Changes between Version 10 and Version 11 of Grass7/TemporalGISAlgebra

Timestamp:

Jul 5, 2013, 8:11:35 AM (11 years ago)

Author:

huhabla

Comment:

--

Grass7/TemporalGISAlgebra

@@ -1 +1 @@
 = Temporal GIS Algebra for Raster and Vector Data =
 
-== Introduction ==
-
-=== Temporal Algebra ===
+== Temporal Algebra ==
 
 The idea is to implement a temporal algebra to process space time datasets, 
@@ -103 +101 @@
 This expression selects all maps from A that temporally contains at least 2 maps from B and stores them in space time dataset C.
 The leading '''equal''' statement in the '''if''' condition specifies the temporal relation between the if and then part of the expression. This is very important, so we do not need to specify a time reference for temporal processing.
+
+==== Temporal Operators ====
+The temporal algebra defines temporal operators that can be combined later with the spatial operators to perform spatio-temporal operations. 
+The temporal operators process the time instances and intervals of temporal related maps. 
+{{{
+AND             &       Intersection 
+OR              |       Union
+DISJOINT OR     +       Disjoint union
+LEFT REFERENCE  =       Use the time stamp of the left space time vector dataset
+}}}
+For example we can compute the intersection, union or disjoint union from time stamps of maps 
+that temporally overlap, or we can just keep the time stamp of the left STDS.
+{{{
+Left Operator  Right
+   A {equal,:} B
+}}}
+
+== Temporal Vector Algebra ==
+
+The temporal vector algebra includes all functions from the temporal algebra 
+and adds spatial boolean and buffer operations that can be performed on temporal related vector maps that are registered in 
+space time vector datasets.
+
+=== Spatio-Temporal Operators ===
+
+These are the spatial operators that are supported:
+{{{
+AND             &       Intersection            (v.overlay operator=and)
+OR              |       Union                   (v.overlay operator=or)
+DISJOINT OR     +       Disjoint union          (v.patch)
+XOR             ^       Symmetric difference    (v.overlay operator=xor)
+NOT             ~       Complement              (v.overlay operator=not)
+}}}
+We combine the temporal topology relations, the temporal operators and the spatial operators to create spatio-temporal operators:
+{{{
+{"list of temporal relations", "temporal operator" "spatial operator"} 
+}}}
+The spatial operator can be used stand-alone. In this case the temporal topology relation "equal" and the temporal operator "left reference =" is assumed and used as default. This allows the convenient use of the spatial operators in case of space time vector datasets with equal time stamps.
+
+Example:
+A spatio intersection between maps of STVDS A and B that are temporally equal, 
+resulting spatial intersection maps are stored in C with time stamps from A:
+{{{
+C = A & B
+}}}
+A spatio-temporal intersection between maps of STVDS A and B that temporally overlap, 
+resulting spatial intersection maps are stored in C with new time stamps resulting from temporal intersection:
+{{{
+C = A {overlap,&&} B
+}}}
+Perform a spatial union and a temporal disjoint union between all maps of STVDS A 
+and B that are temporally equal or overlap and are later than 1990, 
+resulting spatial union maps are stored in C with new time stamps resulting from temporal disjoint union:
+{{{
+C = if(start_year() > 1990, A {equal,overlap,+|} B)
+}}}
+
+
+
+
 = Overview of all temporal algebra elements =