Changes between Version 25 and Version 26 of PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools/document

Timestamp:

Jul 12, 2012, 11:16:35 PM (12 years ago)

Author:

qliu

Comment:

—

PostGIS_Raster_SoC_Idea_2012/Distance_Analysis_Tools/document

@@ -90 +90 @@
  * __This approach fulfills constraint 7 in that it would allow easy implementation of other interpolation methods.__
 {{{
-Comments from the mentor:
+Comments from Mentor:
 Not really. If the raster HAS to be in the extent of the point coverage, as stated in the cons, it means it could not correspond to the arbitrary alignment/extent of an existing coverage. This is probably the main reason the third approach is preferable to the TIN one.
 }}}
@@ -97 +97 @@
  * __We have no idea for now about the algorithm and performance of building TIN from source geometries in PostGIS if the number of source point is very large (Constraint 7 & 8)__
 {{{
-Comments from the Mentor:
+Comments from Mentor:
 Right, ST_Within(raster, geometry) does not exist. But you would work with the centroid of the pixel, which is a point and the triangle of the TIN which are polygons and there is no problem doing that with ST_Within. If you would include the pixel centroid in the TIN as stated above, you would nort even have to do that as the centroid and the points would all be in the same TIN structure allowing fast find of neighbors.
 }}}
@@ -133 +133 @@
 
 '''Cons:'''
- * Might not be as light as Approach 1 in case there is only one point in the source table (Constraint 1) or there are very small number of source points and the requested raster is relatively small too (Constraint 5)
- * Have no idea how to deal with Constraint 9.
+ * __Might not be as light as Approach 1 in case there is only one point in the source table (Constraint 1) or there are very small number of source points and the requested raster is relatively small too (Constraint 5)__
+{{{
+Comments from Mentor:
+In that case, should be fast anyway. We could optimize if there is only one source point.
+}}}
 
 [[BR]][[BR]]
@@ -172 +175 @@
  * For Constraint 6: (just write down the function that takes a reference raster for example)
 {{{
-#!c
+#!c++
 ST_EuclideanDistance(text dbschema, text sourcetable, text sourcegeomcolumn, raster ref, text pixeltype, double precision value=1, double precision nodataval=0, double precision maxdistance)
 }}}
+{{{
+Comments from Mentor:
+You should integrate this parameter in the more generic signature instead. The idea is to create a generic function with the most complete signature and then to create variants assuming default value for some of the parameters. Only the most complete has to be implemented in C.
+}}}