Length of a deg in metres

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Length of a deg in metres

 Hi, I am writing to python code to calculate the length (in metres) of a degree of longitude at a certain degree of latitude.  I would like to take various ellipsoid in mind (WGS84, GRS80, Clarke 1866...).  The goal is to find the right scale (or z factor) when making slope or shade raster models when x and y are in long/lat and z in feet or meters.  Can someone point me in the right direction to do this in using Proj?  Is Proj the best option for this? Thanks, Nicolas _______________________________________________ Proj mailing list [hidden email] http://lists.maptools.org/mailman/listinfo/proj
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Re: Length of a deg in metres

 I'm certain someone is going to be more knowledgeable than I, but I do sometimes go back to this answer at GIS.se to get some insight.The user shares some formulas for obtaining both the scale and z-factor.For other ellipsoids (the answer uses WGS84) it's a matter of determining the length of one degree (longitude) at the equator in metres. For WGS84 it's 111320m for example.The longitude is from the center of the area of interest.DonovanOn Thu, Nov 8, 2018 at 8:22 AM Nicolas Cadieux <[hidden email]> wrote:Hi, I am writing to python code to calculate the length (in metres) of a degree of longitude at a certain degree of latitude.  I would like to take various ellipsoid in mind (WGS84, GRS80, Clarke 1866...).  The goal is to find the right scale (or z factor) when making slope or shade raster models when x and y are in long/lat and z in feet or meters.  Can someone point me in the right direction to do this in using Proj?  Is Proj the best option for this? Thanks, Nicolas _______________________________________________ Proj mailing list [hidden email] http://lists.maptools.org/mailman/listinfo/proj _______________________________________________ Proj mailing list [hidden email] http://lists.maptools.org/mailman/listinfo/proj
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Re: Length of a deg in metres

 In reply to this post by Nicolas Cadieux Dunno about getting the result from proj.  The formula you want is given in https://en.wikipedia.org/wiki/Longitude#Length_of_a_degree_of_longitudeThis includes the ellipsoidal correction. On 11/8/18 10:18 AM, Nicolas Cadieux wrote: > Hi, > > I am writing to python code to calculate the length (in metres) of a > degree of longitude at a certain degree of latitude.  I would like to > take various ellipsoid in mind (WGS84, GRS80, Clarke 1866...).  The goal > is to find the right scale (or z factor) when making slope or shade > raster models when x and y are in long/lat and z in feet or meters.  Can > someone point me in the right direction to do this in using Proj?  Is > Proj the best option for this? > > Thanks, > > Nicolas > > _______________________________________________ > Proj mailing list > [hidden email] > http://lists.maptools.org/mailman/listinfo/proj> _______________________________________________ Proj mailing list [hidden email] http://lists.maptools.org/mailman/listinfo/proj