The maps are in Mercator projection which doesn't preserve sizes but preserves shapes and bearings. This is your "problem".
Some more information about it: http://wiki.openstreetmap.org/index.php/Mercator http://en.wikipedia.org/wiki/Mercator_projection 2008/6/30 <[EMAIL PROTECTED]>: > > Hi, > > Maybe I am misunderstanding things, but something just doesn't seem to add > up when choosing longitudes for exporting a map. > If I want to export two maps at significantly different longitudes, but the > same scale and map size for each (1280 x 1024), shouldn't the longitudinal > width (number of degrees) be different for each map? I'm getting the same > for each. > > Here's the scenarios, both in Australia. > > #1. Adelaide. > Select -34.6, 138.0, 139.61, -35.6536 at a scale of 1:500000 > Exporting this gives a 1280 x 1024 image. > > #2 Darwin. > Select -12.3, 130.0, 131.61, -13.555 also at a scale of 1:500000 > Exporting this also gives a 1280 x 1024 image. > > The latitude range varies with each (1.0536 vs 1.255 degrees), which is as > per expected because of Earth's eliptical bulge near the Equator. > However, the longitude range is the same for each (1.61 degrees). Given > this, I would expect the image width of each to be significantly different > (Adelaide smaller as is further from the Equator where one degree longitude > is less miles than nearer the Equator). > > The scale of the images seem proportional so it seems to me that the > longitude values for the images must be incorrect. How can the width of both > exported images equal 1.61 degrees of longitude when one image is 22.3 > degrees further North than the other? > > Kind Regards, > > Luke Angel > Technical Communications Officer - Commercial Market > Clipsal Integrated Systems > > > > Fifth Street > Bowden. SA 5007 > Telephone +61 8 8345 9509 > Facsimile +61 8 8346 0573 > [EMAIL PROTECTED] > > > > This email and any attached files with it ("this communication") are > confidential and are intended solely for the use of the addressee. The > unauthorised use, dissemination, forwarding, printing or copying of this > communication is strictly prohibited. If you have received this > communication in error, please notify us immediately by reply email and > delete this communication. Any views expressed in this communication are > those of the individual sender, except where the sender specifically states > them to be the views of Clipsal Australia Pty Ltd. > _______________________________________________ > newbies mailing list > [email protected] > http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/newbies > > -- Lauri Hahne _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/newbies
