Hi Peter; Thank you very much for the references. Actually I was considering too to utilize the Natural Neighbours concept, not only for nearest neighbour identification, but also for interpolating the values attributed to spatial points. I guess this time a dynamic version of needs to be implemented, since one needs to adapt the tesellation with the newly inserted query point at eachnew query. (assume that I have a set of points with their associated depth values, and I use this set as a source of querying new points with unknown depth)
Actually if it is not a problem for you, I would be pleased to see the code to get a better understanding about the algorithms involved. Best regards, Yilmaz On Fri, Oct 2, 2009 at 8:24 AM, Peter J Halls <p.ha...@york.ac.uk> wrote: > Yilmaz, > > I'll leave the GEOS / Windows compilation bit to those who know! However, > I can help on the nearest neighbour issue as I have done some research in > this area. To do it properly is non-trivial: indeed, it is effectively a > Dirichlet / Voronoi tessellation problem. For an outline and some > bibliography see > Halls, P.J, Bulling, M., White, P.C.L., Garland, L., Harris, S., 2001, > Dirichlet neighbours: revisiting Dirichlet tessellation for neighbourhood > analysis, Computers, Environment and Urban Systems (CEUS) 25 pp105-117. > This is based on Robin Sibson and Peter Green's 'Natural Neighbours' > algorithm, Green, P., & Sibson, R, 1978, Computing Dirichlet tessellations > in the plane; Computer Journal 21 pp168-173. > This approach appears to be one of the fastest and most reliable algorithms > for computing a Dirichlet Tessellation. Once you have that tessellation, > the neighbours of each point are easy to identify - indeed, they 'fall out' > of the structure used by the Green and Sibson algorithm. > > My software is written in Simula (the 'original' object programming > language), using the CIM Open Source Simula cross-compiler from the > University of Oslo and the OGR library via c calls. My 'neighbours' program > computes for each point in a dataset the set of 'natural neighbours' for > each point, identifies that which is nearest and reports the distances and > angles to each neighbour. CIM is written in c and cross compiles into c. I > use the Cygwin interface on Windows and the gcc compilers: I cannot comment > on building CIM in Visual Studio. However, should you wish, I would be > willing to supply you with my source. > > Best wishes, > > Peter > > Yilmaz Arslanoglu wrote: >> >> Hi; >> >> I am trying to build and install the GDAL library on Windows XP >> using the following commands: >> >> nmake /f makefile.vc >> nmake /f makefile.vc install >> nmake /f makefile.vc devinstall >> >> In order to build with GEOS support, I uncommented the lines >> in the "nmake.opt" as follows: >> >> GEOS_DIR=C:\geos-3.1.1 >> GEOS_CFLAGS = -I$(GEOS_DIR)/capi -I$(GEOS_DIR)/source/headers -DHAVE_GEOS >> GEOS_LIB = $(GEOS_DIR)/source/geos_c_i.lib >> >> However, I still get the same .dll and .lib files as if no GEOS >> support was turned on >> (the sizes are exactly the same). When I try to call >> "OGRGeometry::Contains()" method, >> I also get the error: >> >> "ERROR 6: GEOS support not enabled." >> >> What could be wrong? >> >> 2) I was also wondering whether OGR library provides a kind of nearest >> neighbour finding facilities? >> If not, does anybody know any library that could be integrated with >> OGR for this purpose? >> I plan to use it to find the n nearest sounding points (SOUNDG) >> given a point, to make a prediction >> about its depth. >> >> 3) Finally, is there any facility in OGR for querying a layer such that >> it will only return the features on it, which contain a given >> point as parameter? >> Because I could not come up with an SQL statement to perform this task. >> Actually I was planning to use this on the DEPARE (depth area) layer on >> an S-57 file to find the depth area polygon that covers the given >> point. >> >> Any idea or references about these issues would greatly be >> appreciated. >> >> Best regards, >> Yilmaz >> _______________________________________________ >> gdal-dev mailing list >> gdal-dev@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/gdal-dev > > -- > -------------------------------------------------------------------------------- > Peter J Halls, GIS Advisor, University of York > Telephone: 01904 433806 Fax: 01904 433740 > Snail mail: Computing Service, University of York, Heslington, York YO10 5DD > This message has the status of a private and personal communication > -------------------------------------------------------------------------------- > _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev