[GRASS-stats] getLocationProj - writeVECT projection check mismatch

[Paulo van Breugel]

On 12-08-18 15:12, Roger Bivand wrote:
> On Sun, 12 Aug 2018, Paulo van Breugel wrote:
>
>> Dear devs,
>>
>> The function getLocationProj returns an spproj-compliant PROJ.4 
>> string of projection information (using internally /g.proj -jf/). 
>> However, when writing a vector layer to the grass database using the 
>> writeVECT function, it (expects the projection information in the 
>> format returned by /g.proj -g/ (checking the code, this is because it 
>> uses v.in.ogr I guess).
>>
>> For example, if running R from within a grass session with the NC 
>> location: I have a vector layer "klatifolia" in latlong which I 
>> project it to match the projection of the NC location. Next, I write 
>> it to the grass database using writeVECT:
>>
>> proj <- getLocationProj()
>> KLnew <- spTransform(KL, proj)
>> writeVECT(SDF=KLnew[,c(1,2,5)], vname="KLatifolia", driver="SQLite")
>>
>> This results in an error telling that the projection of dataset does 
>> not appear to match current location.
>>
>>        Location PROJ_INFO is:
>>        name: Lambert Conformal Conic
>>        proj: lcc
>>        datum: nad83
>>        a: 6378137.0
>>        es: 0.006694380022900787
>>        lat_1: 36.16666666666666
>>        lat_2: 34.33333333333334
>>        lat_0: 33.75
>>        lon_0: -79
>>        x_0: 609601.22
>>        y_0: 0
>>        no_defs: defined
>>
>>        Dataset PROJ_INFO is:
>>        name: unnamed
>>        ellps: grs80
>>        proj: lcc
>>        lat_1: 36.16666666666666
>>        lat_2: 34.33333333333334
>>        lat_0: 33.75
>>        lon_0: -79
>>        x_0: 609601.22
>>        y_0: 0
>>        towgs84: 0,0,0,0,0,0,0
>>        no_defs: defined
>>
>>        ERROR: datum
>>
>> I can obviously run writeVECT with v.in.ogr_flags="o", but is there a 
>> way that writeVECT can check against the spproj-compliant proj.4 
>> string? Or is this something that should be dealt with at the 
>> v.in.ogr side?
>
> Short answer - after inspecting the two, and checking that they are 
> the same, use v.in.ogr_flags="o".
>
> Long answer: the PROJ migration from 4.* to 5.* and further is 
> shifting things everywhere, so handling in GRASS and sf/rgdal will 
> also change. On the R side, we are waiting for the GDAL barn-raising 
> project (writing C++ classes for PROJ) to complete before considering 
> moving to the pipeline model and possible new representations.
>
> Roger

Hi Roger, thanks for the reply, all clear, I'll keep on using 
v.in.ogr_flags="o".

>
>>
>> Best wishes,
>>
>> Paulo
>>
>>
>> sessionInfo()
>> R version 3.4.4 (2018-03-15)
>> Platform: x86_64-pc-linux-gnu (64-bit)
>> Running under: Ubuntu 18.04.1 LTS
>>
>> Matrix products: default
>> BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
>> LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1
>>
>> locale:
>>  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C LC_TIME=en_US.UTF-8
>>  [4] LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8 
>> LC_MESSAGES=en_US.UTF-8
>>  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C LC_ADDRESS=C
>> [10] LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 
>> LC_IDENTIFICATION=C
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods base
>>
>> other attached packages:
>> [1] ggplot2_3.0.0  mapr_0.4.0     raster_2.6-7   rgrass7_0.1-11 
>> XML_3.98-1.12  maptools_0.9-3
>> [7] sp_1.3-1       rgbif_1.0.2
>>
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>