Hi Barry, SAGA has few simple but useful modules for extraction of features from grids. See:
> library(RSAGA) > rsaga.get.modules("grid_discretisation") $grid_discretisation code name interactive 1 0 Supervised Classification FALSE 2 1 Cluster Analysis for Grids FALSE 3 2 Grid Segmentation FALSE 4 3 Grid Segmentation (b) FALSE 5 4 Grid Skeletonization FALSE 6 NA <NA> FALSE 7 NA <NA> FALSE For multiple images, you can use either cluster analysis or supervised classification: > rsaga.get.usage("grid_discretisation", 0) SAGA CMD 2.0.3 library path: C:/Progra~1/saga_vc/modules library name: grid_discretisation module name : Supervised Classification Usage: 0 -GRIDS <str> -POLYGONS <str> [-FIELD <num>] -CLASSES <str> -RESULT <str> [-ML_PROB <str>] [-METHOD <num>] [-NORMALISE] [-ML_THRESHOLD <str>] -GRIDS:<str> Grids Grid list (input) -POLYGONS:<str> Training Areas Shapes (input) -FIELD:<num> Class Identifier Table field -CLASSES:<str> Class Information Table (output) -RESULT:<str> Classification Grid (output) -ML_PROB:<str> Distance/Probability Grid (optional output) -METHOD:<num> Method Choice Available Choices: [0] Minimum Distance [1] Maximum Likelihood -NORMALISE Normalise Boolean -ML_THRESHOLD:<str> Probability Threshold (Percent) Floating point Value Range: 0.000000 - 100.000000 You can also consider getting the statistics from grids for polygons: > rsaga.get.modules("shapes_grid") $shapes_grid code name interactive 1 0 Add Grid Values to Points FALSE 2 1 Get Grid Data for Shapes FALSE 3 2 Grid Statistics for Polygons FALSE 4 3 Grid Values to Points FALSE 5 4 Grid Values to Points (randomly) FALSE 6 5 Contour Lines from Grid FALSE 7 6 Vectorising Grid Classes FALSE 8 7 Clip Grid with Polygon FALSE 9 8 Gradient from Grid FALSE 10 NA <NA> FALSE 11 NA <NA> FALSE You will soon discover that there is not much literature that explains how to run processing and what does each parameter in SAGA means :( Unfortunately, Olaf does not have time to write up a user's manual for SAGA, but you can always zoom into the original code. I am sure that all algorithms come from some literature. E.g.: Kothe, R., Bock, M., 2006. Development and use in practice of SAGA modules for quality analysis of geodata. In Böhner, J., McCloy, K.R., Strobl, J. [Eds.]: SAGA – Analysis and Modelling Applications. Göttinger Geographische Abhandlungen, Vol.115. http://surfnet.dl.sourceforge.net/sourceforge/saga-gis/gga115_08.pdf HTH Tom Hengl http://spatial-analyst.net -----Original Message----- From: r-sig-geo-boun...@stat.math.ethz.ch [mailto:r-sig-geo-boun...@stat.math.ethz.ch] On Behalf Of Rawlins, Barry G Sent: Friday, February 27, 2009 3:06 PM To: r-sig-geo@stat.math.ethz.ch Subject: [R-sig-Geo] Feature Extraction - object based image analysis I have a colleague who is not familiar with R and we were discussing feature extraction from multiple images (air photos, satellite based etc.). He uses a commercial tool for feature extraction. Can anyone point me to a package in R that does this? I have done a search but not found such a function. It is not a procedure I am familiar with. Many thanks, Barry Dr Barry Rawlins Sustainable Soils Team Leader British Geological Survey Keyworth Nottingham NG12 5GG Direct tel: 0115 9363140 Mobile: 0788 4235473 homepage: http://barryrawlins.googlepages.com<http://barryrawlins.googlepages.com/> -- This message (and any attachments) is for the recipient ...{{dropped:8}} _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo