Changes between Version 78 and Version 79 of WKTRasterTutorial01

Timestamp:

Jun 29, 2010, 1:59:04 PM (14 years ago)

Author:

pracine

Comment:

—

WKTRasterTutorial01

@@ -173 +173 @@
 Vectorizing all the table would have been way too long and the huge amount of geometry would have been impossible to load in OpenJUMP (and most GIS software).
 
-First notice: some pixels are grouped together into complex polygons. ST_DumpAsPolygons() not only blindly dump each pixels, it actually vectorize the raster grouping areas with shared values together. In a raster with an low range of value this would result in significantly less polygones than there is pixels. Higher number of different value (like continuous floating point value rasters) would result in many, many little polygons, most of them square corresponding to only one pixel. A future ST_Reclass() unction should help reducing the number of value in a raster and give more analysis flexibility. For now you can always reclassify your raster BEFORE loading them into PostGIS WKT Raster.
+First notice: some pixels are grouped together into complex polygons. ST_DumpAsPolygons() not only blindly dump each pixels, it actually vectorize the raster grouping areas with shared values together. In a raster having a low range of values, this would result in a significantly lower number of polygons than the number of pixels. A higher number of different values (like continuous floating point value rasters) would result in many, many little polygons, most of them square corresponding to only one pixel. A future ST_Reclass() unction should help reducing the number of value in a raster and give more analysis flexibility. For now you can always reclassify your raster BEFORE loading them into PostGIS WKT Raster.
 
 This query includes the value associated each group of pixel. You can display those values by right-clicking on the OpenJUMP layer, selecting "Change Styles...", selecting the "Labels" tab, "Enabling labelling" and selecting the "val" Label attribute.