GDDs are calculated as
gdd = average - baseline
The Winkler index is calculated as
wi = average - baseline
BEDDs are calculated as
bedd = average - baseline
The Huglin heliothermal index is calculated as
hi = (average + max) / 2 - baseline
Any averages above the cutoff value are set to cutoff, and any average values below the baseline value are set to baseline. Negative results are set to 0 (zero).
The shift and scale values are applied directly to the input values. The baseline, cutoff, and range options are applied to the shifted and scaled values.
If an existing map is provided with the add option, the values of this map are added to the output, thus accumulating the selected index.
new = old * scale + shift
With the -n flag, any cell for which any of the corresponding input cells are NULL is automatically set to NULL (NULL propagation) and the index is not calculated.
Without the -n flag, all non-NULL cells are used to calculate the selected index.
If the range= option is given, any values which fall outside that range will be treated as if they were NULL. Note that the range is applied to the scaled and shifted input data. The range parameter can be set to low,high thresholds: values outside of this range are treated as NULL (i.e., they will be ignored by most aggregates, or will cause the result to be NULL if -n is given). The low,high thresholds are floating point, so use -inf or inf for a single threshold (e.g., range=0,inf to ignore negative values, or range=-inf,-200.4 to ignore values above -200.4).
The number of raster maps to be processed is given by the limit of the operating system. For example, both the hard and soft limits are typically 1024. The soft limit can be changed with e.g. ulimit -n 1500 (UNIX-based operating systems) but not higher than the hard limit. If it is too low, you can as superuser add an entry in
/etc/security/limits.conf # <domain> <type> <item> <value> your_username hard nofile 1500
Use the file option to analyze large amount of raster maps without hitting open files limit and the size limit of command line arguments. The computation is slower than the input option method. For every sinlge row in the output map(s) all input maps are opened and closed. The amount of RAM will rise linear with the number of specified input maps. The input and file options are mutually exclusive. Input is a text file with a new line separated list of raster map names.
r.gdd in=MOD11A1.Day,MOD11A1.Night,MYD11A1.Day,MYD11A1.Night out=MCD11A1.GDD \ scale=0.02 shift=-273.15 baseline=10 cutoff=30
© 2003-2021 GRASS Development Team, GRASS GIS 7.8.6dev Reference Manual