On Sat, Feb 4, 2012 at 7:49 AM, Robert Buckley <robertdbuck...@yahoo.com> wrote: > Hi, > > If mapclients are using EPSG:900913 (Google / Web Mercator) in a > web-application there are a couple of problems when using the mapfish print > module to export to pdf. > > 1. massive inaccuracy when measuring > 2. scalebar is unusable due to 1. > > I was just wondering if anyone had come accross any solutions to these > problems, or are maps just produced without scale bars/ or with scalebars > which are wrong?
I am not sure if this is relevant or not, but EPSG:900913 is probably one of the worst projections to measure on, as it deforms distances in a very dramatic way, the more you move to north, the more you get distortions (the distortion factor diverges to infinite as you reach the poles). If you need to print the map and measure it please use one official projection for your state, each state has a small set of projections, different from state from state and sometimes from point to point (e.g., Italy is normally divided in two slices) that allow some accurate paper measuring up to the 1:100.000 scale. As you get closer to the ground often not even the state ones allow for accurate measuring on paper. For example, in the italian case at the borders of the EPSG:3002/EPSG:3003 projections you actually have a 20m error induced by the projection. At 1:100000 that is not a big deal, it would be 0.2mm on paper, e.g., smaller than the error you'd make by manually taking the measure on paper, but at 1:10000 it would already be 2mm on paper, something big enough to make a difference for anybody (btw, the error is that big if you measure some large object, going from the central meridian of the projection to its east/west border, not when measuring a small object) Cheers Andrea -- ------------------------------------------------------- Ing. Andrea Aime GeoSolutions S.A.S. Tech lead Via Poggio alle Viti 1187 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 962313 mob: +39 339 8844549 http://www.geo-solutions.it http://geo-solutions.blogspot.com/ http://www.youtube.com/user/GeoSolutionsIT http://www.linkedin.com/in/andreaaime http://twitter.com/geowolf ------------------------------------------------------- ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Geoserver-users mailing list Geoserver-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geoserver-users
