[R-sig-Geo] adapting spatial points and wrld_smpl to a reference system implicit in a .nc file
tech_dev at wildintellect.com
Tue Feb 23 07:25:59 CET 2016
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.
On 02/22/2016 10:17 PM, Frede Aakmann Tøgersen wrote:
> 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):
> r <- raster("raster.grd")
> ## > 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"
> ## Assume that lon, lat are geographical coordinates (degrees decimal)
> proj4string(uro) <- CRS("+proj=longlat +datum=WGS84")
> ## wrld_simpl is in geographical coordinates
> ## Make figure in png format
> ## Of course plotting data with 2 different projections will give
> ## some distortions
> plot(wrld_simpl, add = TRUE) # World will be clipped to extent of '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
> ## 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
> Company reg. name: Vestas Wind Systems A/S
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> -----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:
>>> and a wrld_simpl object:
>>> Over this raster layer
>>> This rastr comes from a .nc file without a reference system. The author
>>> 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
>>> how to change them?
>>> Thanks in advance.
>> 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.
>> It often helps to browse similar projections on
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