<div><p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no">Mr.
Gerald Evenden can clear your doubts about GEOD, since he is the
author of the program. I have used it only occasionally.</span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no">Anyway some
comments on your experiments: If you are comparing distances at millimetre level
be aware that when you round your geographic coordinates with 3 decimal places
in seconds you are introducing an error of up to 1.5 cm, so your distance can
be affected by a few centimetres. You can increase the decimal places of the
proj output (-W5, for 5 decimal places in seconds or use decimal degrees).</span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no">If your distances
are that small, i.e., just a few meters, then you can calculate the distance in
UTM just as the Euclidean distance (sqrt((x2-x1)^2+(y2-y1)^2)). The deformation in UTM projection (within one zone) is most of the times smaller than 40
cm per km, and you can calculate it and apply it if needed.</span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no">Regards</span></p><p class="MsoNormal"><br></p><p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no">Jose Gonçalves</span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-no-proof:no"> </span></p><br><div class="gmail_quote">2009/8/8 fernandohoze <span dir="ltr"><<a href="mailto:muranyum@yahoo.com">muranyum@yahoo.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im"><br>
<br>
José Alberto Gonçalves wrote:<br>
><br>
> In order to convert UTM-36N to long-lat with output in decimal degrees you<br>
> can use the following PROJ command line:<br>
> proj -I -f "%.9f" +ellps=WGS84 +proj=utm +zone=36<br>
<br>
</div>Thank you all for your replies. I tried the command José wrote (with -r flag<br>
- thanks Gerald) and it worked well. The command also works without<br>
reformatting the input.<br>
<br>
About calculating distance between two points... José, I examined the<br>
program you recommended but and I have some results but I need to make sure<br>
that they are correct. Here is what I did:<br>
<br>
First of all, here are the input points:<br>
<br>
4415488.923061 481668.789218<br>
4415490.272973 481668.977703<br>
<br>
I found latitude and longtitude using the following command:<br>
<br>
proj -r -I -f "%.9f" +ellps=WGS84 +proj=utm +zone=36<br>
<br>
Results:<br>
<br>
32.785593500 39.889265833<br>
32.785595667 39.889278000<br>
<br>
So, when I wrote these into Google Maps (in reverse order,) it correctly<br>
showed the points:<br>
<br>
39.889265833 32.785593500<br>
39.889278000 32.785595667<br>
<br>
Then, I executed the following geod command:<br>
<br>
geod +ellps=WGS84<br>
<br>
As input I wrote the above numbers. As output I received the latitude and<br>
longtitude in degree/minute/second format:<br>
<br>
39d53'21.357"N 32d47'8.137"E 180d<br>
39d53'21.401"N 32d47'8.144"E 180d<br>
<br>
Then, I executed this command for distance calculation:<br>
<br>
geod +ellps=WGS84 -I +units=km<br>
<br>
And entered the above coordinates as input:<br>
<br>
39d53'21.357"N 32d47'8.137"E 39d53'21.401"N 32d47'8.144"E<br>
<br>
The result was:<br>
<br>
6d59'12.829" -173d0'47.167" 0.001<br>
<br>
0.001 at the end of the result tells that the distance is around 0.001 km<br>
that is 1 meters. So, I tried the command with +units=m and the result was<br>
<br>
6d59'12.829" -173d0'47.167" 1.368<br>
<br>
That is 1.368 meters, which seems to be correct. I did the same calculation<br>
using <a href="http://www.movable-type.co.uk/scripts/latlong.html" target="_blank">http://www.movable-type.co.uk/scripts/latlong.html</a> this web page and<br>
the result was 0.001369 km. So, I guess I used the correct commands. The<br>
inputs I used for the web page were like that:<br>
<br>
Lat 1: 39 53 21.357N<br>
Long 1: 32 47 8.137E<br>
Lat 2: 39 53 21.401N<br>
Long 2: 32 47 8.144E<br>
<br>
There is one problem here that I don't get. When I use cm or dm for +units<br>
option, I still get 1.368 insted of 136.8 for cm and 13.86 for dm. Actually,<br>
if I don't use any +units option, I still get 1.368 as the result. Is there<br>
something wrong with the command I use or am I missing something?<br>
<br>
I also tried everything above with the following inputs:<br>
<br>
4415475.022910 481656.729116 918.850000<br>
4415473.636002 481656.540539 918.850000<br>
<br>
And in the end I got 1.195 as the results, which is reasonable. The web site<br>
gave 0.001194 km.<br>
<br>
I tried to write everything I did step by step. Could you please tell me if<br>
above calculations are correct or not. Also I would appreciate if you tell<br>
me a command that would do all the computation above.<br>
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