Euclidean Distance in Global Datasets

Anonymous User — Fri, 07 Feb 2014 08:02:39 GMT

Original User: tonalca6864

Hi,

I need to do some euclidean distance on a global scale. I find that there is no a natural continuation at the edges due to the Maximum distance option set to default. I've tried with different values always with the same output.

I wonder if someone can suggest a way round this so I can get a continuous raster dataset instead of a sharp differentiation at the edges.

Please see images attached.

Many thanks

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Re: Euclidean Distance in Global Datasets

Anonymous User — Thu, 13 Feb 2014 00:41:07 GMT

Original User: swalbridge

The Euclidean Distance tool isn't geodesic aware, and assumes that the analysis is being performed Cartesian space (i.e. there's no relationship between -180 and 180). There are a few ways to fix this, perhaps the simplest is to use the tools within Data Management > Projections and Transformations > Raster, in particular Shift, to create a version which spans 0-360 degrees, centered on the -180/180 anti-meridian. From there, you should be able to perform a second Euclidean distance calculation and get more sensible results, then merge those two results back together.

But probably better than just doing this is to use a projected space for your analysis -- in unprojected space, measurements of distance vary both by latitude and longitude, so particularly as you head to the poles, the distance of one cell shifts pretty dramatically. A couple of ways of dealing with this include rescaling distances by how far they are from the equator, or using a projected space for your calculations. Using a projection is probably your best bet if you need precision in the answer.

cheers,
Shaun

topic Euclidean Distance in Global Datasets in Data Management Questions

Euclidean Distance in Global Datasets

Re: Euclidean Distance in Global Datasets