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The lakewalker plugin is a kind of simple vectorisation software. It performs simple image recognition on Landsat imagery to automatically trace around the edge of lakes, island or coastline, to create vector data (nodes and ways directly within JOSM) It utilizes the algorithm of lakewalker python scripts originally written by Dshpak.

Lakewalker is no longer actively developed and is considered 'dead' Use Scanaerial instead.


Preferences panel in the JOSM preferences area contains:

  • Maximum Segments per way - default 250
  • Maximum nodes in initial trace - default 50,000
  • Maximum grey value to count as water - default 35 (old standard - to be used with the python script) / 90 (new standard)
  • Line Simplification accuracy - default 0.0003; the smaller the value the more nodes in the final trace
  • Resolution of Landsat tiles (pixels per degree) - default 4000; the smaller the value the less detailed the trace
  • Size of landsat tiles (pixels) - default 2000 (maybe better to be set to 250)
  • Shift all traces (east/north) - default 0.0; useful if you know the landsat imagery is off
  • Direction to search for land - default east; The tracer will move this direction from the starting coordinate looking for the edge of the water
  • Tag ways as - default water; All ways will be tagged as natural=(water|coastline|land) or not tagged if none selected


Install the plugin from the JOSM preferences panel or download the lakewalker.jar.

Known Issues

  • Some traces will get caught in a loop, if it hits the maximum initial node value (default is 50,000) try moving the view or zooming a bit and try again.

Error Checking

For big lakes and islands one should use the Coastline error checker later on (after the next checker run) to check whether all went well (see: Coastline error checker for details).