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  Using Soil Erosion Modeling for Improved Conservation Planning: 
A GIS-based Tutorial

Analyzing and communicating the modeling results

Creating maps representing inputs/outputs as continuous phenomena

 

Elevation and its derived parameters, water flow, net erosion and deposition are in general continuous phenomena -  meaning the values change from point to point. Mathematically they are represented as multivariate functions (in our case, bi-variate) z=f(x,y) or q=g(x,y). In GIS such phenomena are discretized, typically using a grid (raster) representation where each grid cell represents a point in the landscape. Graphically, such phenomena can be represented by isolines and/or a color gradient.
Example elevation map
Elevation represented with isolines (and color gradient). Elevation represented with a color gradient.

 

Phenomena with linear isoline interval and color table (elevation, slope)


Phenomena with non-linear isoline interval and color table (water flow, detachment rate, sediment flow, net erosion/deposition)
  • selecting the intervals:
    • depending on the importance of certain values or established conventions (GRASS, ArcGIS example)
    • depending on histogram (GRASS, ArcGIS example)
  • assigning color: sample colortables

 
 

Adding additional relevant information (streams, roads and other man-made features..., shaded topography)

 


 Up
map2d-continuous
map2d-discrete
map3d
 

HOME                                                        H. Mitasova, et al.,  Geographic Modeling Systems Lab, UIUC