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NAME

r.mblend - Blends two rasters of different spatial resolution.

KEYWORDS

raster, resolution

SYNOPSIS

r.mblend
r.mblend --help
r.mblend [-a] [high=string] [low=string] [output=string] [far_edge=value] [inter_points=value] [--help] [--verbose] [--quiet] [--ui]

Flags:

-a
Assign the average difference between the two rasters to the far edge (instead of zero).
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters:

high=string
low=string
output=string
far_edge=value
Percentage of distance to high resolution raster used to determine far edge. Number between 0 and 100.
Default: 95
inter_points=value
Number of points to use in interpolation. A higher number produces a smoother result but requires a lengthier computation.
Default: 50

Table of contents

DESCRIPTION

This module implements Mblend, a DEM merging method proposed by Leitão et al. (2016). It deals with cases where a study area is only partially covered by a high resolution DEM, with a coarser DEM available for the remainder (as in the case shown below). r.mblend merges the two DEMs, producing a smooth transition from the high resolution DEM to the low resolution DEM.



The module works by identifying the edge between the two rasters (near edge, shown in read below) and the edge composed by the cells in the low resolution DEM farther away from the high resolution raster (far edge, shown in blue below). To each point along the near edge is assigned the difference between the two DEMs. To each point in the far edge is assigned the value 0. The Inverse Distance Weighted (IDW) method is then used to interpolate a new raster with the points along the two edges. This differences raster thus trends from the full difference at the near edge towards zero at the far edge.



The differences raster is finally added to the low resolution DEM given as input. In the resulting DEM, cells along the near edge take the values in the high resolution raster. The farther away from the near edge (and closer to to the far edge) the closer is their value is to the low resolution raster, producing a smooth transition, without artefacts.

EXAMPLES

Merge the best_dem and other_dem raster maps from the current mapset:
r.mblend high=best_dem low=other_dem output=result
Modifying the far edge distance cut-off:
r.mblend high=best_dem low=other_dem output=result far_edge=90

REFERENCES

J.P. Leitão, D. Prodanovic, C. Maksimovic, Improving merge methods for grid-based digital elevation models, Computers & Geosciences, Volume 88, March 2016, Pages 115-131, ISSN 0098-3004, http://doi.org/10.1016/j.cageo.2016.01.001.

SEE ALSO

The source code implementing this module is also available at GitHub.

AUTHORS

Luís Moreira de Sousa
EAWAG: Swiss Federal Institute of Aquatic Science and Technology.

Last changed: $Date: 2017-05-24 15:46:44 +0200 (Wed, 24 May 2017) $

SOURCE CODE

Available at: r.mblend source code (history)


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