Or you use a direct cylindric projection such as Cylindric Lambert, Behrman, Peters... :)<br><br><br>Jérôme<br><br><div class="gmail_quote">2011/1/6 Noel Zinn (cc) <span dir="ltr"><<a href="mailto:ndzinn@comcast.net">ndzinn@comcast.net</a>></span><br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Adam,<br>
<br>
What you're expecting works only on the Central Meridian (CM) and not<br>
elsewhere due to convergence of the meridians.<br>
<br>
Google "convergence of the meridians" for a fuller explanation.<br>
<br>
Noel<br>
<br>
Noel Zinn, Principal, Hydrometronics LLC<br>
+1-832-539-1472 (office), +1-281-221-0051 (cell)<br>
<a href="mailto:noel.zinn@hydrometronics.com">noel.zinn@hydrometronics.com</a> (email)<br>
<a href="http://www.hydrometronics.com" target="_blank">http://www.hydrometronics.com</a> (website)<br>
<div><div></div><div class="h5"><br>
-----Original Message-----<br>
From: Adam Dershowitz<br>
Sent: Wednesday, January 05, 2011 6:18 PM<br>
To: <a href="mailto:proj@lists.maptools.org">proj@lists.maptools.org</a><br>
Subject: [Proj] Lat/long to utm easting error<br>
<br>
I have run into something that I don't understand, and I hope someone can<br>
help explain.<br>
I was doing some conversions of points, and ran into a problem. I finally<br>
narrowed it down to the following:<br>
<br>
If I take two points, at the identical longitude, with a small change in<br>
latitude, and convert them each to UTM, I would expect nearly identical<br>
easting values. But I am not seeing that. For example:<br>
<br>
cs2cs +proj=latlong +datum=WGS84 +to +proj=utm +datum=WGS84 +zone=17 -r<br>
<br>
42d37'3.77503"N 83d59'35"W<br>
254524.57 4722707.58 0.00<br>
42d37'0.02186"N 83d59'35"W<br>
254520.47 4722591.80 0.00<br>
<br>
<br>
Above there is ~4 m easting difference, with just a small (~120m) change in<br>
latitude. Since these points are exactly North-south of each other,<br>
shouldn't they have the same easting, at least when they are this close to<br>
each other in latitude?<br>
<br>
Thanks much for any explanations,<br>
<br>
--Adam<br>
<br>
<br>
<br>
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</div></div></blockquote></div><br>