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i have a 70gb national dataset. I want to extract a clip of this data based on a predefined polygon. This is fine, but it takes 7 hours to read the dataset in before carrying out the extraction, and as i only need a small area of this data, is there a way to only read in the area of data i need to extract?

 

 

Thanks in advance.
what type and storage is it?
Hi,

 

 

if your 7GB dataset has a spatial index, try something like this:

 

  • Read the clipper polygon
  • Bufferer to extend the clipper somewhat
  • BoundingBoxReplacer
  • CoordinateExtractor to get lower left and upper right corner
  • Pass the corner values to workspace 2 (WorkspaceRunner)
Workspace 2
  • For the reader, publish the parameters Maximum / Minimum X/Y. These values will be populated with the bounding box corners from the first workspace
  • Do the clipping
Workspace 2 will then only read the features that intersect (loosely) with the clipping polygon. For data formats with a spatial index, this will be done on the database side, which in general is much quicker.

 

 

David
Hi,

 

 

You can simply inspect the polygon, the bounding box coords will be present in the feature information window, apply them to the reader's bounding box coordinates.

 

 

You can also read the polygon and pass it to the FeatureReader, assign the corresponding spatial relation in the transformer and it will do the job of opening/exracting the corresponding featres for you.

 

 

Itay

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