Supervised classification (Tutorial)

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(Training phase)
(Classification phase)
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* Set {{button|text=Output pixel type}} to '''uint8'''
 
* Set {{button|text=Output pixel type}} to '''uint8'''
 
* Save the {{button|text=Output image}} as '''svm_classification.tif'''.
 
* Save the {{button|text=Output image}} as '''svm_classification.tif'''.
* Uncheck Confidence map: Open output file after running algorithm.
+
* Uncheck Confidence map: ''Open output file after running algorithm''.
  
 
=Per pixel classification with OTB standalone=
 
=Per pixel classification with OTB standalone=

Revision as of 13:44, 4 July 2019

Contents

Per pixel classification with QGIS and OTB processing plugin

Training phase

  • In the search engine of Processing Toolbox, type TrainImages and open TrainImagesClassifer.
  • In the Input Image List select a (or optional: several) multispectral images: Subset_S2A_MSIL2A_20170619T_MUL.tif .
  • In the Validation Vector Data List and choose a vector polygon file with an independent sample of validation areas: lucc_validation.shp.
  • Type C_ID in the {button|text=Field Name}} text field.
  • Choose Support Vector Machine Classifer libsvm from the drop down list.
  • SVM Model Type is csvc
  • The SVM Kernel Type is Linear.
  • Switch checkbox Parameters optimization on.
  • In the Output model specify an model file: e.g. lucc_svm.model
  • Define an output file for Output confusion matrix or contingency table (e.g.lucc_svm_confusion.csv).
  • Click Run.
  • Click on the Log tab and inspect the quality measures: Precision, Recall, F-score and Kappa index.

Qgis otb trainimages.png

Classification phase

  • In the search engine of Processing Toolbox, type ImageClassifier and double click ImageClassifier.
  • Set Subset_S2A_MSIL2A_20170619T_MUL.tif as Input image.
  • Set Input _mask to blank (top of drop-down list).
  • Set lucc_svm.model as Model file.
  • Set Output pixel type to uint8
  • Save the Output image as svm_classification.tif.
  • Uncheck Confidence map: Open output file after running algorithm.

Per pixel classification with OTB standalone

Training phase

  • 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: lucc_training_input.shp.
  • Activate the checkbox Validation Vector Data List and choose a vector polygon file with an independent sample of validation areas: lucc_validation.shp
  • In the Output model specify an output model file: e.g. lucc_svm.model
  • Activate the checkbox and save the Output confusion matrix or contingency table as lucc_svm_confusion.csv.
  • In the Bound sample number by minimum field type 1.
  • Set the training and validation sample ratio to 0. (0 = all training data).
  • Mark C_ID in the Field containing the class integer label (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 Linear.
  • The SVM Model Type is C support vector classification.
  • Switch the Parameters optimization to on.
  • Check user defined seed and enter an integer value.
  • Click on Execute.

Otb trainimages.png

Classification phase

  • 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.

Qgis-otb-ImageClassifier SVM.png

  • 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 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_classification.tif in the TOC and select Properties --> Style --> Style --> Load Style.
    • Select the style file classification.qml. OK.
    • Open the text file ConfusionMatrixSVM.csv and calculate overall, user and producer accuracies.
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