Just another piece of information (although don't remember where I read it): In general every 0.0001° of latitude equals ~ 11m. Longitude I think is the tough one... ;-)
On Thu, 2007-12-13 at 14:12 -0500, Patton, Eric wrote: > The width of a degree of longitude varies by latitude; meridians of longitude > converge to > a single point at the poles. Latitude varies as well, although considerably > less so, due to > the rotation of the earth slightly squashing the poles, and bulging the > Equator. > > ~ Eric. > > > -----Original Message----- > From: [EMAIL PROTECTED] on behalf of Gerald Nelson > Sent: Thu 12/13/2007 3:06 PM > To: 'Nikos Alexandris'; 'Michael Misun' > Cc: [email protected] > Subject: RE: [GRASS-user] (kein Betreff) > > I'm curious about the statement that "Lat-Long is not good to do distance > measurements" Someone else made a similar observation in a different > conversation recently too. I'm not a geographer so I'm probably missing > something but doesn't lat long just give you a point on the surface of the > earth and if you have two of these don't you more or less automatically know > the distance between them? > > Regards, Jerry > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Nikos Alexandris > Sent: Thursday, December 13, 2007 10:55 AM > To: Michael Misun > Cc: [email protected] > Subject: Re: [GRASS-user] (kein Betreff) > > Lat-Long is not good to do distance measurements! > > Why don't you reproject your lines in a "metric" projection system and > check the distances again. > > On Thu, 2007-12-13 at 14:03 +0100, Michael Misun wrote: > > hello everybody! > > i have a little problem: > > i want to set vertices on lines in a specified space (e.g. 2 km) in a lat > long coordinate system. > > i tried it with "v.to.points -vi .... dmax=0.03" and it works. the problem > is, that in the equatorial zone the space between the new added points is > about 1,7 km but up to the polzones the spacing is rather smaller and about > 600 m! > > can anybody help me with this problem? a want to have an equal space for > all vertices on my polylines > > > > michael -- Nikos Alexandris . Department of Remote Sensing & Landscape Information Systems Faculty of Forestry & Environmental Sciences, Albert-Ludwigs-University Freiburg . Tel. +49 (0) 761 203 3697 / Fax. +49 (0) 761 203 3701 / Skype: Nikos.Alexandris . Address: Tennenbacher str. 4, D-79106 Freiburg i. Br., Germany
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