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I'm working with data in latitude/longitude grid form in a non-GIS specialised package (MATLAB) and wish to apply spatial filters to it.

As this data contains a broad range of latitudes and is centred on the North Pole, I need to account for the spacing between points changing with latitude. For example, if I wanted to apply a simple Gaussian filter of radius X km, I can't just convert that radius to Y cells and go - there has to be some kind of correction as the filter width in terms of cells will change with latitude.

How do I attack this problem? Something to do with weighting by latitude?

Thanks, and apologies for my ignorance!

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Just to make sure we all understand: could you explain how your grid could be in geographic coordinates (lat-lon) and yet be centered at a pole? Although it's possible for the data to be centered there, as you write, it is not possible for the grid to be centered there: the singularity at 90 degrees latitude is too severe. However, because you envision merely adjusting a spatial filter, it sounds like your grid really is centered at a pole. That would imply it is actually in projected coordinates and not really in lat-lon. –  whuber May 22 '13 at 17:01
    
@whuber Sorry, that was ill-put: what I meant was the region I'm interested in is centred on the pole (60-90N to be precise). The data is indeed in lat-lon format. –  user18395 May 23 '13 at 11:41
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