[R-sig-Geo] make_EPSG chile

[Mauricio Zambrano-Bigiarini]

On 28/01/13 11:48, Roger Bivand wrote:
> On Mon, 28 Jan 2013, Mauricio Zambrano-Bigiarini wrote:
>
>> On 27/01/13 22:09, Orietta Nicolis wrote:
>>> Dear R users,
>>>
>>>
>>> I'm trying to run the following example with data of Chile, but I didn't
>>> find a EPSG code for this country which could be used in R.
>>>
>> Hi Orietta,
>>
>> AFAIK, in Chile there are two main local projections:
>>
>> PSAD56 / UTM zone 18S, and
>> PSAD56 / UTM zone 19S
>
> But:
>
>> EPSG <- make_EPSG()
>> EPSG[grep("Chile", EPSG$note), 1:2]
> code note
> 450 5360 # SIRGAS-Chile
> 2697 5361 # SIRGAS-Chile / UTM zone 19S
> 2698 5362 # SIRGAS-Chile / UTM zone 18S

I do not get those values:

library(rgdal)
Loading required package: sp
rgdal: version: 0.8-4, (SVN revision 431)
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 1.8.1, released 2011/07/09
Path to GDAL shared files: /usr/share/gdal
GDAL does not use iconv for recoding strings.
Loaded PROJ.4 runtime: Rel. 4.7.1, 23 September 2009, [PJ_VERSION: 470]
Path to PROJ.4 shared files: (autodetected)

EPSG <- make_EPSG()
EPSG[grep("Chile", EPSG$note), 1:2]
[1] code note
<0 rows> (or 0-length row.names)

which is very likely due to the fact I'm using PROJ4 4.7.1 :(

>
> all of which are WGS84 - do we know whether the +ellps in Orietta's data
> is GRS80 or your earlier intl?

She didn't mention it.
I was working in Chile up to 2006, and at that time most of the 
cartography I saw from public institutions (related to water) used intl 
as ellipsoid. However, last December I realized the cartography (related 
to water) used WGS84.

>
> With PROJ.4 4.8.0, we get a later EPSG too, with:
>
>> CRS("+init=epsg:24879")
> CRS arguments:
> +init=epsg:24879 +proj=utm +zone=19 +south +ellps=intl
> +towgs84=-288,175,-376,0,0,0,0 +units=m +no_defs

Thank you very much for this info. I'll try to update my PROJ4.
>
> which can be transformed to WGS84.

I recently used that projection. Then, when I transformed some  features 
to WGS84 for visualizing in Google Earth, all of them were in close 
agreement with GE.

Mauricio
>
> Roger
>
>>
>> which are used depending on the latitude you are working on.
>>
>> For PSAD56_Z19S, you may try:
>>
>> library(sp)
>> psad56.p4s <- CRS("+proj=utm +zone=19 +south +ellps=intl +units=m
>> +no_defs")
>>
>> which is equivalent to use EPSG:24879
>>
>> if you need higher precision, you may need to add the '+towgs84'
>> argument to 'psad56.p4s'
>>
>> Saludos,
>>
>> Mauricio
>>
>> PS,
>> I'm happy to know there are people in Chile using R !
>>
>>
>