Support for landscape index calculations on raster

DESCRIPTION

This documentation is focused on scientists and developers who wants to implement a new landscape index computation. Refer to the r.li modules overview and g.gui.rlisetup module for user-focused documentation.

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:

1

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)

where:

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

This function has to return 1 on success and 0 otherwise. This function type is defined using typedef named rli_func.

2

Create a main for command line arguments parsing, and call the function



        int calculateIndex(char *file, rli_func *f,


                           char **parameters, char *raster, char *output);

from the r.li library, for starting raster analysis.
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.

NOTES

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.

REFERENCES

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)

AUTHORS

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

SOURCE CODE

Available at: Support for landscape index calculations on raster source code (history)

Accessed: Saturday Jul 19 12:10:32 2025