madagascar2011 - 10 - otb object based image analysis

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orfeo-toolbox.org

Orfeo Toolbox Objects detectionOrfeo Toolbox

Objects detection

Stéphane MAY

stephane.may@cnes.fr

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orfeo-toolbox.org

Type of objects searched

Buildings

Roads

Rivers

Tents

Boats, planes

Etc.

Objects detection Objects detection

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Multiples approaches

Radiometry (if the object has a homogenous specific radiometry)

➢Thresholds on radiometry values

➢Spectral angle

Textures and contours

➢Local correlation, local mutal information

Contours

➢ HOG (Histogram of Gradient)

Segments (radiometry + contours)

➢ Computation of segments features and selection with SVM for example

Objects detectionObjects detection

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orfeo-toolbox.org

Menu File > Open

./output_fus1.tif

Menu Filtering > Feature extraction

Original data

Angle spectral on 1 point of the object

Angle spectral on 2nd point of the object

Others as you want

Menu Filtering > Band Math

if(min(im1b2, im1b3)<0.15,im1b1,0)

Try yours...

Use case 1 : objects detectionUse case 1 : objects detection

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Menu File > Open

./output_fus1.tif

Menu Filtering > Connected Segmentation Module

Mask Formulas

➢ndvi(b3,b4)<0.5

➢ (b1>300) * (b2 >400)

Display : Mask output. Click on Update.

Display : Masked image. Click on Update.

Connected component formulas

➢distance < 100 (Distance between adjacent pixels is less than 100)

➢ (p1b1>300) * (p1b2 >200)

Display : Segmentation output. Click on Update.

Use case 2 : connected component segmentation (1/3)Use case 2 : connected component segmentation (1/3)

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Objects min area

10

30

Display : Relabelling with small objects. Click on Update.

Object analysis formula

➢ (SHAPE_RegionRatio > 0.4) and (SHAPE_SizeOnBorder==0)

Display : Filter output. Click on Update.

In the viewer, right click on a segment : features are printed in the main

window

=> Now try your formulas !

Use case 2 : connected component segmentation (2/3)Use case 2 : connected component segmentation (2/3)

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Menu visualization > Viewer

Raster : reader0

Vector data to display : OuputVectorData

OutputVectorData

Right click > Export dataset

houses.shp (shapefile->SIG)

Use case 2 : connected component segmentation (3/3)Use case 2 : connected component segmentation (3/3)

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Connected component segmentationConnected component segmentation

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Menu File > Open

./output_fus1.tif

Menu Filtering > Mean shift module

Spatial radius : 5, Spectral value : 30, Min region : 50

Menu learning > Object labelling

Image to classify : Reader0

Labeled Image : MeanShift->LabeledImage

Add 1 class for object. Right click on twice on segments to select them.

Add 2nd class for non object. Right click on twice on segments to select

them.

Tab Learning. Classify.

Use case 3 : object labelling (1/2)Use case 3 : object labelling (1/2)

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orfeo-toolbox.org

Tab Objects.

➢Click on Sample (list of segments ID with features near the threshold

of SVM classification)

➢Select one segment ID. Select the other class. Right click to

redefine.

Tab Learning. Classify.

Save/quit

Use case 3 : object labelling (2/2)Use case 3 : object labelling (2/2)

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Object labelling (1/5)Object labelling (1/5)

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Object labelling (2/5)Object labelling (2/5)

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Object labelling (3/5)Object labelling (3/5)

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Object labelling (4/5)Object labelling (4/5)

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Object labelling (5/5)Object labelling (5/5)

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Thank you for your attention !

Monteverdi Monteverdi

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