[GRASS-user] cross validation v.surf.rst

GRASS GRASS user
1

Hi,
I'm using the cross validation procedure of v.surf.rst

I have around 250 points on a region of 100 square kilometers and I'm
working in a region having 10 meters resolution

When I run a cross validation using v.surf.rst I regularly get the cvdev
file but what it seems strange is that it takes only few seconds to run
on a normal PC with a i7 core.

I suppose that it would had to run the interpolation 250 times but it
seems it runs only one time.

Is this normal?

many thanks

Ivan

2

Hi,

···

On Tue, Nov 4, 2014 at 3:58 AM, Ivan Marchesini <ivan.marchesini@gmail.com> wrote:

Hi,
I’m using the cross validation procedure of v.surf.rst

I have around 250 points on a region of 100 square kilometers and I’m
working in a region having 10 meters resolution

When I run a cross validation using v.surf.rst I regularly get the cvdev
file but what it seems strange is that it takes only few seconds to run
on a normal PC with a i7 core.

I suppose that it would had to run the interpolation 250 times but it
seems it runs only one time.

Is this normal?

Yes, first, you have only 250 points, that’s not too many. Then during the cross validation, only the value in the particular point is computed, not in every cell of the raster. If you would use a recent version (couple of weeks ago) of grass 7, there should be even some speedup in storing attribute values in database.

Best,
Anna

many thanks

Ivan

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