Readig raster files

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luisadieze

Do the TIF files need some specific properties to be read by Ocelet?

I'm trying to import a TIF file gotten from ArcGIS, but got an error from Ocelet.

Thanks!

padeg

Hi,
Well it has to be a georeferenced geotiff file.
I don't know of another constraint.
Maybe if you give us a copy of the error message you get, and the definition code of your datafacer we would be able to help you more precisely on this.

luisadieze

Hi, Pascal. Thanks for your answer!

The code I'm using is:

entity Pixel {
       property Cell cell             
   property Integer cover
}

datafacer LandCoverRaster {
   data RasterFile ("data/Cover2019.tif","EPSG:3116")
   match Pixel {
	   cover : "1"  
   }
}

 let lcRaster = new LandCoverRaster
 let landCover = lcRaster.readAllPixel 
 println("We have obtained "+landCover.size+" land cover pixels entities.")

And the error I got is:

java.lang.NullPointerException
   at fr.ocelet.runtime.raster.ORaster.getRaster(ORaster.java:272)
   at fr.ocelet.runtime.raster.ORaster.<init>(ORaster.java:153)
   at fr.ocelet.datafacer.ocltypes.RasterFile.createGrid(RasterFile.java:368)
   at fr.ocelet.model.riogrande.LandCoverRaster.readAllPixel(LandCoverRaster.java:19)
   at fr.ocelet.model.riogrande.RioGrande.run_RioGrande(RioGrande.java:97)
   at fr.ocelet.model.riogrande.RioGrande.main(RioGrande.java:32)
Exception in thread "main" java.lang.NullPointerException
   at fr.ocelet.datafacer.ocltypes.RasterFile.createGrid(RasterFile.java:374)
   at fr.ocelet.model.riogrande.LandCoverRaster.readAllPixel(LandCoverRaster.java:19)
   at fr.ocelet.model.riogrande.RioGrande.run_RioGrande(RioGrande.java:97)
   at fr.ocelet.model.riogrande.RioGrande.main(RioGrande.java:32)

I think the problem would be with the "cover" property. The image has 6 different colors where each one represents a land cover, and I was testing the code with one of them.

Thank you so much!

padeg

Do you get the same error message if you try with band 0 in the datafacer like this ?

match Pixel {
  cover: "0"
}

Asking that in the case your image has only one band ...

luisadieze

Thanks for your answer!

I exported another map from ArcGIS, and now I have no error using any value (0, 1, or 2) I have two more questions:

Is there any document where I can find more documentation about the usage of raster files in Ocelet? I'm not clear enough about the properties definition. Specifically, how can I combine the 3 bands to get the unique cover value, or how Ocelet understand it.
Can I export a raster to a kml? It would help to the verification tasks.

Thanks!

padeg

I'm afraid we do not have much more documentation to offer than what you already have about rasters manipulation, I agree it could be improved though.
I suggest that you have a look at the training session number 4 where we show how to calculate a NDVI using 2 bands out of a 4 bands satellite image. Maybe that would help you understand. Then you can still ask if there is something not clear enough
And I'm sorry we did not add the possibility to export a raster to a KML file from Ocelet. I will try to find a solution to help you do that and let you know.

luisadieze

Don't worry! I think it's easier to check another way to do the verification.

And thanks for the suggestion, I will look at the document