[R-sig-Geo] units is semivariograms in GeoR

[Roger Bivand]

On Fri, 18 Nov 2011, carolina monmany wrote:

> Hi,
>
> As suggested, I am transforming my data from Sapper Hill 1943 /
> UTM_Zone_20S to WGS84  /UTM_Zone_20S to run variograms of my plots that

Your input data is almost certainly not what you think. It does seem to be 
in geographical coordinates. See:

http://spatialreference.org/ref/epsg/4292/

and perhaps use:

CRS("+proj=longlat +ellps=intl +towgs84=-355,21,72,0,0,0,0 +no_defs")

or

CRS("+init=epsg:4292")

instead. Your target is probably:

CRS("+init=epsg:29220")

Roger

> have the x axis in meters.  I get the following error message and I need
> some hint of what is going on. The SpatialPointsDataFrame has 6816
> points. Thanks.
>
>> tuc1pro3.50.utm <- spTransform(tuc1pro3.50frm, CRS("+proj=utm +zone=20
> +south +ellps=WGS84 +datum=WGS84 +units=m"))
>
> non finite transformation detected:
>        x         y
> -65.29769 -26.39063       Inf       Inf
> Error in spTransform(xSP, CRSobj) : failure in points 1
> In addition: Warning message:
> In spTransform(xSP, CRSobj) : 6816 projected point(s) not finite
>
>
>
> 2011/11/16 Ben Madin <lists at remoteinformation.com.au>
>
>> You will need to transform (re-project) your data into a suitable
>> coordinate system - use the sptransform() function in the rgdal package, or
>> look at p 64 in the ASDAR book.
>>
>> depending on where you data is and how large an area it covers will
>> influence your choice of coordinate reference system, but you might get
>> away with a UTM grid 19 North for Puerto Rico - have a look here :
>>
>> http://spatialreference.org/ref/epsg/32619/
>>
>> cheers
>>
>> Ben
>>
>>
>> On 16/11/2011, at 11:42 PM, carolina monmany wrote:
>>
>>> Sorry. My problem is that I want the units in the x axis to be in meters
>>> but they are in degrees. How can I make R read the projected coordinate
>>> system, which is in meters, and not the geographic one?
>>>
>>> Thanks!
>>>
>>> 2011/11/16 Paul Hiemstra <paul.hiemstra at knmi.nl>
>>>
>>>> Hi,
>>>>
>>>> This is mail is a bit on the short side :), so please try and be more
>>>> complete next time. I think what you want to know is what the units are
>>>> in a semi-variogram. For the y-axis, they are the unit of the variable
>>>> of interest squared. So if the variable is m/s, than the semi-variogram
>>>> has units (m/s)^2. For the x-axis they are most probably the distance
>>>> unit in which the coordinate system of your data set is, e.g. kilometer.
>>>>
>>>> hope this helps,
>>>> Paul
>>>>
>>>> On 11/16/2011 03:08 PM, carolina monmany wrote:
>>>>
>>>> --
>>>> Paul Hiemstra, Ph.D.
>>>> Global Climate Division
>>>> Royal Netherlands Meteorological Institute (KNMI)
>>>> Wilhelminalaan 10 | 3732 GK | De Bilt | Kamer B 3.39
>>>> P.O. Box 201 | 3730 AE | De Bilt
>>>> tel: +31 30 2206 494
>>>>
>>>> http://intamap.geo.uu.nl/~paul
>>>> http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770
>>>>
>>>>
>>>
>>>
>>> --
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>>
>
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no