it reads the gis file defined in the ds
then extract the data at coordinates defined in each sheet of the xls_in file
and then write the data in the xls_out file
the header of the data in the xls_out are written as defined in the
ds_short_name
xls_in: the name of the input xls file containing the co-ordinates of the plot
xls_out: the xls file in which the output will be written
ds: the data source file name in the gis format, these files must be in the
tiff format
ds_short_name: the name that will appear as header in the output xls file