[R-sig-Geo] adapting spatial points and wrld_smpl to a reference system implicit in a .nc file
Agus Camacho
agus.camacho at gmail.com
Tue Feb 23 19:27:46 CET 2016
Thanks heaps to all for your effort. If I go to another GEOSTAT ill bring
more giant crab this time.
The creator of the .nc file also looked at this webpage:
http://www.pkrc.net/wrf-lambert.html
It seemed like the right proj4 string might be this one:
+proj=lcc +lat_1=25.0 +lat_2=45.0 +lat_0=38.0
+lon_0=-100.0 +a=6370 +b=6370 +towgs84=0,0,0 +no_defs
However this projection also does not allow me to adequately plot the
locations on the raster.
Here is the .nc file. it contains several layers.
https://www.dropbox.com/s/yto3linsgom3zi7/results_us_future_output_none_0.nc?dl=0
2016-02-23 2:25 GMT-07:00 Michael Sumner <mdsumner at gmail.com>:
> On Tue, 23 Feb 2016 at 20:09 Roger Bivand <Roger.Bivand at nhh.no> wrote:
>
> > 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
> >
> >
> For what it is worth, the General Oblique Transformation is not the only
> example - it's very common for modellers to have a mesh that has the
> "mostly-properties" of a projection, but is not actually describable with
> standard transform + affine parameters. The main cases that I've seen are
> polar stereographic, equal area or oblique Mercator. Often they really are
> simple transforms and you can reconstruct without loss, but it's not
> usually possible to tell without exploration. It's an interesting
> dis-connect to see code that builds a mesh with certain properties, then
> only stores longitudes and latitudes - when it could be done with standard
> tools and be stored and used much more efficiently.
>
> (I've seen Lambert Conformal Conic and Lambert Azimuthal Equal Area
> terminology conflated in this context too. )
>
> I'm also interested to explore the original data.
>
> Cheers, Mike.
>
>
>
> > >
> > > -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
> > >>>
> > >>>
> > >>
> > >>
> > >
> > > _______________________________________________
> > > R-sig-Geo mailing list
> > > R-sig-Geo at r-project.org
> > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
> > --
> > Roger Bivand
> > Department of Economics, Norwegian School of Economics,
> > Helleveien 30, N-5045 Bergen, Norway.
> > voice: +47 55 95 93 55; fax +47 55 95 91 00
> > e-mail: Roger.Bivand at nhh.no
> > http://orcid.org/0000-0003-2392-6140
> > https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
> > http://depsy.org/person/434412
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
> --
> Dr. Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> 203 Channel Highway
> Kingston Tasmania 7050 Australia
>
> [[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
--
Agustín Camacho Guerrero.
Doutor em Zoologia.
Laboratório de Herpetologia, Departamento de Zoologia, Instituto de
Biociências, USP.
Rua do Matão, trav. 14, nº 321, Cidade Universitária,
São Paulo - SP, CEP: 05508-090, Brasil.
[[alternative HTML version deleted]]
More information about the R-sig-Geo
mailing list