[GRASS-user] Interpolating rainfall data across area from points

[Markus Metz]

On Tue, Sep 25, 2018 at 2:06 PM Thomas Adams <tea3rd at gmail.com> wrote:
>
> Hello all,
>
> I think there is sufficient evidence to recommend using elevation as a
secondary variable for spatial interpolation of precipitation

as an alternative to kriging, TPS interpolation also allows to use
covariables, e.g. with v.surf.tps or r.resamp.tps (both are addons)

Markus M

> using, for instance, Universal Kriging or spatial drift, or a method such
as PRISM in the USA (http://www.prism.oregonstate.edu/) -- PRISM estimates
are used widely in the US by the National Weather Service and others. See:
>
>
ftp://140.115.123.47/download/%A6h%C5%DC%B6q%A6a%BD%E8%B2%CE%ADp%BE%C7/01_Geostatistical%20approaches%20for%20incorporating%20elevation%20into%20the%20spatial%20interpolation%20of%20rainfall.pdf
>
> https://www.sciencedirect.com/science/article/pii/S0022169418303548
>
> https://www.hydrol-earth-syst-sci.net/10/197/2006/hess-10-197-2006.pdf
>
> But, there is this, e.g., which supports Micha's statement:
>
>
ftp://140.115.123.47/download/%A6h%C5%DC%B6q%A6a%BD%E8%B2%CE%ADp%BE%C7/01_Geostatistical%20approaches%20for%20incorporating%20elevation%20into%20the%20spatial%20interpolation%20of%20rainfall.pdf
>
> Best,
> Tom
>
> On Mon, Sep 24, 2018 at 2:19 PM Micha Silver <tsvibar at gmail.com> wrote:
>>
>> Hi Rich
>>
>>
>> On 09/24/2018 06:32 PM, Rich Shepard wrote:
>>
>>   I want to determine whether GRASS or R is best suited to
>> interpolating/extrapolating annual mean precipitation data from 58
reporting
>> stations (unevenly distributed within the county) across the county. Some
>> flavor of kriging would be applied to these data to illustrate a general
>> long-term pattern of rainfall.
>>
>>   Some years ago there was both a static display of a chemical
constituent
>> in a river reach, a "heat map", (and an automation of temporal changes,
if I
>> correctly recall) and I'm not finding this in the web site galleries.
>>
>>   While elevation could be included as an explanatory variable using
>> regression kriging my purpose is to illustrate county-wide mean annual
rainfall
>> distribution over a 13 year period, not to interpolate values for
specific,
>> unsampled locations.
>>
>>   Please provide some thoughts on the work flow to do this within GRASS.
I'm
>> digging into the gstat docs to get a sense of how to do this within R
(and I
>> have the rgrass7 package working well; it imported the GRASS county
boundary
>> map which I converted to a SpatialPolygonDataFrame.)
>>
>>
>> The guidelines that I follow include:
>>
>> Rainfall interpolation (of any kind) should be done only for long time
periods = at least a full season. since you are looking at 13 years of data
then this requirement is fulfilled.
>> The rules of thumb for "how many points" for kriging interpolation
usually says > 30. So again you are fine.
>> The GRASS modules offer only ordinary kriging AFAIK, which might be
appropriate in this case. But if you want to use Kriging with External
Drift with the elevation as the secondary "trend" variable, I think you'll
need to go with with R. Having said that, I think that "the jury is still
out" on whether elevation improves the interpolation or not.
>>
>> Regards, Micha
>>
>>
>> Rich
>>
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>>
>>
>> --
>> Micha Silver
>> Ben Gurion Univ.
>> Sde Boker, Remote Sensing Lab
>> cell: +972-523-665918
>>
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>
>
>
> --
> Thomas E Adams, III
> 1724 Sage Lane
> Blacksburg, VA 24060
> tea3rd at gmail.com (personal)
> tea at terrapredictions.org (work)
>
> 1 (513) 739-9512 (cell)
>
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