Hello,
A new list member here with a question regarding the display of projected
NetCDF files in R. The initial grids (dimension 349 x 277) cover all of North
America with the following borders:
12.2N;133.5W, 54.5N; 152.9W, 57.3N; 49.4W ,14.3N;65.1W in the Lambert Conformal
Conic Grid. I extracted a smaller grid (our area of interest) which becomes a
64 x 51 matrix for air temperature, longitude and latitude with new borders
(40.614, -84.052) (54.263, -76.513) (44.268,-52.644) (32.869,-63.768).
#####Reading, extracting and sub setting the grid
library(ncdf)
AIR1=open.ncdf("air.mon.mean.nc",write=FALSE,readunlim=TRUE)
print(AIR1)
AIR2=AIR1$var[[2]]
AIR=get.var.ncdf(AIR1,AIR2,start=c(1,1,13,1),count=c(349,277,1,372))
AIR_JAN_1979=AIR[234:297,120:170,1]
AIR2LAT=AIR1$var[[3]]
AIR_LAT_19791=get.var.ncdf(AIR1,AIR2LAT,start=c(1,1),count=c(349,277))
AIR_LAT_1979=AIR_LAT_19791[234:297,120:170]
AIR2LONG=AIR1$var[[4]]
AIR_LONG_19791=get.var.ncdf(AIR1,AIR2LONG,start=c(1,1),count=c(349,277))
AIR_LONG_1979=AIR_LONG_19791[234:297,120:170]
#######file information on projection and orientation of grid
int Lambert_Conformal[] "
grid_mapping_name: lambert_conformal_conic"
standard_parallel: 50" " standard_parallel: 50"
longitude_of_central_meridian: -107"
latitude_of_projection_origin: 50"
false_easting: 5632642.22547"
false_northing: 4612545.65137"
y Size:277" #### Original size of grid, extracted one is only 64 x 51
long_name: northward distance from southwest corner of domain in
projection coordinates"
units: m"
standard_name: projection_y_coordinate"
x Size:349"
long_name: eastward distance from southwest corner of domain in
projection coordinates"
units: m"
standard_name: projection_x_coordinate"
nbnds Size:2"
simple plots such as filled.contour will plot the results, but are not
projected properly.
I imagine there is a method within rgdal{spTransform} to correctly display this
data in its projected format or perhaps transform these positions, but it
eludes me at this time. Somewhat similar questions have appeared online, but
the answers I have found do not give correct projections. Any help with this
would be appreciated. Thanks in advance for what may be a simple
transformation,
Walt
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