Changes between Version 49 and Version 50 of PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools

Timestamp:

06/22/12 12:03:36 (13 years ago)

Author:

qliu

Comment:

--

PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools

@@ -367 +367 @@
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-<br>
 <b>Comment from Mentor:</b>
 <p>
 I don't think this is a good idea as you would have no control on the alignment of the raster produced. I want to be able to control the dimensions and how the raster is georeferenced. I think your best friend here is ST_AsRaster() which allows passing a geometry and some raster properties and burns the geometry in the raster. Basically ST_AsDistanceRaster() should not be so different from ST_AsRaster(), the only difference is that instead of burning the geometry in the raster, we compute a distance to the geometry for each pixel. It is very possible in this case that the geometry will be outside the extent of the requester raster. Should we want this to work for lines and polygons?
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@@ -385 +383 @@
 #!html
 <div style='background-color: #F4F4F4; border: 1px solid gray; width:800px; padding:10px' >
-<br>
 <b>Comment from Mentor:</b>
 <p>
 You should avoid to do two passes to compute the final pixel values: one to compute the distance in pixel/cell and another to convert into the geographical distance.
 </p>
-<br>
 </div>
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@@ -411 +407 @@
 <b>Comment from Mentor:</b>
 <p>
-- "Algorythm: a. Make an empty raster new_rast, using the same extent as the input vector point data source_point, set pixel value to NoData value." I don't think this is a good idea as you would have no control on the alignment of the raster produced. I want to be able to control the dimensions and how the raster is georeferenced. I think your best friend here is ST_AsRaster() which allows passing a geometry and some raster properties and burns the geometry in the raster. Basically ST_AsDistanceRaster() should not be so different from ST_AsRaster(), the only difference is that instead of burning the geometry in the raster, we compute a distance to the geometry for each pixel. It is very possible in this case that the geometry will be outside the extent of the requester raster. Should we want this to work for lines and polygons?<br>
-<br>
--You should avoid to do two passes to compute the final pixel values: one to compute the distance in pixel/cell and another to convert into the geographical distance.<br>
-<br>
 -What do ArcGIS and GRASS do when there is more than one point? We need a more detailed approach for this case.<br>
 <br>