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How does the PostGIS St _ asmvtgeom function work?
Among them, the ST_AsMVTGeom allows to transform a geometry into the coordinate space of a tile (typically 4096×4096). Given a geometry containing consecutive points that falls onto the same coordinate after transformation, does the function perform simplication on the fly, or should the ST_Simplify function be called beforehand?
Which is more efficient St _ dump or St _ geometryn?
If you want to extract all geometries, of a geometry, ST_Dump is more efficient, and also works for singular geoms. Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.
How to return a simplified version of a given geometry?
Returns a “simplified” version of the given geometry using the Douglas-Peucker algorithm. Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry.
How to return nth geometry in St _ geometryn?
ST_GeometryN — Return the Nth geometry element of a geometry collection. Return the 1-based Nth geometry if the geometry is a GEOMETRYCOLLECTION, (MULTI)POINT, (MULTI)LINESTRING, MULTICURVE or (MULTI)POLYGON, POLYHEDRALSURFACE Otherwise, return NULL Index is 1-based as for OGC specs since version 0.8.0.
How to check the geometry of a table in PostGIS?
Scans all tables with PostGIS geometry constraints and adds them to the geometry_columns table if they are not already there. Also give stats on the number of inserts, already present, or possibly obsolete columns. ST_SetSRID(geometry, integer)
How to use bounding box comparison in PostGIS?
This function call will automatically include a bounding box comparison that will make use of any indexes that are available on the geometries. To avoid index use, use the function _ST_Touches. NOTE: this is the “allowable” version that returns a boolean, not an integer.
How to get a simplified version of a geometry?
ST_Simplify — Returns a simplified version of a geometry, using the Douglas-Peucker algorithm. Returns a “simplified” version of the given geometry using the Douglas-Peucker algorithm. Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry.