WxGUI Map Swipe

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Revision as of 13:31, 16 August 2012 by Hellik (talk | contribs) (Introduction)

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The Map Swipe is a wxGUI application which allows GRASS users to interactively compare two raster maps of the same area by revealing different parts of the raster maps. It is useful e.g. for comparing raster maps from different time periods. See also the manual.

The Map Swipe is available in GRASS 7 from the menu

File -> Map Swipe

and will be backported to GRASS 6 after some testing.

wxGUI Map Swipe

Implemented features:

  • orientation of the swipe line can be changed (horizontal or vertical)
  • zooming, panning
  • maps are loaded automatically when opening Map Swipe with two selected raster maps in Layer Manager

Possible enhancements:

  • add simplified layer manager for each window so that you can add any maps (raster/vector) - would it be useful?
  • add your idea here

Simple testing:

You can use the North Carolina sample dataset (download) for this test:

# set computation region
g.region rast=lsat7_2002_10 -p

# create RGB composites, first color-balance:
i.landsat.rgb b=lsat5_1987_10@landsat g=lsat5_1987_20@landsat r=lsat5_1987_30@landsat
r.composite b=lsat5_1987_10@landsat g=lsat5_1987_20@landsat r=lsat5_1987_30@landsat out=lsat7_1987.rgb

i.landsat.rgb b=lsat7_2002_10 g=lsat7_2002_20 r=lsat7_2002_30
r.composite b=lsat7_2002_10 g=lsat7_2002_20 r=lsat7_2002_30 out=lsat7_2002.rgb

# .. now load the two RGB composites into the "Map Swipe" tool.
Comparison of Landsat5/1987 and Landsat7/2002 near Raleigh, NC, USA

Disaster analysis

The Map swipe tool is particularly interesting for pre and post disaster analysis of satellite or other images.

Screenshot of map comparison:

Pre and post disaster images of the tsunami in Japan in 2011. The upper MODIS image taken on February 26, 2011, shows the coastline under normal conditions while the lower MODIS image on March 13, 2011, shows a clear view of tsunami flooding along the coastline. Water, black and dark blue in these false-color images, still covers the ground as much as five kilometers (three miles) from the coast. Source: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=49634

Video tutorial