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I have a 5km polygon grid of an area which is not a standard square/rectangle, it is in fact a rough ovoid made up of around 500 5km2 cells.

What I want to do, eventually, is have a 100m polygon grid covering the entire area that is currently represented by the ovoid(ish) 5km grid - about 1.25 million cells.

The caveat is that the 100m polygons should be linked to a 'parent' 1km grid square: i.e. you have 12,500 1km cells with a given ID (1KM_ID) and then the 100m cells are given an ID too (100M_ID) which goes from 1 to 100 for each 1km cell.

Using Create Fishnet will create 1km cells based on the bounding box of the 5km cell ovoid, which will greatly increase processing time, i just want the fishnet based on the cells that exist. Same applies for then creating 100m cells from the 1km cells.

This can be done really nicely in FME but for some reason there are processing issues and duplicates are created around the edge of each 1km cell, messing the whole thing up. Any ideas for AcrMap?

  • Have you run a test to create your 1.25 million cells (I think you may be surprised at how quick it is) and then to Select Layer By Location them with your other feature class? – PolyGeo Apr 23 '14 at 9:58
  • What about using the Grid Index Features tool with the 'Generate Polygon Grid that intersects input feature layers' option checked? – GISGe Apr 23 '14 at 10:09
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    @GISGe I think you should propose Grid Index Features as an Answer - it will probably get my upvote although the need to preserve attributes may negate that. – PolyGeo Apr 23 '14 at 10:14
  • Would you be able to describe your current process for assigning IDs to your 100m cells, please? I suspect that wrapping that with Create Fishnet and Select Layer By Location will be quite straightforward and performant. – PolyGeo Apr 23 '14 at 10:20
  • Hi PolyGeo, as current the IDs for all differently sized grids are all created in FME and simply 'carried through' to the next resolution but due to a geometry glitch in FME, i can't use it. This is just a test area, the final shapefiles will be far too large to use the extent then select by location. – Sam Apr 23 '14 at 10:39
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The Grid Index Features tool can be used to create a grid above features and there is an option to only create cells for intersecting features, not for the square extent.

If you need to join the attributes from the 5 km cells, use Spatial Join with 'HAVE_THEIR_CENTER_IN' as Match Option.

Then to calculate the incremental ID for each cell within a 5 km cell, I would use whether Python and an UpdateCursor, or ModelBuilder with an iterator and this expression in a Calculate Field.

This method can probably be improved or simplified but it should do what you want.

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