Hello
There is a very small change betwwen 2154 and 102110
+towgs84=0,0,0,0,0,0,0
If I use the small example:
library(sp)
library(rgdal)
xlla=700000
ylla=6500000
ncolsa=1000
nrowsa=1000
cellsizea=1
tableau <- data.frame(IDENT = 1, ncols = 1000, row.names = 1)
crds <- cbind(x=c(xlla,xlla+ncolsa*cellsizea, xlla+ncolsa*cellsizea,
xlla, xlla), y=c(ylla, ylla, ylla+nrowsa*cellsizea,
ylla+nrowsa*cellsizea, ylla))
Pa <- Polygon (crds)
Psa <- Polygons (list ( Pa ), 1)
pola <- SpatialPolygons (list ( Psa ), proj4string=CRS("+init=epsg:2154"))
SPDFa <- SpatialPolygonsDataFrame(pola, tableau)
print(SPDFa)
writeOGR(SPDFa, dsn="C:\\ajeter",layer="toto",driver="ESRI
Shapefile",overwrite_layer=TRUE)
xxx <- readOGR(dsn="C:\\ajeter",layer="toto")
print(xxx)
For SPDFa: there is this projection:
Slot "proj4string":
CRS arguments:
+init=epsg:2154 +proj=lcc +lat_1=49 +lat_2=44 +lat_0=46.5 +lon_0=3 +x_0=700000
+y_0=6600000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
And for xxx there is this projection:
Slot "proj4string":
CRS arguments:
+proj=lcc +lat_1=49 +lat_2=44 +lat_0=46.5 +lon_0=3 +x_0=700000 +y_0=6600000
+ellps=GRS80 +units=m +no_defs
I don't see the same argument in the CRS, and in 2154, there is this small part:
+towgs84=0,0,0,0,0,0,0
I think there is no big problem of shift but when I create a file and I put it
in other GIS (Qgis), it is not recognize as 2154.
Last comment, with the shapefile, the prj don't give the same things betwwen
2154 and 102110
2154 PROJCS["Lambert_Conformal_Conic",GEOGCS["GCS_GRS 1980(IUGG,
1980)",DATUM["D_unknown",SPHEROID["GRS80",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["standard_parallel_1",49],PARAMETER["standard_parallel_2",44],PARAMETER["latitude_of_origin",46.5],PARAMETER["central_meridian",3],PARAMETER["false_easting",700000],PARAMETER["false_northing",6600000],UNIT["Meter",1]]
102110
PROJCS["RGF93_Lambert_93",GEOGCS["GCS_RGF93",DATUM["D_RGF_1993",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["standard_parallel_1",49],PARAMETER["standard_parallel_2",44],PARAMETER["latitude_of_origin",46.5],PARAMETER["central_meridian",3],PARAMETER["false_easting",700000],PARAMETER["false_northing",6600000],UNIT["Meter",1]]
GCS_RGF93 don't appear in R!
Thanks for your help
Frédéric
*Frédéric Pons *
*Expert hydraulique sur les inondations et aléas côtiers
**DREC/Service Risques Inondations Littoraux et Hydraulique **- Tél.:
(33)4 42 24 76 68 *
*Direction Territoriale Méditerranée
*
Centre d’études et d’expertise sur les risques, l’environnement, la
mobilité et l’aménagement
www.cerema.fr <http://www.cerema.fr>
Le 22/09/2015 16:44, > Hodgess, Erin (par Internet) a écrit :
Hello!
I ran through your example, and brought the OGR file back into R via
the readOGR function.
> xxx <- readOGR(dsn="C:\\ajeter",layer="toto")
OGR data source with driver: ESRI Shapefile
Source: "C:\ajeter", layer: "toto"
with 1 features
It has 2 fields
> str(xxx)
Formal class 'SpatialPolygonsDataFrame' [package "sp"] with 5 slots
..@ data :'data.frame': 1 obs. of 2 variables:
.. ..$ IDENT: num 1
.. ..$ ncols: num 1000
..@ polygons :List of 1
.. ..$ :Formal class 'Polygons' [package "sp"] with 5 slots
.. .. .. ..@ Polygons :List of 1
.. .. .. .. ..$ :Formal class 'Polygon' [package "sp"] with 5 slots
.. .. .. .. .. .. ..@ labpt : num [1:2] 700500 6500500
.. .. .. .. .. .. ..@ area : num 1e+06
.. .. .. .. .. .. ..@ hole : logi FALSE
.. .. .. .. .. .. ..@ ringDir: int 1
.. .. .. .. .. .. ..@ coords : num [1:5, 1:2] 700000 700000 701000
701000 700000 ...
.. .. .. ..@ plotOrder: int 1
.. .. .. ..@ labpt : num [1:2] 700500 6500500
.. .. .. ..@ ID : chr "0"
.. .. .. ..@ area : num 1e+06
..@ plotOrder : int 1
..@ bbox : num [1:2, 1:2] 700000 6500000 701000 6501000
.. ..- attr(*, "dimnames")=List of 2
.. .. ..$ : chr [1:2] "x" "y"
.. .. ..$ : chr [1:2] "min" "max"
..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
.. .. ..@ projargs: chr "+proj=lcc +lat_1=49 +lat_2=44 +lat_0=46.5
+lon_0=3 +x_0=700000 +y_0=6600000 +ellps=GRS80 +units=m +no_defs"
>
If you put that big @projagrs into google.com, this is what you get:
Proj4js.defs["EPSG:2154"] = "+proj=lcc +lat_1=49 +lat_2=44 +lat_0=46.5 +lon_0=3
+x_0=700000 +y_0=6600000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs";
Is that what you want, please?
Thanks,
Erin
------------------------------------------------------------------------
*From:* R-sig-Geo [r-sig-geo-boun...@r-project.org] on behalf of PONS
Frederic - CEREMA/DTerMed/DREC/SRILH [frederic.p...@cerema.fr]
*Sent:* Tuesday, September 22, 2015 9:25 AM
*To:* r-sig-geo@r-project.org
*Subject:* [R-sig-Geo] Problem in EPSG 2154 => 102110
Dear R-users,
I have a problem when I create a spatialpolygondataframe
I want to have an EPSG 2154 but after the export the epsg is 102110.
It seems to be the "same" CRS but it is not what I want.
A small example to help me
Best regards
xlla=700000
ylla=6500000
ncolsa=1000
nrowsa=1000
cellsizea=1
tableau <- data.frame(IDENT = 1, ncols = 1000, row.names = 1)
crds <- cbind(x=c(xlla,xlla+ncolsa*cellsizea, xlla+ncolsa*cellsizea,
xlla, xlla), y=c(ylla, ylla, ylla+nrowsa*cellsizea,
ylla+nrowsa*cellsizea, ylla))
Pa <- Polygon (crds)
Psa <- Polygons (list ( Pa ), 1)
pola <- SpatialPolygons (list ( Psa ), proj4string=CRS("+init=epsg:2154"))
SPDFa <- SpatialPolygonsDataFrame(pola, tableau)
writeOGR(SPDFa, dsn="C:\\ajeter",layer="toto",driver="ESRI
Shapefile",overwrite_layer=TRUE)
*Frédéric Pons *
*Expert hydraulique sur les inondations et aléas côtiers
**DREC/Service Risques Inondations Littoraux et Hydraulique **- Tél.:
(33)4 42 24 76 68 *
*Direction Territoriale Méditerranée
*
Centre d’études et d’expertise sur les risques, l’environnement, la
mobilité et l’aménagement
www.cerema.fr <http://www.cerema.fr>
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