[R-sig-Geo] Different result from sptransform() and ptransform()

[Agustin Lobo]

Right, grid1km is the polygon object from whence cents comes from and
I copied the wrong line.
Sorry for the confusion.
The part with ptransform() should be:

> a <- ptransform(data = coordinates(cents), src.proj = CRSargs(CRS("+init=epsg:3035")), dst.proj = CRSargs(CRS("+init=epsg:4326")))
> coordinates(cents)[1:3,]
           X       Y
[1,] 3603500 2167500
[2,] 3604500 2167500
[3,] 3605500 2167500
> a[1:3,]
           [,1]      [,2] [,3]
[1,] 0.02295650 0.7372194    0
[2,] 0.02316621 0.7372375    0
[3,] 0.02337593 0.7372556    0

Agus

2012/1/28 Rainer Hurling <rhurlin at gwdg.de>:
> On 28.01.2012 19:30 (UTC+1), Agustin Lobo wrote:
>>
>> Hi!
>> I'm reprojecting and get different results from sptransform() than
>> from ptransform():
>> (objec cents in https://sites.google.com/site/filestemp2/home/cents.rda)
>>
>>> str(cents,max.level=2)
>>
>> Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
>>   ..@ data       :'data.frame':        234 obs. of  4 variables:
>>   ..@ coords.nrs : num(0)
>>   ..@ coords     : num [1:234, 1:2] 3603500 3604500 3605500 3606500
>> 3607500 ...
>>   .. ..- attr(*, "dimnames")=List of 2
>>   ..@ bbox       : num [1:2, 1:2] 3603500 2155500 3620500 2167500
>>   .. ..- attr(*, "dimnames")=List of 2
>>   ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
>>
>>> proj4string(cents)
>>
>> [1] " +init=epsg:3035 +proj=laea +lat_0=52 +lon_0=10 +x_0=4321000
>> +y_0=3210000 +ellps=GRS80 +units=m +no_defs"
>>>
>>> centslonlat<- spTransform(cents,CRS("+init=epsg:4326"))
>>> coordinates(centslonlat)[1:3,]
>>
>>             X        Y
>> [1,] 1.315311 42.23956
>> [2,] 1.327326 42.24060
>> [3,] 1.339342 42.24163
>>
>>> a<- ptransform(data = as.data.frame(coordinates(grid1km)), src.proj =
>>> CRSargs(CRS("+init=epsg:3035")), dst.proj = CRSargs(CRS("+init=epsg:4326")))
>
>
> Hmm, grid1km is not known here until now?
>
> Greetings,
> Rainer
>
>
>>> coordinates(a)[1:3,]
>>
>>               x         y z
>> [1,] 0.02295650 0.7372194 0
>> [2,] 0.02316621 0.7372375 0
>> [3,] 0.02337593 0.7372556 0
>>
>> The correct results are those from sptransform(), but I would like to
>> know what I'm doing wrong with ptansform()
>>
>> Thanks
>>
>> Agus
>
>