Get data from OpenDap server that requires authentication using R

问题

I'm trying to get data from an OPeNDAP server using R and the ncdf4 package. However, the nasa eosdis server requires username / password. How can I pass this info using R?

Here is what I'm trying to do:

require(ncdf4)
f1 <- nc_open('https://disc2.gesdisc.eosdis.nasa.gov/opendap/TRMM_L3/TRMM_3B42.7/2018/020/3B42.20180120.15.7.HDF')

And the error message:

Error in Rsx_nc4_get_vara_double: NetCDF: Authorization failure syntax error, unexpected WORD_WORD, expecting SCAN_ATTR or SCAN_DATASET or SCAN_ERROR context: HTTP^ Basic: Access denied. Var: nlat Ndims: 1
Start: 0 Count: 400 Error in ncvar_get_inner(d$dimvarid$group_id, d$dimvarid$id, default_missval_ncdf4(), : C function R_nc4_get_vara_double returned error

I tried the url https://username:password@disc2.... but that did not work also.

回答1:

Daniel,

The service you are accessing is using third-party redirection to authenticate users. Therefore the simple way of providing credentials in the URL doesn't work.

You need to create 2 files.

A .dodsrc file (a RC file for the netcdf-c library) with the following content

HTTP.COOKIEFILE=.cookies
HTTP.NETRC=.netrc
A .netrc file, in the location referenced in the .dodsrc, with your credentials:

machine urs.earthdata.nasa.gov
login YOURUSERNAMEHERE
password YOURPASWORDHERE

You can find more details at https://www.unidata.ucar.edu/software/netcdf/docs/md__Users_wfisher_Desktop_v4_86_81-prep_netcdf-c_docs_auth.html

Regards

Antonio

来源：https://stackoverflow.com/questions/52098781/get-data-from-opendap-server-that-requires-authentication-using-r

标签

ncdf4

opendap