[GRASS-user] r.watershed

[Helmut Kudrnovsky]

Shane Carey wrote
> Hi,
> 
> I am trying to extract river network from a 5m DEM with some success using
> r.watershed. Has anyone tested this algorithm on high resolution LiDAR
> data
> for example - 1meter DTM and what kind of results have they obtained?

in the NC sample dateset there is lidar derived 1m x 1m DEM:

r.info map=elev_lid792_1m at PERMANENT                                             

+----------------------------------------------------------------------------+
 | Map:      elev_lid792_1m at PERMANENT       Date: Wed Feb 14 19:45:24 2007   
|
 | Mapset:   PERMANENT                      Login of Creator: helena         
|
 | Location: nc_spm_08_grass7                                                
|
 | DataBase: D:\grassdata                                                    
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 | Title:    Rural area: Lidar-based 1m DEM                                  
|
 | Timestamp: none                                                           
|

|----------------------------------------------------------------------------|
 |                                                                           
|
 |   Type of Map:  raster               Number of Categories: 255            
|
 |   Data Type:    FCELL                                                     
|
 |   Rows:         750                                                       
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 |   Columns:      700                                                       
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 |   Total Cells:  525000                                                    
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 |        Projection: Lambert Conformal Conic                                
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 |            N:     220750    S:     220000   Res:     1                    
|
 |            E:     639000    W:     638300   Res:     1                    
|
 |   Range of data:    min = 103.7643  max = 131.598                         
|
 |                                                                           
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 |   Data Source:                                                            
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 |    vector file ncfl_lidar_79200WC_pts                                     
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 |                                                                           
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 |                                                                           
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 |   Data Description:                                                       
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 |    generated by v.surf.rst                                                
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 |                                                                           
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 |   Comments:                                                               
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 |    giventension=300.000000, smoothing=1.000000                            
|
 |    dnorm=47.606041, dmin=1.000000, zmult=1.000000                         
|
 |    segmax=25, npmin=100, rmsdevi=0.222627                                 
|
 |    zmin_data=103.513000, zmax_data=131.668000                             
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 |    zmin_int=103.764260, zmax_int=131.598045                               
|
 |                                                                           
|
 |    v.surf.rst -t input="ncfl_lidar_79200WC_pts" layer=0 elev="elev_lid7\  
|
 |    9200_1m" slope="slope_1m" aspect="asp_1m" pcurv="pcurv_1m" tcurv="tc\  
|
 |    urv_1m" tension=300 smooth=1.0 segmax=25 npmin=100 dmin=1 dmax=2.500\  
|
 |    000 zmult=1.0                                                          
|
 |                                                                           
|

+----------------------------------------------------------------------------+

you can test the module with this DEM to see it's appropriate for your need.






-----
best regards
Helmut
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