div><div><br></div><div>Thank you very much.</div><div><br></div><div>Best regards</div><div>wendi</div><div> </div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Nov 1, 2016 at 11:32 PM, HARVEY, PHILIP O NH-03 USAF AFMC 412 OSS/OSW <span dir="ltr"><<a href="mailto:philip.harvey.1@us.af.mil" target="_blank">philip.harvey.1@us.af.mil</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">See Ed Williams' Aviation Formulary at <a href="http://williams.best.vwh.net/avform.htm" rel="noreferrer" target="_blank">http://williams.best.vwh.net/<wbr>avform.htm</a> for great circle distance, etc formulas. The formula you desire is only requires 1 line and can easily be written into a function.<br>
<br>
Phil<br>
<div><div class="h5"><br>
<br>
-----Original Message-----<br>
From: <a href="mailto:gradsusr-bounces@gradsusr.org">gradsusr-bounces@gradsusr.org</a> [mailto:<a href="mailto:gradsusr-bounces@gradsusr.org">gradsusr-bounces@<wbr>gradsusr.org</a>] On Behalf Of wendi harjupa<br>
Sent: Tuesday, November 01, 2016 2:01 AM<br>
To: GrADS Users Forum <<a href="mailto:gradsusr@gradsusr.org">gradsusr@gradsusr.org</a>><br>
Subject: [gradsusr] convert world coordinate distance to real distance (km)<br>
<br>
Dear every one<br>
<br>
I have problem with converting distance in world coordinate to distance,<br>
<br>
I have map with<br>
lon = 135 135.5<br>
lat = 34.5 35<br>
<br>
I want to set lon =135, as 0 km, and lat=34.5 as 0 km.<br>
as we know that 1 deg is about 110 km.<br>
<br>
Is there any function in grads that can directly convert the world coordinat distance to real distance (km)?<br>
<br>
Please, any help would be very appreciate.<br>
<br>
thank you<br>
regards,<br>
wendi<br>
<br>
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