Hi Jody -- On 29/04/15 15:01, Jody Garnett wrote: > Could I ask you to test the following > branch: https://github.com/geotools/geotools/tree/matrix > > We are switching to a different matrix implementation and I have already > noticed a difference in accuracy. I would really appreciate your > testing and input on this change as it is one I am concerned about. >
Will do and report back ASAP. Cheers, Ben > For more information > see https://github.com/geotools/geotools/wiki/Change-from-vecmath-to-EJML > > -- > Jody Garnett > > On 7 April 2015 at 14:46, Benjamin Ducke <bendu...@fastmail.fm > <mailto:bendu...@fastmail.fm>> wrote: > > Dear All -- > > First of all: This is my first posting to this > list, and I would like to take the opportunity > and say a big "Thank You" to the developers of > GeoTools! Your library has allowed me to do some > immensely productive Java GIS coding. > > But now I've run into a dead end (or so it seems). > > I am trying to use GeoTools' "ProjectiveTransform(Builder)" > classes to transform the pixel coordinates of images > to real-world coordinates. I made some tests with > "AffineTransform" first and this worked fine, but > the images have a perspective distortion and a > simple affine transformation won't suffice. > > Then I tested "ProjectiveTransform" with some synthetic > data, and the results looked promising. However, with > real data, the transformation seems to go out of control. > > Below is a list of six points. On line "Transform", > you will find the image coordinates and the world > coordinates to which they are _supposed_ to map. > > Under "World", you find the _actual_ mappings and the > difference (in map units, meters). As you can see, > the two are way off, with a maximum distance of > 278 meters. Also note the huge RMS: > > PROJECTIVE FORWARD RESULTS (IMAGE TO WORLD): > RMS = 134.46109310005252 > Pt.: 1 > Transform: 138.2/385.3 -> 513356.295/280624.993. > World X = 513393.74146133795 (37.446461337967776). > World Y = 280638.165346099 (13.172346098988783). > Dist = 39.695694583763874 > Pt.: 2 > Transform: 1267.3/415.3 -> 513357.71/280624.795. > World X = 513482.11524025456 (124.40524025453487). > World Y = 280597.9072626728 (-26.8877373271971). > Dist = 127.2777051229511 > Pt.: 3 > Transform: 2516.7/509.4 -> 513359.273/280624.553. > World X = 513583.4260212551 (224.1530212551006). > World Y = 280556.36530408286 (-68.18769591714954). > Dist = 234.294982473546 > Pt.: 4 > Transform: 2517.4/1589.3 -> 513359.071/280623.21. > World X = 513637.1007852404 (278.0297852404183). > World Y = 280607.33684666886 (-15.873153331165668). > Dist = 278.48252813687935 > Pt.: 5 > Transform: 1510.2/1744.6 -> 513357.854/280623.122. > World X = 513573.2481027579 (215.39410275791306). > World Y = 280647.9796511657 (24.857651165744755). > Dist = 216.82371255092065 > Pt.: 6 > Transform: 237.0/1685.9 -> 513356.421/280623.314. > World X = 513480.8793013462 (124.4583013462252). > World Y = 280688.37563165755 (65.06163165753242). > Dist = 140.43818813958055 > > Now, I have tested the same data with QGIS and > its projective referencing mode and it manages > to hit the target spot-on. So the problem is not > that the image is too distorted for a projective > transform. The RMS should be at most a few cm. > > Also, if I scale the pixel coordinates to bring > them roughly into the same range as the real-world > coordinates (say multiply by one million), then > I get substantially better results (however, results > are still off the mark by several meters). This > leads me to suspect that there is a precision problem > involved here. > > I use a "ProjectiveTransformBuilder" with a list of > "MapPosition" to build the "ProjectiveTransform". I > have tried toying with > "MappedPosition.setAccuracy(double)", but no luck > (I also don't understand how to set the double > parameter). > > I have tested GeoTools 11 through 13 and am getting > the same results with each. > > If anyone could point me into the right direction > for solving this problem, I would be very grateful. > I will gladly elaborate and also send sample data > via PM if anyone wants to take a closer look. > > Thanks and best regards, > > Ben > > -- > Dr. Benjamin Ducke > {*} Geospatial Consultant > {*} GIS Developer > > Spatial technology for the masses, not the classes: > experience free and open source GIS at http://gvsigce.org > > > ------------------------------------------------------------------------------ > BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT > Develop your own process in accordance with the BPMN 2 standard > Learn Process modeling best practices with Bonita BPM through live > exercises > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- > event?utm_ > source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF > _______________________________________________ > GeoTools-GT2-Users mailing list > GeoTools-GT2-Users@lists.sourceforge.net > <mailto:GeoTools-GT2-Users@lists.sourceforge.net> > https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users > > -- Dr. Benjamin Ducke {*} Geospatial Consultant {*} GIS Developer Spatial technology for the masses, not the classes: experience free and open source GIS at http://gvsigce.org ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ GeoTools-GT2-Users mailing list GeoTools-GT2-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
