Changes between Version 27 and Version 28 of Grass7/TemporalGISAlgebra

Timestamp:

Oct 20, 2014, 1:08:31 PM (10 years ago)

Author:

mastho

Comment:

--

Grass7/TemporalGISAlgebra

@@ -98 +98 @@
   if(conditions, A)                    A if conditions are True;              Topological relation between conditions(if) and conclusion(then) is equal.
   if(conditions, A, B)                 A if conditions are True, B otherwise; Topological relation between conditions(if) and conclusions(then + else) is equal.
-  if(topologies, conditions, A)        A if conditions are True;              Topological relation between conditions(if) and conclusions(then) is explicit specified by topologies.
-  if(topologies, conditions, A, B)     A if conditions are True, B otherwise; Topological relation between conditions(if) and conclusions(then + else) is explicit specified by topologies.
+  if({topologies}, conditions, A)      A if conditions are True;              Topological relation between conditions(if) and conclusions(then) is explicit specified by topologies.
+  if({topologies}, conditions, A, B)   A if conditions are True, B otherwise; Topological relation between conditions(if) and conclusions(then + else) is explicit specified by topologies.
 }}}
 The conditions are comparison expressions that are used to evaluate 
@@ -215 +215 @@
 resulting spatial union maps are stored in C with new time stamps resulting from temporal disjoint union:
 {{{
-C = if(start_year(A) > 1990, A {|,equal|overlap,+} B)
+C = if({equal|overlap},start_year(A) > 1990, A {|,equal|overlap,+} B)
 }}}
 
 The temporal vector algebra provides point, line and area buffer functions in addition to the operators.
-
-All supported operators and functions are documented below.
 
 == Temporal Raster Algebra ==
@@ -309 +307 @@
 This statement multiply all raster maps from space time raster data set A with the raster map 'constant_value'
 
+==== Implicit aggregation for spatio-temporal operators ====
+The algebra evaluates the stated STDS by their temporal topologies and apply the given spatio temporal operators in a aggregated form. 
+
+If we have two STDS A and B, B has three maps: b1, b2, b3 that are all during the temporal extent of the single map a1 of A, then the following arithemtic 
+calculations would implicitly aggregate all maps of B into one result map for a1 of A:
+{{{
+C = A {+, contains} B --> c1 = a1 + b1 + b2 + b3
+}}} 
+
+Keep attention that the aggregation behaviour is not symmetric:
+{{{
+C = B {+, during} A --> 
+  c1 = b1 + a1
+  c2 = b2 + a1
+  c3 = b3 + a1
+}}}
+
 = Overview of all supported spatio-temporal operators and functions =