Mr Figuers wrote: > degraded (both in the numeric calculations and in comparing puck location with > the map on the screen). The more control points that were included, the > greater the location errors. The best accuracy always occurred with only 3 > control points. > > why? Because any 3 points can be made to match any other 3 points, i.e a three point registration is really no registration at all. If location errors increase with more control points, this is probably a sign that the projection of the printed map is different from that of the table you want to digitize into. In any case, accuracy *should* increase with more control points (given that all points are correctly identified). If the printed map has a coordinate grid of some sort, it is generally a good advice to use that for the control points. You may also want to check the calibration of the digitizing table. Best regards, Mats.E -- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :Email/ [EMAIL PROTECTED] ICQ#9517386 : :---------------------------------------------------------------------: :Mail/ GISKRAFT, Mats Elfstroem, Vaepplingv 21, SE-227 38 LUND, SWEDEN: :Phones: +46 46 145959, +46 70 595 3935 : ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ---------------------------------------------------------------------- To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED]
