Changes between Version 38 and Version 39 of PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools


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Timestamp:
06/18/12 21:50:22 (13 years ago)
Author:
qliu
Comment:

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  • PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools

    v38 v39  
    113113        * If the cell is at an equal distance to two or more sources, the cell is assigned to the source that is first encountered in the scanning process. User cannot control this scanning process.
    114114        * The actual algorithm computes the information using a two-scan sequential process(need to figure it out?). This process makes the speed of the tool independent from the number of source cells, the distribution of the source cells, and the maximum distance specified. The only factor that influences the speed with which the tool executes is the size of the raster. The computation time is linearly proportional to the number of cells in the Analysis window.
    115       * Reference:
     115      * Reference: [[BR]]
    116116        [http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z0000001p000000.htm]
     117[[BR]][[BR]]
     118    * GRASS
     119      * r.grow.distance or GDAL tools\ Proximity (Raster Distance) in QGIS
     120      * Concepts:
     121        * '''r.grow.distance''' metric=euclidean (default):[[BR]]
     122        generates raster maps representing the distance to the nearest non-null cell in the input map and/or the value of the nearest non-null cell.
     123        * '''gdal_proximity''' generates a raster proximity map indicating the distance from the center of each pixel to the center of the nearest target pixel in the source raster.
     124      * Function:[[BR]]
     125        '''r.grow.distance''' ['''-m'''] '''input'''=name ['''distance'''=name] ['''value'''=name] ['''metric'''=string] [--'''overwrite'''] [--'''verbose'''] [--'''quiet''']
     126        * input: Raster dataset
     127          * Source cell locations are represented with non-null cell value
     128        * distance: Output Raster dataset
     129          * Identifies distances for each cell to the nearest source cell(s)
     130        * metric:
     131          * User specified four different metrics which control the geometry in which grown cells are created
     132          * '''Euclidean''' (by default), Squared, Manhattan, and Maximum[[BR]]
     133        '''gdal_proximity.py''' srcfile dstfile [-srcband n] [-dstband n] [-of format][-co name=value]* [-ot Byte/Int16/Int32/Float32/etc][-values n,n,n] [-distunits PIXEL/GEO] [-maxdist n] [-nodata n][-fixed-buf-val n]
     134        * srcfile: Raster file, identifies target pixels
     135        * dstfile: Output Raster file of proximity (distance)
     136        * -values: [[BR]]
     137          A list of target pixel values in the source image to be considered target pixels. If not specified, all non-zero pixels will be considered target pixels.
     138        * -mxdist:[[BR]]
     139          The maximum distance to be generated. All pixels beyond this distance will be assigned the nodata value.
     140      * Algorithm:
     141        * d(dx,dy) = sqrt(dx^2 + dy^2)
     142        * Cells grown would form isolines of distance that are circular from a given point, with the distance given by the radius.
     143      * Reference: [[BR]]
     144        [http://grass.osgeo.org/manuals/html70_user/r.grow.distance.html][[BR]]
     145        [http://www.gdal.org/gdal_proximity.html]
    117146
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