I have 9.3, but I am no arcmap wizard. If you can give me step-by-step instructions I can tell you what happens and/or attach screen shots.
On Fri, Nov 7, 2008 at 9:21 AM, Larry Becker <[EMAIL PROTECTED]> wrote: > No one has mentioned that the new ArcGIS 9.3 will create Geodesic buffers > if: > > "Features to be buffered are points or multipoints. > Input features are in geographic coordinates. > Buffer distance is in Euclidian linear units." > > "Output buffer polygons will take into account that longitudinal distance > varies with latitude." > > Taken from the summer issue of ArcUSER: > http://esri.com/news/arcuser/1008/files/top10gp.pdf > > I don't have 9.3 yet so I can't try this. Has anyone else? I guess the > fact that ESRI limits the input to points says that they haven't really > solved this problem either. > > regards, > Larry Becker > > > On Thu, Nov 6, 2008 at 4:56 PM, Michael Michaud <[EMAIL PROTECTED]>wrote: > >> >> Hum... consider two lines that do barely touch. You have an intersection >>> point. If the transformation changes the intersection points, it would >>> mean that it's possible that after reprojection the two lines do >>> not touch anymore, thereby changing their topological relationship. >>> >>> I have vague memories of continuous transformations never altering >>> the topological relationships between the transformed geometries, >>> but I may have dreamt about it :) >>> >> I think it may be true with shapes which are not discretized. But we >> always use a discrete representation and we generally suppose that >> coordinates can be linearly interpolated between points. But interpolation >> function should not be the same in geodetic space and in projected space >> (the precise image of a straight segment - or a geodetic line - on Earth's >> surface is generally not a straight segment in the projected plan). The >> error is hidden as far as we do not need to interpolate, but can appear as >> soon as we need to interpolate (as in intersection computation for example). >> >> Michaël >> >> Cheers >>> Andrea >>> >>> >> _______________________________________________ >> jts-devel mailing list >> [email protected] >> http://lists.refractions.net/mailman/listinfo/jts-devel >> > > > > -- > http://amusingprogrammer.blogspot.com/ > > _______________________________________________ > jts-devel mailing list > [email protected] > http://lists.refractions.net/mailman/listinfo/jts-devel > >
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