Hi,
Here is a question about data-type conversion done by the netcdf-c library.
I have a file with short data, but I am trying to read the data as float using nc_get_vara_float.
This will make it easier for me to apply scale and offset factors later on.
I noticed that the short value of -1 is changed to 65535 when reading it with the nc_get_vara_float
function, while for attributes the value stays -1, when using the nc_get_att_float function.
Is this expected behaviour? Below a small test program which illustrates this:
#include <stdio.h>
#include <netcdf.h>
int main(){
int status;
int ncid;
int varid;
static size_t start[] = {0, 0, 0};
static size_t count[] = {1, 1, 1};
float varData[1];
float attrData[1];
status =
nc_open("http://opendap.nmdc.eu/knmi/thredds/dodsC/radarprecipclim/RAD_NL21_RAC_MFBS_01H_NC.nc";, 0,
&ncid);
if (status != NC_NOERR) {return 1;}
status = nc_inq_varid (ncid, "image1_image_data", &varid);
if (status != NC_NOERR) {return 2;}
status = nc_get_vara_float(ncid, varid, start, count, varData);
if (status != NC_NOERR) {return 3;}
status = nc_get_att_float(ncid,varid,"_FillValue",attrData);
if (status != NC_NOERR) {return 4;}
nc_close(ncid);
printf("Vardata : %f\t\nAttrdata: %f\n",varData[0],attrData[0]);
return 0;
}
it returns:
Vardata : 65535.000000
Attrdata: -1.000000
I would expect that both values are -1?
Best regards,
Maarten Plieger
--
Maarten Plieger
KNMI, R&D Information and Observation Technology, De Bilt
(t) +31 30 2206330
