[R-sig-Geo] adapting spatial points and wrld_smpl to a reference system implicit in a .nc file

Tue Feb 23 10:08:44 CET 2016

On Tue, 23 Feb 2016, Alex Mandel wrote:

> I made an attempt at it too. Investigating the original data, I'm not
> sure that the projection information supplied is correct for the data
> linked. When I load up the data in a unprojected space, the coordinates
> don't look at all similar to any Lambert projected data I have, they
> actually look like Lat/Lon in some unprojected coordinate system,
> perhaps a different spheroid than expected.

Does anyone have a link to the original data? Is is possible that this is 
the General Oblique Transformation used by modellers - that is something 
that feels like longlat but is recentred and oblique? Example at the very 
end of my GEOSTAT talk last year (slides 81-83):

http://geostat-course.org/system/files/geostat_talk_150817.pdf

Roger

>
> -Alex
>
> On 02/22/2016 10:17 PM, Frede Aakmann Tøgersen wrote:
>> Hi
>> 
>> I tried to make it work but I had to give up. I wanted to reproject the Lamberth conformal conic coordinates to long-lat but it didn't work.
>> 
>> Perhaps someone can see what I did wrong. Here is what I did (data in R binary format and figure in png format both attached):
>> 
>> library(raster)
>> library(maptools)
>> data(wrld_simpl)
>> 
>> r <- raster("raster.grd")
>> projection(r)
>> ## > NA
>> 
>> uro <- read.table("clean urosaurus records.csv", h = TRUE, sep = ",")
>> coordinates(uro) <- ~lon+lat
>> 
>> ## Set projections for the 3 data sets
>> 
>> ## Lamberth's confocal conic projection with given parameters
>> crs(r) <- "+proj=lcc +lat_0=38.0 +lon_0=-100 +lat_1=25.0 +lat_2=45.0 +ellps=WGS84"
>> projection(r)
>> 
>> ## Assume that lon, lat are geographical coordinates (degrees decimal)
>> proj4string(uro) <- CRS("+proj=longlat +datum=WGS84")
>> 
>> ## wrld_simpl is in geographical coordinates
>> proj4string(wrld_simpl)
>> 
>> ## Make figure in png format
>> ## Of course plotting data with 2 different projections will give
>> ## some distortions
>> pdf("uro.png")
>> 
>> plot(r)
>> points(uro)
>> plot(wrld_simpl, add = TRUE) # World will be clipped to extent of 'r'
>> 
>> dev.off()
>> 
>> extent(r)
>> ## class       : Extent 
>> ## xmin        : -131.4368 
>> ## xmax        : -68.56323 
>> ## ymin        : 12.35567 
>> ## ymax        : 50.26619 
>> 
>> ## Reproject the raster to long-lat
>> ## This doesn't work (collapsed domain)
>> rp <- projectRaster(r, crs = "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0")
>> 
>> ## Because
>>> extent(rp)
>> ## class       : Extent 
>> ## xmin        : -100.0015 
>> ## xmax        : -99.68557 
>> ## ymin        : 37.70658 
>> ## ymax        : 38.00046 
>> 
>> ## Save data in R binary format
>> save(list = c("r", "uro", "wrld_simpl"), file = "uro.RData")
>> 
>> 
>> Yours sincerely / Med venlig hilsen
>> 
>> Frede Aakmann Tøgersen
>> Specialist, M.Sc., Ph.D.
>> Plant Performance & Modeling
>> 
>> Technology & Service Solutions
>> T +45 9730 5135
>> M +45 2547 6050
>> frtog at vestas.com
>> http://www.vestas.com
>> 
>> Company reg. name: Vestas Wind Systems A/S
>> This e-mail is subject to our e-mail disclaimer statement.
>> Please refer to www.vestas.com/legal/notice
>> If you have received this e-mail in error please contact the sender. 
>> 
>> 
>> 
>> -----Original Message-----
>> From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Agus Camacho
>> Sent: 22. februar 2016 19:20
>> To: tech at wildintellect.com
>> Cc: r-sig-geo
>> Subject: Re: [R-sig-Geo] adapting spatial points and wrld_smpl to a reference system implicit in a .nc file
>> 
>> Thanks Alex, but the locations still fall in the sea when i plot them using
>> your recommended Solution. I looked at the sites you proposed and they have
>> other values for lat_1, lat_0, etc..
>> 
>> 2016-02-22 11:04 GMT-07:00 Alex M <tech_dev at wildintellect.com>:
>> 
>>> On 02/22/2016 09:50 AM, Agus Camacho wrote:
>>>> Dear all,
>>>>
>>>> Im trying to overlap these points:
>>>>
>>> https://www.dropbox.com/s/awdclg4cvsdngej/clean%20urosaurus%20records.csv?dl=0
>>>>
>>>> and a wrld_simpl object:
>>>> library(maptools)
>>>> data(wrld_simpl)
>>>>
>>>> Over this raster layer
>>>>
>>> https://www.dropbox.com/sh/qcw174tgogpnz7s/AAByDc3TeyFe3W4nEqTFix6Oa?dl=0
>>>>
>>>> This rastr comes from a .nc file without a reference system. The author
>>> of
>>>> that .nc file gave me the following data about the .nc.
>>>>
>>>> The projection is *Lambert conformal conic* projection
>>>> CEN_LAT = 38.0
>>>> CEN_LON = -100.0
>>>> TRUELAT1 = 25.
>>>> TRUELAT2 = 45.
>>>>
>>>> However, despite i have gone through many sites in the internet, i cant
>>>> figure it out:
>>>>
>>>> a) if that is all the data i need to set a reference system for my points
>>>> and the wrld_simp object.
>>>>
>>>> b) how to change a typical CRS object with such data
>>>>
>>>> Ex.CRS ("+proj=lcc+lat_0=38.0+lon0_2=-100+ellps=WGS84")
>>>>
>>>> Where do i enter the TRUELAT and CENLAT values?
>>>> Are there any site that explains easily what the fields in the CRS mean
>>> and
>>>> how to change them?
>>>>
>>>> Thanks in advance.
>>>>
>>>
>>> https://github.com/OSGeo/proj.4/wiki/GenParms
>>> https://trac.osgeo.org/proj/wiki/GenParms
>>>
>>> I believe:
>>> +lat_0  = CEN_LAT   Latitude of origin
>>> +lat_1  = TRUELAT1   Latitude of first standard parallel
>>> +lat_2  = TRUELAT2   Latitude of second standard parallel
>>> +lon_0  = CEN_LON   Central meridian
>>>
>>> proj strings are defined by the proj4 libary. It's website listed above
>>> and the associated mailing lists or gis stackexchange would be the
>>> places to get help on it.
>>> https://lists.osgeo.org/mailman/listinfo/metacrs
>>>
>>> It often helps to browse similar projections on
>>> http://spatialreference.org/
>>> http://epsg.io/
>>>
>>> Enjoy,
>>> Alex
>>>
>>>
>> 
>>
>
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-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
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