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Question

Extract value in a raster and convert it

  • December 9, 2014
  • 6 replies
  • 189 views

Hi,

 

 

I'm trying to extract an especific value in a cell of the raster and after that i would like to convert it into a shapefile in a polygon format. I've tried to use the "RastertoPolygonCoercer" but failed. I'm recent user of FME so I don't get the feeling yet. Please any sugestion is welcome.

 

 

 

6 replies

takashi
Evangelist
  • December 9, 2014
Hi,

 

 

You can use these transformers to get cell values from a raster.

 

The PointOnRasterValueExtractor extracts the value of a cell specified by a point geometry. Output point will have cell value as its attribute.

 

The RasterCellCoercer transforms every cell into a point or a rectangle polygon. Resulting point or polygon will have cell value as its attribute or Z-value according to your parameter settings.

 

 

Takashi

  • Author
  • December 9, 2014
Unfortunately it seems that have a problem. The transformer RasterCellCoercer didn't' work correctly and appeared a mensage "Only features with raster geometry are expected". I am sure that my entry is a raster but this error I didn't understand.How can I solve this?

takashi
Evangelist
  • December 9, 2014
Could you please paste a screenshot that shows the situation - including the reader feature type and the transformer?

gio
Contributor
Forum|alt.badge.img+15
  • Contributor
  • December 9, 2014
the transformer works as intended...what are you feeding it?

 

post pic of workbench?

david_r
Celebrity
  • December 9, 2014
Hi,

 

 

can confirm that the RasterCellCoercer works as advertised, just make sure that you feed it the right type of features. Use the Inspector or an inspection point to verify.

 

 

Just be aware that the RasterCellCoercer  isn't very quick if you need to process huge amounts of of data...

 

 

David

gio
Contributor
Forum|alt.badge.img+15
  • Contributor
  • December 9, 2014
Yes, to extract values from a raster you can best use PointOnRasterValueExtractor.

 

That is much faster then first using RasateCellCoercer.

 

 

Also you can adress the location of the required cell by using a RasterPropertyExtractor, Rasterpallette generator,RasteSelector and Rasterpallettextractor (latter gives u a list of values of (selected) bands). Latter is ordered by a cellsequencenr.

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