POSC Specifications: Epicentre Version 3.0 | Logical Data Model |
This extension defines grid convergence at a point on the Earth. This is the angular deviation between the local grid north and true north at a point.
CHANGE ESM2_grid_convergence (*<REMARK> CHANGE ESM2_grid_convergence *) (*<desc> This extension defines grid convergence at a point on the Earth. This is the angular deviation between the local grid north and true north at a point.*) ALTER ENTITY vertex; INVERSE ADD pty_grid_convergence : SET[0:?] OF pty_grid_convergence FOR vertex (*<desc> This defines the difference between grid north and true north at this point. Each value of grid convergence must reference the coordinate system it is defined for.*) (*<verb>have a property of*); END_ENTITY; ADD ENTITY pty_grid_convergence (*<desc> This property defines the difference between grid north and true north at a point. Since grid north is specific to a coordinate system, each value of grid convergence must reference the coordinate system it is defined for.*) SUBTYPE OF (property); data_value : ndt_plane_angle (*<desc> This is the difference between the grid north and true north as defined by ref_north_axis. By convention, the angle is measured with positive degrees to the east and negative degrees to the west of true north.*); vertex : vertex (*<verb>be a property of*); local_coordinate_system : OPTIONAL local_coordinate_system (*<desc> This is the local coordinate system that defines the grid north that is being described.*) (*<verb>describe the grid convergence from*); projected_2d_coordinate_system : OPTIONAL projected_2d_coordinate_system (*<desc> This is the projected coordinate system that defines the grid north that is being described.*) (*<verb>describe the grid convergence from*); UNIQUE si: vertex, local_coordinate_system, projected_2d_coordinate_system, activity; WHERE mse: EXISTS(local_coordinate_system) XOR EXISTS(projected_2d_coordinate_system) (*<desc>Each pty_grid_convergence must reference either a local or a projected coordinate system.*) (*<ruletype>mse*); END_ENTITY; ALTER ENTITY local_coordinate_system; INVERSE ADD grid_convergence_reference : SET[0:?] OF pty_grid_convergence FOR local_coordinate_system (*<desc> This designates the measurements of grid convergence made at various point for this coordinate system.*) (*<verb>be used to measure*); END_ENTITY; ALTER ENTITY projected_2d_coordinate_system; INVERSE ADD grid_convergence_reference : SET[0:?] OF pty_grid_convergence FOR projected_2d_coordinate_system (*<desc> This designates the measurements of grid convergence made at various point for this coordinate system.*) (*<verb>be used to measure*); END_ENTITY; END_CHANGE;