spatial_index Docstrings

class spatial_index.SpatialIndex

SpatialIndex class

This spatial indexing class provides functions for converting astronomical spatial constraints (cone or convex polygon on the sky) into constraints appropriate for inclusion in SQL DBMS searches. It is assumed that the DBMS tables have been augmented with a spatial index (integer) column at some HTM or HEALPix level and (x,y,z) three-vector coordinates for each record.

cone_search() converts a cone on the sky (RA, Dec, radius) into a pair of SQL fragments that can be added to an SQL statement.

Parameters

  • ra (double, required) – Right Ascension (decimal degrees J2000) of center of search cone.

  • dec (double, required) – Declination (decimal degrees J2000) of center of search cone.

  • radius (double, required) – Radius (decimal degrees) of search cone.

  • mode (integer, optional, default 0 (SpatialIndex.HTM)) – Indexing mode (SpatialIndex.HTM or SpatialIndex.HPX)

  • level (double, optional, default 7) – Depth of the indexing.

  • xcol (string, optional, default 'x') – Column name for sky position three-vector X component

  • ycol (string, optional, default 'y') – Column name for sky position three-vector Y component

  • zcol (string, optional, default 'z') – Column name for sky position three-vector Z component

  • colname (string, optional, default depends on mode and encoding) – Column name for sky position three-vector Z component

  • encoding (string, optional, default depends on mode and encoding) – Column name for sky position three-vector Z component

Returns

  • The return is a dictionary with integer status and two strings

  • index_constraint (specifying the spatial index cells covered) and

  • geom_constraint (an exact filter for the sky region). If the return

  • status is 1, an error_message is returned instead.

polygon_search() converts a convex polygon on the sky into a pair of SQL fragments that can be added to an SQL statement.

Parameters

  • npoly (int, required) – Number of polygon points (greater than or equal to 3)

  • ra (double list, required) – Right Ascensions (decimal degrees J2000) of the polygon points.

  • dec (double, required) – Declinations (decimal degrees J2000) of the polygon points.

  • mode (integer, optional, default 0 (SpatialIndex.HTM)) – Indexing mode (SpatialIndex.HTM or SpatialIndex.HPX)

  • level (double, optional, default 7) – Depth of the indexing.

  • xcol (string, optional, default 'x') – Column name for sky position three-vector X component

  • ycol (string, optional, default 'y') – Column name for sky position three-vector Y component

  • zcol (string, optional, default 'z') – Column name for sky position three-vector Z component

  • colname (string, optional, default depends on mode and encoding) – Column name for sky position three-vector Z component

  • encoding (string, optional, default depends on mode and encoding) – Column name for sky position three-vector Z component

Returns

  • The return is a dictionary with integer status and two strings

  • index_constraint (specifying the spatial index cells covered) and

  • geom_constraint (an exact filter for the sky region). If the return

  • status is 1, an error_message is returned instead.