PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

The final result is a set of geometry-pixel value pairs representing the shared portion of the geometric
and the vectorization of the raster (Figure 4.54). This result is the same as the one obtained
from the intersection(vector,vector) → vector operation.
Example 2.4: A raster and raster intersection with a raster layer as a result.
Figure 4.55: Mutual exclusive raster-raster intersection with a resulting raster layer [22].
The same, the results are stored in multiband rasters as different disjoint objects as shown in Figure
4.55. To obtain a result similar to the intersection(vector,vector) → vector operation, the resulting
rasters must be vectorized.
4.20 Temporal Raster
By definition, continuous fields are phenomena that are perceived as having a value at each point in
space and time. Temporal raster, an extension of raster, is a new type designed to take into account
the temporal aspect. In addition, a set of operations allowing interactions between this new type with
date and time [2] are also implemented.
PostgreSQL provides different languages to support new types defined by user, such as C, PL/pgSQL.
PL/pgSQL is a procedural language that allows user to create new types, complex functions and etc.
It is easy to learn and can do anything that can be done in C language. The rest of this section
introduces the new temporal raster type and different functions built using PL/pgSQL.
4.20.1 Structure
Temporal raster is defined as a new composite data type based on raster type and timestamp type:
st_rastertemp( rast raster, temp timestamp)
4.20.2 Operations
Operation ST_InTime is a constructor of temporal raster. It yields for each input raster, a
corresponding temporal raster whose value is a pair of a timestamp instant and a raster value. A
simple pseudocode for ST_InTime is shown below:
Example:
SELECT ST_InTime(raster, ’5/12/2011’)
FROM rasterTable;
Inversely, ST_Instant and ST_Value operations retrieve respectively the timestamp instant and
the raster value of the input temporal raster.
Example :
SELECT ST_Instant(tempRast), ST_Value(tempRast)
FROM tempRasterTable;
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