Changes between Version 233 and Version 234 of WKTRaster/SpecificationWorking03

Timestamp:

08/27/12 10:57:47 (12 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking03

@@ -118 +118 @@
   2) Functions searching for the pixel value in a vector coverage. This is the same principle as ST_UnionToRaster() and ST_BurnToRaster().
 
-  3) Functions aggregating pixel values from a raster neighborhood. This is the same principle as ST_MapAlgebraFctNbg() except that the rasters do not have to be aligned (nice advantage!).
-
-  4) Functions aggregating pixel values from a neighborhood. This is the only way to do that.
+  3) Functions aggregating pixel values from a raster neighborhood. This is the same principle as ST_MapAlgebraFctNbg() except that the target raster do not have to be aligned with the source raster (nice advantage!).
+
+  4) Functions aggregating pixel values from a vector neighborhood. This is the only way to do that.
 
   5) Functions deriving metric values from a raster or a geometry coverage. This is very similar to the two previous items but the result is not an aggregate value. e.g. Distance to something.
@@ -128 +128 @@
  * Some examples of such custom functions exists:
 
-  * ST_FasterUnion('schemaname', 'tablename', 'rastercolumnname'), an alternative to ST_Union(rast, 'LAST') - Merge all the tiles of a table together into a single raster. This function is described [http://geospatialelucubrations.blogspot.fr/2012/07/a-slow-yet-1000x-faster-alternative-to.html here]. this function is dependent on the ST_FirstRasterValue4ma() ST_MapAlgebraFct() custom function. 
+  * ST_FasterUnion('schemaname', 'tablename', 'rastercolumnname'), a temporary alternative to ST_Union(rast, 'LAST') - Merge all the tiles of a table together into a single raster. This function act as a wrapper around the ST_FirstRasterValue4ma() ST_MapAlgebraFct() custom function and is described [http://geospatialelucubrations.blogspot.fr/2012/07/a-slow-yet-1000x-faster-alternative-to.html here]. 
 
   * ST_FirstGeomValue4ma() - Get the value from a specified column from the first geometry intersecting with the shape of the pixel (See [http://postgis.refractions.net/pipermail/postgis-users/2012-April/033875.html this post to postgis-users])
@@ -134 +134 @@
  * Other possible functions:
 
-  * ST_GeomToRaster('schemaname', 'tablename', 'geomolumnname', 'METHOD') - A generalization of ST_FirstGeomValue4ma() described above but accepting more methods of value extraction, depending on the type of coverage we want to extract from. This is very much like doing an intersection (actually more like an "identify" overlay operation) between a raster and a vector coverage.
+  * ST_GeomToRaster('schemaname', 'tablename', 'geomolumnname', 'METHOD') (Category 2) - A generalization of ST_FirstGeomValue4ma() described above but accepting more methods of value extraction, depending on the type of coverage we want to extract from. This is very much like doing an intersection (actually more like an "identify" overlay operation) between a raster and a vector coverage.
+
+  This function can further be generalised by adding parameters to define a buffer area around the pixel centroid or the pixel boundary. This would provide a category 4 type of function.
 
  The METHOD could be:
@@ -143 +145 @@
 
   * from a polygon coverage could also be MAX_AREA, MIN_AREA, AREA_RANGE, AREA_SUM, AREA_MEAN, AREA_STDDEV, COMBINED_MAX_AREA, COMBINED_MIN_AREA, COMBINED_MEAN_AREA, COMBINED_STDDEV_AREA, AREA_OF_POLYGON_WITH_GREATEST_VALUE, AREA_OF_POLYGON_WITH_SMALLEST_VALUE, AREA_OF_POLYGON_WITH_MOST_FREQUENT_VALUE, AREA_OF_LEAST_FREQUENT_VALUE, VALUE_OF_LARGEST, VALUE_OF_SMALLEST, VALUE_OF_COMBINED_LARGEST, VALUE_OF_COMBINED_SMALLEST, WEIGHTED_SUM, WEIGHTED_MEAN
+
+  * ST_EuclidianDistance() (see [http://trac.osgeo.org/postgis/wiki/PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools the GSoC project]) 
 
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