Supervised classification (Tutorial)

From AWF-Wiki
(Difference between revisions)
Jump to: navigation, search
(→‎Train image classifier)
(→‎Classification)
Line 20: Line 20:
  
 
=== Classification===
 
=== Classification===
−
# Add the cloud mask ''cloud_shadow_mask.tif'' into QGIS. It should be available in the course data.
 
 
# Open {{mitem|text=Orfeo Toolbox --> Image Classification}} (see figure '''C''').
 
# Open {{mitem|text=Orfeo Toolbox --> Image Classification}} (see figure '''C''').
−
# Set ''Subset_S2A_MSIL2A_20170619T_B12_BOA.tif'' as {{button|text=Input image}}.
+
# Set ''Subset_S2A_MSIL2A_20170619T_MUL_BOA.tif'' as {{button|text=Input image}}.
−
# Set ''cloud_shadow_mask.tif'' as {{button|text=Input mask}}.
+
 
# Set ''SVM.model'' as {{button|text=Model file}}.
 
# Set ''SVM.model'' as {{button|text=Model file}}.
−
# Set ''SUB_LC81950242013188LGN00_MUL.tif.xml'' as {{button|text=Statistical file}}.
+
# Set ''Subset_S2A_MSIL2A_20170619T_MUL_BOA.xml'' as {{button|text=Statistical file}}.
 
# Save the {{button|text=Output image}} as ''su_svm.tif''.
 
# Save the {{button|text=Output image}} as ''su_svm.tif''.
 
# Evaluate classification results.
 
# Evaluate classification results.
 
## Add the classification result ''su_svm.tif'' to QGIS.
 
## Add the classification result ''su_svm.tif'' to QGIS.
 
## Right click ''su_svm.tif'' in the [[TOC]] and select {{mitem|text=Properties --> Style --> Style --> Load Style}}.
 
## Right click ''su_svm.tif'' in the [[TOC]] and select {{mitem|text=Properties --> Style --> Style --> Load Style}}.
−
## Load ''classifcation.qml'', which should be available in the course data.
+
## Load ''lab05_MinDist.qml''.
−
## Open the Google Maps Layer under {{mitem|text=Web --> ObenLayers plugin --> Add Google Satellite layer}} and look for misclassification.
+
  
 
=== Compute a confusion matrix with independent reference data ===
 
=== Compute a confusion matrix with independent reference data ===

Revision as of 21:18, 13 May 2018

Contents

Classification with Orfeo Toolbox

Image statistics

  1. Add the Sentinel-2 imagery Subset_S2A_MSIL2A_20170619T_MUL_BOA.tif into a QGIS project.
  2. Calculate mean and standard error for each band of the Sentinel-2 imagery using the OTB Graphical User Interface.
  • In the Search box on the Windows Start menu type OSGeo4W Shell. You should be able to open the shell by clicking on it.
  • Type into the shell: otbgui_ComputeImagesStatistics.

Select a multiband input file and an output XML file as seen in the screenshot. Qgis ComputeImagesStatistics.png

Train image classifier

  1. Add the training areas as vector polygon file lab05_training_input.shp into QGIS.
  2. Open Orfeo Toolbox --> TrainImageClassifier (libsvm) to use the Support Vector Machine SVM algorithm (see figure B).
  3. Set Subset_S2A_MSIL2A_20170619T_MUL_BOA.tif as Input image list.
  4. Set lab05_training_input.shp as Input vector list.
  5. Set Subset_S2A_MSIL2A_20170619T_MUL_BOA.tif.xml as Input XML image statistics file.
  6. Set Name of discrimination field to C_ID (C_ID refers to the column that contains the LUC code).
  7. Save the Output confusion matrix as ConfusionMatrixSVM.csv.
  8. Save the Output model as SVM.model.
  9. Calculation of accuracies :
    Open ConfusionMatrixSVM.csv in LibreOffice or MS Excel and calculate overall, producer and consumer accuracies.

Classification

  1. Open Orfeo Toolbox --> Image Classification (see figure C).
  2. Set Subset_S2A_MSIL2A_20170619T_MUL_BOA.tif as Input image.
  3. Set SVM.model as Model file.
  4. Set Subset_S2A_MSIL2A_20170619T_MUL_BOA.xml as Statistical file.
  5. Save the Output image as su_svm.tif.
  6. Evaluate classification results.
    1. Add the classification result su_svm.tif to QGIS.
    2. Right click su_svm.tif in the TOC and select Properties --> Style --> Style --> Load Style.
    3. Load lab05_MinDist.qml.

Compute a confusion matrix with independent reference data

  1. Open Orfeo Toolbox --> ComputeConfusionMatrix (Vector) (see figure D).
  2. Set su_svm.tif as Input image.
  3. Set train_systematic_seg.shp as Input reference vector data.
  4. Set Field name to C_ID.



Figures

Figure A: Dialogues of the Compute images second order statistics
Figure B: Dialogues of the TrainImageClassifier (libsvm)
Figure C: Dialogues of the Image Classification
Figure D: Dialogues of the ComputeConfusionMatrix (Vector)
Retrieved from "http://wiki.awf.forst.uni-goettingen.de/wiki/index.php?title=Supervised_classification_(Tutorial)&oldid=14489"
Personal tools
Namespaces

Variants
Actions
Navigation
Development
Toolbox
Print/export