Supervised classification (Tutorial)

Classification with Orfeo Toolbox

Training per-pixel classifiers

• Type into the search box of the Windows taskbar: mapla.bat. Click on mapla.bat to open Monteverdi Application Launcher.
• In the search engine of mapla, type TrainImages and double click TrainImagesClassifer.
• In the Input Image List click on + and select a (or optional: several) multispectral images: Subset_S2A_MSIL2A_20170619T_MUL.tif .
• In the Input Vector Data List choose a vector polygon file with training areas: lab07_training_input.shp.
• Activate the checkbox Validation Vector Data List and choose a vector polygon file with an independent sample of validation areas: lab07_validation_input.shp
• In the Output model specify an output model file: e.g. SVM.model
• Activate the checkbox and save the Output confusion matrix or contingency table as ConfusionMatrixSVM.csv.
• In the Bound sample number by minimum field type 1.
• Set the training and validation sample ratio to 0. (0 = all training data).
• Set Field containing the class integer label to C_ID (C_ID refers to the column that contains the LUC code in the training and validation vector file).
• Choose LibSVM classifier from the drop down list as Classifier to use for the training.
• The SVM Kernel Type is Gaussian radial basis function.
• Switch the Parameters optimization to on.
• Set user defined seed with an integer value.
• Click on Execute.

500px

Classification

• In the search engine of mapla, type ImageClassifier and double click ImageClassifier
• Set Subset_S2A_MSIL2A_20170619T_MUL.tif as Input image.
• Set SVM.model as Model file.
• Save the Output image as svm_classification.tif.

• Evaluate classification results:
  • Load the multispectral Sentinel-2 image Subset_S2A_MSIL2A_20170619T_MUL.tif into QGIS.
  • Data source Manager --> Browser --> XYZ Tiles. Select Google Satellite as background layer.
  • Load the European Urban Atlas as vector layer D:\user\hfuchs\qgis1819\Uebung\geodata_lab01\vector\DE021L1_GOTTINGEN\ Subset-Goe_DE021L1_GOTTINGEN_UA2012_UTM32N.shp
  • Add svm_classification.tif to the QGIS project.
  • Download the style file classifcation.qml from Stud.IP.
  • Right click svm_classifcation.tif in the TOC and select Properties --> Style --> Style --> Load Style.
  • Select the style file classification.qml. OK