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I have been working with NetCDF files from Daymet and my project involves extracting data from various files, modifying them and creating new files in R which will then be analyzed in Arcmaps. Using the make NetCDF raster layer tool with with x and y as the dimensions works fine with unmodified data from day met but does nothing to the files I made myself. Using coordinate variables works for both of them but the product comes out distorted. Looking at the differences between the files I created the only difference is that the ones I created don't have any spatial reference coordinates.

There is an existing spatial reference or projection in the unmodified file, which looks like in the metadata:

' 5 variables (excluding dimension variables):
float time_bnds[nv,time]
time: days since 1980-01-01 00:00:00 UTC

' short lambert_conformal_conic[]
grid_mapping_name: lambert_conformal_conic
longitude_of_central_meridian: -100
latitude_of_projection_origin: 42.5
false_easting: 0
false_northing: 0
standard_parallel: 25
standard_parallel: 60
semi_major_axis: 6378137
inverse_flattening: 298.257232666016

With the netcdf r package was able to create something similar looking this code:

' corddef <- ncvar_def("lambert_conformal_conic","", list(), prec="short") ncatt_put(ncout, "lambert_conformal_conic", "grid_mapping_name", "lambert_conformal_conic") ncatt_put(ncout,"lambert_conformal_conic","longitude_of_central_meridian", "-100") ncatt_put(ncout,"lambert_conformal_conic","latitude_of_projection_origin", "42.5") ncatt_put(ncout,"lambert_conformal_conic","false_easting", "0") ncatt_put(ncout,"lambert_conformal_conic","false_northing", "0") ncatt_put(ncout,"lambert_conformal_conic","standard_parallel", "25") ncatt_put(ncout,"lambert_conformal_conic","standard_parallel_2", "60") ncatt_put(ncout,"lambert_conformal_conic","semi_major_axis", "6378137") ncatt_put(ncout,"lambert_conformal_conic","inverse_flattening", "298.257232666016")

Which gives this:

' 5 variables (excluding dimension variables):
float time_bnds[time] (Chunking: [1])
units: days since 1980-01-01 00:00:00 UTC
short lambert_conformal_conic[] (Contiguous storage)
grid_mapping_name: lambert_conformal_conic
longitude_of_central_meridian: -100
latitude_of_projection_origin: 42.5
false_easting: 0
false_northing: 0
standard_parallel: 25
standard_parallel_2: 60
semi_major_axis: 6378137
inverse_flattening: 298.257232666016

Trying to make a raster out of it in Arcmaps still doesn't do anything though so I was wondering if there was a better way to put the information about the projection directly into the new file I'm creating so that arcmaps can automatically read the information.

Cooper Springer
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1 Answers1

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The code has to be done like this, with the numbers you want to add assigned a name. 

longitude_of_central_meridian <- -100
latitude_of_projection_origin <- 42.5
false_easting <- 0
false_northing <- 0
semi_major_axis <- 6378137
inverse_flattening <- 298.257232666016

ncatt_put(ncout, "lambert_conformal_conic", "grid_mapping_name", "lambert_conformal_conic")
ncatt_put(ncout,"lambert_conformal_conic","longitude_of_central_meridian", longitude_of_central_meridian)
ncatt_put(ncout,"lambert_conformal_conic","latitude_of_projection_origin", latitude_of_projection_origin)
ncatt_put(ncout,"lambert_conformal_conic","false_easting", false_easting)
ncatt_put(ncout,"lambert_conformal_conic","false_northing", false_northing)
ncatt_put(ncout,"lambert_conformal_conic", "standard_parallel", c(25,60))
ncatt_put(ncout,"lambert_conformal_conic","semi_major_axis", semi_major_axis)
ncatt_put(ncout,"lambert_conformal_conic","inverse_flattening", inverse_flattening)
Cooper Springer
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