GIS Data in Staging Area Database
|This section is under construction|
When polygon/polyline is linked with the main object the properties from the main object applies to the entire object. This also applies to calculated area and length e.g. if Land-35 has three polygons with (total) calculated area 200 m2 then 200 is repeated on the three polygon rows.
Point, Polyline and Polygon tables
If the option of generating geodata has been chosen on the Staging Area Generator interface, then three related tables with geodata are generated for every object/table that has geographical information:
The tables contain special geographical columns:
- <OBJECT>_POINT: contains all the data related to points defined on the object, with the following main information:
- point_type: e.g. Benchmark, Landmark, Turning Point (all points making up a polygon are also recorded in this table)
- lat: latitude
- lon: longitude
- coordinate_reference_system: e.g. "WGS 1984"
- coordinate_format: e.g. "Decimal Degrees"
- shape: PostGIS-representation of the shape that can be accessed with a PostGIS query
- <OBJECT>_POLYLINE: contains all the data related to polylines defined on the object. The individual points making up the polyline are stored in the <OBJECT>_POINT table, but the polyline object is additionally stored in the <OBJECT>_POLYLINE table. The main column is shape, a PostGIS-representation of the shape that can be accessed with a PostGIS query.
- <OBJECT>_POLYGON: similar to <OBJECT>_POLYLINE, but for polygon objects.
A series of database views are pre-defined on the staging area, three for each object: <OBJECT>_POINT_VIEW, <OBJECT>_POLYGON_VIEW and <OBJECT>_POLYLINE_VIEW - where <OBJECT> is HAZARD, GAZETTEER, MRE, etc. - each object that potentially has associated geodata. Each view is defined as an INNER JOIN between the <OBJECT> table, e.g. HAZARD, and each of the three geodata tables. The inner join means that data from e.g. the HAZARD table that has no polygon associated will not be found in the HAZARD_POLYGON_VIEW. Depending on the use case, either the tables or the views can be accessed.