0734 Seismic vertices

In any description of seismic data, there is a need to select certain points of importance and give their locations. This is generally important so that the survey can be tied to the earth. With all of the points hidden in arrays, it is hard to do this. In particular, it is impossible to give relationships to other entities in Epicentre. For example, I wish to use the "first" station point of a seismic line as the origin or a local coordinate system, or as the shifted origin of a standard projected coordinate system. In order to do this, I need to instantiate a "vertex" that has the semantics of "first shot point". The only vertices I can find that do this would be seismic_facility_node or earth_position_vertex. The seismic_facility_node doesn't work well, because it requires the instantiation of a seismic_facility (which gives more meaning to the station than is intended). The earth_position_node is defined in terms of interpretation. I.e., it does not carry the proper semantics. I would suggest that a seismic_point be related to a seismic_geometry_set and be given a semantic meaning through a type. This would allow us to instantiate "first station", "last station", "bin set corner ..." points, and other earth points of interest.

Add new entities and relationships

Add entity Seismic_acqusition_vertex with a mandatory relationship to one Seismic_geometry_set. Add entity Seismic_processing_vertex with a mandatory relationship to one Binset_grid. Make both entities subtypes of Technical_object and Earth_surface_point. Add entity Ref_acqusition_vertex to specify the type of array node that the acquisition vertex represents. Add a "be a property of" relationship from Pty_location_2d to the two new vertex entities.

Added objects:
seismic_acquisition_vertex (Entity)
seismic_geometry_set.seismic_acquisition_vertex (Attribute)
pty_location_2d.seismic_acquisition_vertex (Attribute)
seismic_processing_vertex (Entity)
binset_grid.seismic_processing_vertex (Attribute)
pty_location_2d.seismic_processing_vertex (Attribute)
ref_seismic_acquisition_vertex (Entity)

Modify diagrams and uniqueness rules

Modify diagram GPA2 to add the new entities. Modify the uniqueness clause on pty_location_2d to add the relationships to the new vertex entities.

Modified objects:
GPA2:_Seismic_Grids (Diagram)
pty_location_2d.si (Unique rule)