Hi all, I would like to briefly weigh in in this discussion, especially about the following:
> 2) Of greater importance is that you can pick either one; it doesn't matter > in the real world. In 1994 I was the first environmental consultant > authorized by Oregon's Department of State Lands to use GPS receivers to > delineate wetland boundaries. They had insisted that only professional land > surveyors could do this and they set a 2cm accuracy standard. Really? > Wetland boundaries are transistion zones that can be several meters wide, > depending on topography, soils, and antecedent precipitation conditions when > the boundary is flagged. A stream bank is an exception to this broad > transition area. When I made the case that there is no sharp line of > demarkation between wetland and upland they accepted my delineations. I couldn't agree more on this point - at times people really have fancy interpretations of maps' resolution and what they can actually tell about the real world. I also would like to add that watershed delineated from a digital topography may depend on the scale at which one looks at the landscape. I mean, not the DEM resolution by the very definition of a watershed - if we agree that this definition depends on the number of cells draining on the outlet (parameter "threshold" on r.watershed), we get very different results depending on this parameter. And now for a little advertising: we discuss these topics and their use to produce slope unit tools (in GRASS GIS) and maps in these papers: "Automatic delineation of geomorphological slope units with r.slopeunits v1.0 and their optimization for landslide susceptibility modeling " https://doi.org/10.5194/gmd-9-3975-2016 "Parameter-free delineation of slope units and terrain subdivision of Italy" https://doi.org/10.1016/j.geomorph.2020.107124 M _______________________________________________ grass-user mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-user
