Augustin
just quick and dirty if you run gdalinfo("geo_em.d01.nc") your are
getting the information about the corner coordinates the subdatasets and
so on. Together with Dominiks suggestion you can do something like this:
library(gdalUtils)
library(raster)
Sys.setenv(GDAL_NETCDF_BOTTOMUP="YES")
wrffake<- "+proj=longlat +ellps=sphere +a=6370000 +b=6370000 +units=m
+no_defs"
x<-gdal_translate('NETCDF:"geo_em.d01.nc":LANDMASK', 'landmask.tif',
of="GTiff",
ot="Byte",
output_Raster=TRUE,
verbose=TRUE)
wrfExt<-extent(-151.29639,-48.703613,12.355667,50.26619)
extent(x) <- extent(wrfExt)
projection(x) <- wrffake
plot(x)
Some remarks:
(1) I just took the first pair of coordinates as derived from
gdalinfo("geo_em.d01.nc")
you will find 4 different coordinate pairs (i did not proof which one is
right
The data is staggered (as outlined by Dominik) So some of the corner
coordinates belongs to the staggered data and the others coordinates to
the unstaggered ones. You will find them marked
If you have installed the netcdf libs you easily can use ncview
geo_em.d01.nc or ncdump -h geo_em.d01.nc to view the data or get more
information of the header.
Hope this helps
cheers Chris
Am 23.02.2016 um 21:11 schrieb Agus Camacho:
Thanks for that Dominik,
Giving that projection to either the locations, the raster layer generated
from the .nc file, or both, still did not work. I keep having locations
that should be on land falling far on the sea. Might this be a problem
derived from using raster with a file whose original grid distances are not
constant?
Here is a link with the original file which has the original coordinate
data.
https://www.dropbox.com/s/qpt5twtunhy3x3x/geo_em.d01.nc?dl=0
2016-02-23 12:07 GMT-07:00 Dominik Schneider <dominik.schnei...@colorado.edu
:
This looks like WRF <http://www.wrf-model.org/index.php> data. I just
dealt with this.
The data is on a sphere as opposed to WGS84 so you need +ellps=sphere
+a=6370000 +b=6370000 +units=m
+proj=lcc which is usually what wrf is run with.
The tricky part is:
+lat_1=25.0 +lat_2=45.0 +lat_0=38.0 +lon_0=-100.0
because every WRF run is different (the WRF Preprocessing System optimizes
the projection for the domain).
and then there is probably no shift so you need(?) +x_0=0 +y_0=0
This gives:
+proj=lcc +lat_1=25.0 +lat_2=45.0 +lat_0=38.0 +lon_0=-100.0 +ellps=sphere
+a=6370000 +b=6370000 +units=m +no_defs
But, wrf users like to give out lat and long so you need to assign it:
+proj=longlat +ellps=sphere +a=6370000 +b=6370000 +units=m +no_defs
and then reproject the lat/long to lcc coordinates using this string:
+proj=lcc +lat_1=25.0 +lat_2=45.0 +lat_0=38.0 +lon_0=-100.0 +ellps=sphere
+a=6370000 +b=6370000 +units=m +no_defs
One word of caution, make sure you received the correct coordinates. Some
variables are run cell center while some are run at cell edge. It looks
like from your .nc file it was made by your collaborator so I assume they
are right.
That said, another word of caution, I found that the XLAT and XLONG
variables from WRF output aren't very precise. There is a "geogrid" file
from the preprocessing system that has the domain corners, resolution, nrow
and ncol from which you can make a better grid using the native projection
system (in my case it was a 4km grid). I suggest you try to get those.
I hope this helps... I have to run but wanted to save people too much head
scratching. I can get you running with more help tonight if you need.
Dominik
On Tue, Feb 23, 2016 at 11:27 AM, Agus Camacho <agus.cama...@gmail.com>
wrote:
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 <mdsum...@gmail.com>:
On Tue, 23 Feb 2016 at 20:09 Roger Bivand <roger.biv...@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
fr...@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-boun...@r-project.org] On
Behalf Of
Agus Camacho
Sent: 22. februar 2016 19:20
To: t...@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_...@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@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.biv...@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@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@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]]
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
