Projection error in spline with barriers using 0-360deg data

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11-20-2013 10:29 AM
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New Contributor
I want to create an interpolated raster with spline with barriers from projected global climate data models.

I am working with model builder.

I add the file as *.nc, then create a nc to xy table, then create an event layer, and then interpolate (0.04 cell size to match observed data) with a shapefile of the world's continents as barrier. The problem is the climate data is in a 0-360 positive long grid.

So far I have tried:

1. When I use the continent shapefile (Esri's continent file on WSG84), the splined raster comes out weird because the shapefile is in a different projection (only half of the interpolation uses the barrier).

2. I tried reprojecting the shapefile into Plate Carre (and then again into Plate carre, following this forum post http://forums.esri.com/thread.asp?c=93&f=982&t=88435), same result as #1.

3. I then tried to project the climate data event layer to WSG84; I get a new error, "the raster has too many cells" , even if I change the cell size the result is the same.

The natural neighbors and IDW interpolations work fine, but I need spline with barriers.

Thanks!
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Esri Regular Contributor
None of the current interpolation tools do "round the world" interpolation. I.e. the search neighborhood ends at 0 and at 360. Think of it as a rectangle 0 to 360 and -90 to +90. The points on the far left, circa 0, are not considered neighbors of the points on the far right, circa 360. Also, the Arctic Circle is a rectangle! Also, a cell size of 0.04 at the equator and a the poles, what does it represent?

If you make the cell size too small then you might encounter the SplineWithBarriers size limit (16500; 16500 columns and rows). However, a cellsize of 0.04 degrees only yields a raster with 9028 columns and 4358 rows.

To do this type of interpolation you'll need to interpolate in blocks and Mosaic the output. Also best to work in projected coordinates and not in Geographic coordinates.

-Steve
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