[R-sig-Geo] [DKIM] Re: FW: Spatial sampling design using information more than spatial coordinates [SEC=UNCLASSIFIED]

Thu Apr 9 03:49:39 CEST 2015

Hi Tom 2  :-),

To be specific,  we need to do the spatial stratification first and need to stratify the survey area into n equal-area strata. The function stratify with equalArea in spcosa meets this need well.

And then within each stratum, we need to do further stratification based on a raster layer of 'elevation' that is a continuous layer and needs to be converted into 3 zones. We need to sample m samples within each stratum and these samples need to be evenly distributed within each zone. That is we need to use the area of each zone as a weight to decide how many samples should be allocated to each zone. And then do randomly sampling within each zone.

A further challenge is that they plan to sample 1 to 4 samples a day during 25 days, so we need to provide four designs with 25, 50, 75 and 100 samples respectively. The samples of the design with smaller sample size need to be nested in the samples of the design with larger sample size for operational reasons as the survey needs to meet other tasks and also to accommodate weather conditions at sea. Now you know the 'elevation' is bathymetry that is the depth of water. We plan to let n = 25, and m = 1 to 4. But it is hard to stratify if a stratum contains 3 zones and m <3.

Hope this clarify things a bit. Any further suggestions are appreciated!

Jin

-----Original Message-----
From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Tom Philippi
Sent: Thursday, 9 April 2015 9:32 AM
To: Tomislav Hengl
Cc: r-sig-geo
Subject: [DKIM] Re: [R-sig-Geo] FW: Spatial sampling design using information more than spatial coordinates [SEC=UNCLASSIFIED]

Jin--

Could you provide more information on what the needs of your client are that cannot be handled by either stratification or unequal probability based on your one or more covariates in spsurvey?  Also, is your sample frame points, polygons, or raster?  I assume your covariates are raster (e.g., DEM for elevation) and polygons (most soil maps)?

Tom 2

On Wed, Apr 8, 2015 at 6:39 AM, Tomislav Hengl <hengl at spatial-analyst.net<mailto:hengl at spatial-analyst.net>>

wrote:

>

> The "clhs" package (http://cran.r-project.org/web/packages/clhs/) has

> some functionality for latin-hypercube sampling hence it is suitable

> for your case. Here are some code examples: http://gsif.isric.org/doku.

> php?id=wiki:tutorial_eberg#testing_the_feature_space_coverage

>

> I have also recently (experimentally) implemented a function to test

> 'efficiency of any sampling plan' which looks at both geographical

> space and feature space representation: http://gsif.r-forge.r-project.

> org/spsample.prob.html

> If you discover a bug or some 'strange behavior', please let me know.

>

> HTH,

>

> T. (Tom) Hengl

> Researcher @ ISRIC - World Soil Information Team member Africa Soil

> Information Services http://africasoils.net

> Url: http://www.wageningenur.nl/en/Persons/dr.-T-Tom-Hengl.htm

> Network: http://profiles.google.com/tom.hengl

> Publications: http://scholar.google.com/citations?user=2oYU7S8AAAAJ

>

>

>

> On 8-4-2015 2:24, Jin.Li at ga.gov.au<mailto:Jin.Li at ga.gov.au> wrote:

>

>> Sorry for not ccing to the list!

>>

>> -----Original Message-----

>> From: Li Jin

>> Sent: Tuesday, 7 April 2015 9:36 AM

>> To: 'Roger.Bivand at nhh.no'

>> Subject: RE: [R-sig-Geo] Spatial sampling design using information

>> more than spatial coordinates [SEC=UNCLASSIFIED]

>>

>> Thanks a lot, Roger! Yes, we have looked at spsurvey and it does not

>> meet the needs of our client.

>> Kind regards,

>> Jin

>>

>> -----Original Message-----

>> From: Roger Bivand [mailto:Roger.Bivand at nhh.no]

>> Sent: Friday, 3 April 2015 2:06 AM

>> To: Li Jin

>> Cc: r-sig-geo at r-project.org<mailto:r-sig-geo at r-project.org>

>> Subject: Re: [R-sig-Geo] Spatial sampling design using information

>> more than spatial coordinates [SEC=UNCLASSIFIED]

>>

>> On Thu, 2 Apr 2015, Jin.Li at ga.gov.au<mailto:Jin.Li at ga.gov.au> wrote:

>>

>>  Hi All,

>>>

>>> I need to consider both spatial information and another variable (e.g.

>>> elevation, soil type) in a sampling design. It seems the available

>>> libraries (e.g. sp and spcosa) in R for spatial sampling design are

>>> unable to handle it. Please correct me if I am wrong. Before I start

>>> to develop my own function for it, I would like to confirm if I have

>>> missed some other functions that are available for it in R.  Any

>>> suggestions and advice? Thanks in advance!

>>>

>>

>> Have you looked at spsurvey? It may not provide what you need, but

>> checking it would probably help you see whether there is anything

>> meeting your needs. Otherwise you might need to stratify first on your covariates.

>>

>> Roger

>>

>>

>>> Regards,

>>> Jin

>>>

>>> Jin Li, PhD

>>> Spatial Modeller/Computational Statistician  |  National Earth and

>>> Marine Observations Group Environmental Geoscience Division  |

>>> GEOSCIENCE AUSTRALIA ______________________________

>>> ______________________________

>>> Phone:  +61 2 6249 9899    Fax:  +61 2 6249 9999

>>> Email:  Jin.Li at ga.gov.au<mailto:Jin.Li at ga.gov.au<mailto:Jin.Li at ga.gov.au%3cmailto:Jin.Li at ga.gov.au>>    Web:  www.ga.gov.au<http://www.ga.gov.au>

>>> <http://www.ga.gov.au/>

>>> Cnr Jerrabomberra Avenue and Hindmarsh Drive Symonston ACT GPO Box

>>> 378 Canberra ACT 2601 Australia Applying geoscience to Australia's

>>> most important challenges

>>>

>>>

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>> --

>> Roger Bivand

>> Department of Economics, Norwegian School of Economics, Helleveien

>> 30,

>> N-5045 Bergen, Norway.

>> voice: +47 55 95 93 55; fax +47 55 95 91 00

>> e-mail: Roger.Bivand at nhh.no<mailto:Roger.Bivand at nhh.no>

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