Hi,

You should use TrainVectorClassifier instead of TrainImagesClassifier. This will train and produce a SVM model ("-io.out"  output file). You will have to set (at least) :

  • Input Vector Data (io.vd)
  • Output model (io.out)
  • Field names for training features (feat)
  • Field containing the class id for supervision (cfield, in your case it will be "training")
  • Classifier to use for the training (classifier  = libsvm)
However, before using this application, you will have to prepare a vector dataset with only your training polygons (polygons with a missing value in the field "training" will make the application crash).

Once you have the output model file (simple text/xml file) you can use it to do the classification on the full dataset (using application OGRLayerClassification).

Regards,
Guillaume

On 01/02/2017 11:54 PM, Geoffrey Balme wrote:
I forgot to say that after the segmentation, I added a field in my vector attribute table named "training", and I gave some numeric values to few polygons based on the classes I want the segments to be classified in (3 classes)

So now I'm with a few polygons having a training value, and most of the polygon having no training value, and I want to do the svm classification from this.

Le lundi 2 janvier 2017 23:52:47 UTC+1, Geoffrey Balme a écrit :
Hi Guillaume,

I'm also trying to do supervised object-based classification.
What I did so far is a meanshift segmentation on my satellite raster image.
Then I did TrainImagesClassifier (svm) on the vector results of the segmentation.
And at this point I'm not sure anymore what to do as there was no output on the previous step.
Could you guide me from the segmentation to have an object-based classification using SVM ?

(I tried to do OGRLayerClassification, but had no idea of what to put in the xml inputs etc..., the only input I have are my raster and my segmentation vector result)

Thank you !

Le jeudi 24 novembre 2016 14:46:00 UTC+1, Guillaume Pasero a écrit :

Hi Patricia,

If I understand right, you want to perform object-based classification.

In OTB-5.6.1 there is the application TrainVectorClassifier to train a classifier based on input geometries. You have to set several fields in the geometries you want to use for training :

- one field to indicate the class of the geometry

- several numeric fields to store the features attached to geometries.

The fields can be extracted from a raster with LSMSVectorization and modified with QGis.

After the training, you can either apply the model on the full set of geometries (with OGRLayerClassifier), or try to apply it on a raster (with ImageClassifier, but more difficult).

Regards,

Guillaume

On 11/24/2016 02:09 PM, Patricia Lourenco wrote:
Dear all,
I am new with OTB-Monteverdi 5-6-1.

I want to classify an image based on the segments created in the LSMVSVectorization (step 4 of the segmentation)using OTB/Monteverdi versions 5.6.1.
However, I am not being able to do it.

My questions are:

1. Which are the steps that I should take to do a classification based on segmentation?

2. Which OTB-Application should I use to select the segments for my classes?

Thank you, in advance, for your help.

Sincerely,
Patricia
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