Coordinate system of the spatial objects description

Spatial data located in the database under the control of the DBMS has a coordinate system which is determined by the SRID code - the unique identifier of the coordinate system in the database.

The coordinate system of the cartographic view of these data is determined by the EPSG code specified in the corresponding parameter of the DBM file (see  «Customizing options of view of a spatial database»).

In the database for coordinate systems that are EPSG coordinate systems (that is, described in the Internaltional Association of Oil and Gas Producers (formerly European Petroleum Survey Group) database), the SRID code must match the EPSG code.

When reading information from the database, the spatial data is converted to the coordinate system specified in the parameters of the DBM file by the EPSG code. When writing data into the database, the reverse transformation is performed accordingly. Transformation of the metrics of objects from coordinate system of storage (in the database) into the coordinate system of the cartographic view (according to the DBM file) and vice versa is performed by means of the DBMS.

In order to minimize recalculations when working with a cartographic view, it is recommended in DMB-file options to specify the EPSG code of that coordinate system in which the coordinates are stored in the source table of the database. Or, if the source table contains spatial data simultaneously in different coordinate systems (which is highly undesirable), you should specify EPSG: 4326 (WGS84 - World Geodetic System 1984).

Unspecified EPSG code in file DBM will be by default accepted as EPSG: 4326.

If in a database for the field of spatial data of the source table, the code SRID is not defined and thus in DBM file the EPSG code is set into a zero, then the work with such map will be carried out as with the large-scale plan in its own coordinate system. That is, it is considered that coordinates are stored in meters in the local coordinate system, transformations of coordinates between the database and the cartographical view will not be carried out.