Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.

**-c**- Use circular window (default: square)
**-s**- Add slope convergence (radically slows down calculation time)
**--overwrite**- Allow output files to overwrite existing files
**--help**- Print usage summary
**--verbose**- Verbose module output
**--quiet**- Quiet module output
**--ui**- Force launching GUI dialog

**input**=*name***[required]**- Digital elevation model map
**output**=*name***[required]**- Output convergence index map
**window**=*integer***[required]**- Window size
- Default:
*3* **weights**=*string***[required]**- Method for reducing the impact of the cell due to distance
- Options:
*standard, inverse, power, square, gentle* - Default:
*standard*

**-s**- Increase convergence if slope value is high. Slope parameter radically slows down computation time, especially if the window parameter is high. If slope is used, a slope modifier is used according to the formula: sin(current)*sin(target) + cos(current)*cos(target). If the slope of current and target cells are equal, this modifier's value will be 1. The modifier is applied with the formula: acos(cos(convergence) * modifier)
**-c**- Use circular window instead of square (default)
**input**- Digital elevation model. Data can be of any type and any projection.
To calculate relief convergence,
*r.convergence*uses real distances which is recalculated into cell distance, according formula:

`distance_between_current_cell_and_target_cell/distance_between_current_cell_and_nearest_neighbour_cell.`

It is important if convergence is calculated for large areas in Lat/Lon projection. **weights**- Parameter describing the reduction of the impact of the cell
due to its distance, where distance in cells:
**standard:**no decay**inverse:**distance modifier is calculated as 1/x**power:**distance modifier is calculated as 1/(x*x)**power:**distance modifier is calculated as 1/(x*x)**gentle:**distance modifier is calculated as 1/((1-x)/(1+x))

**window**- Window size. Must be odd. For now there are no limits in window size.
*r.convergence*uses the window size instead of classical radius for compatibility with other GRASS GIS commands. **output**- Map of convergence index. The values ranges from -100 (max divergent, real peaks and ridges) by 0 (planar areas) to 100 (max convergent, real pits and channels). Classical convergence index presented with degrees (-90 to 90)

Claps, P., Fiorentino, M., Oliveto, G., (1994), *Informational entropy of fractal river networks*,
Journal of Hydrology, 187(1-2), 145-156 .

Bauer J., Rohdenburg H., Bork H.-R., (1985), Ein Digitales Reliefmodell als Vorraussetzung fuer ein deterministisches Modell der Wasser- und Stoff-Fluesse, *IN: Bork, H.-R., Rohdenburg, H., Landschaftsgenese und Landschaftsoekologie, Parameteraufbereitung fuer deterministische Gebiets-Wassermodelle, Grundlagenarbeiten zu Analyse von Agrar-Oekosystemen*, 1-15.

Böhner J., Blaschke T., Montanarella, L. (eds.) (2008). SAGA Seconds Out. Hamburger Beiträge zur Physischen Geographie und Landschaftsökologie, 19: 113 s.

Available at: r.convergence source code (history)

Latest change: Monday Jan 03 13:11:04 2022 in commit: cdaf77af4e1797eb54761002692a28d2275cf0b5

Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.

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