Object based classification RSGISLib Training shapefiles from QGIS

[Alpesh]

Hello Sir,

I want to use RSGISLib for Object based classification. I have  followed the training manual of RSGISLib,

But stuck after generating clumps.

In next step I need to provide shapefiles (one for each class).

I have tried a lot after installing QGIS , OTB  and googled a lot for above step.

But no meaningful result.

Sir,  kindly give steps / doc / tutorial   for generation of shapefiles required in RSGISLib for OOC using QGIS.

Without this,   next steps of the training manual of RSGISLib are not possible.

I will be very thankful for your valuable suggestion / help.

[Daniel Clewley]

Hi,

For the supervised classification it assumes you have some training data or are able to generate some and that the training data can be represented as polygons in a shapefile.

For example if you want to classify forests and you have some areas which you know are forest you can use as training data you could open up maps / satellite data in QGIS and draw polygons for these areas of known forest.

This guide gives an overview of creating a shapefile in QGIS: https://www.qgistutorials.com/en/docs/digitizing_basics.html see further down the guide for details on how to make a polygon (rather than line).

Thanks,

Dan

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[Alpesh Patel]

Thanks a lot Mr. Daniel for your helpful suggestions.

I have seen the complete document suggested by you and its very helpful to me for creating shapefiles.

But still I have been stuck at bellow questions regarding training data for each class:

Suppose, in my segmented (clumps)  image I have
      Number of segments = 3000
     Number of class =     3
     Number of segments for each class = 1000

Q:1   Than for training shapefiles of each class, how many segments (polygons) I should manually draw for training ?

         I means approximately 20 or 50 or  500 or 1000 or 10000 polygons of in shapefiles of each class.

Q:2   Should I generate this shapefiles from my study area segmented (clumps) image?

                    or

         I can make it from any map / image having similar type of class?

Sir, kindly give your valuable suggestion for  above questions.

Regards,

Prof. Alpesh M Patel
Asst. Prof.,
EC Department,
VGEC Chandkheda