Support for landscape index calculations on raster
This documentation is focused on scientists and developers who wants to
implement a new landscape index computation. Refer to the
modules overview and
module for user-focused
r.li.daemon provides support for landscape index calculations on raster
maps. It hides the management of areas, defined using g.gui.rlisetup
command. It is not used like a standalone program, but its functions are
a library used by all r.li.[index] commands.
This description is a tutorial for new index definition.
The developer has only to focus on a unique area, like in mathematical definitions, and
has to write a C implementation of it.
The areas are defined using a struct called area_des and it members are
explained in the source code (doxygen) documentation.
To write a new index only two steps are needed:
Define a function and insert its declaration on file index.h in r.li.daemon
folder, which contains all index declarations. This function must be of this kind:
int index(int fd, char ** par, area_des ad, double * result)
This function has to return 1 on success and 0 otherwise.
This function type is defined using typedef named
- fd is the raster map descriptor
- par is a matrix for special parameter (like argv in main)
- ad is the area descriptor
- result is where to put the index calculation result
Create a main for command line arguments parsing, and call the function
from the r.li library, for starting raster analysis.
int calculateIndex(char *file, rli_func *f,
char **parameters, char *raster, char *output);
It follows the meaning of parameters:
- file name of configuration file created using g.gui.rlisetup
- f pointer to index function defined above
- parameters pointer to index special parameters
- raster name of raster to use
- output output file name
Compile it using a changed Makefile based on the file for r.li.patchdensity
Refer to the r.li library documentation in the source code and
implementation of r.li modules for details and examples.
Using GRASS library function to access raster rows can slow down moving windows
execution. It is recommended to use
RLI_get_cell_row(int, int, area_des)
RLI_get_fcell_row(int, int, area_des)
RLI_get_dcell_row(int, int, area_des)
to use an ad hoc build memory management developed to speed up the system.
The documentation is in doxygen files.
old r.le manual
- package overview
McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern
analysis program for quantifying landscape structure. USDA For. Serv.
Gen. Tech. Rep. PNW-351. (PDF
Claudio Porta and Lucio Davide Spano, students of Computer Science
University of Pisa (Italy).
Commission from Faunalia Pontedera (PI)
Rewritten from "r.le.setup" by William L. Baker
Various bug fixes by Markus Metz
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GRASS GIS 8.2.1dev Reference Manual