Geoshare Data Model, Version 13.0

217-MAP-LOCATION-SET

Description    Attributes    Comments    References   

Description

Map locations are interpreted as a spatial location of some entity of interest. This object is useful for representing a large number of locations. See also the 217-MAP-LOCATION object referenced from object types using only a small number of locations.

Measures of uncertainty can be associated with any or all of the values of any or all of the position attributes in objects of this type. As an example of use, suppose that a given 217-MAP-LOCATION-SET object contains fifty distinct locations. The I-th location is encoded as the I-th value of the X-COORD, Y-COORD and Z-COORD attributes in the associated frame data. Suppose that a position uncertainty, or tolerance value of 5.0 meters is to be associated with all but the 22nd values of the Z-COORD attribute, and that no uncertainty is known for the 22-nd Z value. This would be represented by creating and encoding a channel for the Z-COORD-UNC and giving it the following values:

As always, absent or null values are represented using a value that also appears in the 217-NULL-VALUE object for the associated representation - in this case FDOUBL. Suppose instead of having an unknown uncertainty, it were known that the value of the 22-nd Z-COORD was exact. This could be represented by encoding the 22-nd Z-COORD-UNC value as 0.0 instead of the absent value.

The general convention for indicating that the collection of points is a closed loop, or ring, is to use identical values for the first and last points; i.e., the first point is repeated at the end. This convention should be followed regardless of the presence of other attributes to indicate that the set of points is closed. When the first and last points are the same, the NODE-IDs of the two points will also be the same. This will help prevent the location from being stored twice as distinct points in the receiving system.

Description    Attributes    Comments    References   

Attributes

Description    Attributes    Comments    References   

Comments

1. LONGITUDE   C=1, R=OBJREF      
   LATITUDE   C=1, R=OBJREF      
         

   References to CHANNEL objects giving position in terms of longitude and latitude; always in units degrees. Latitudes are positive in the northern hemisphere and negative in the southern hemisphere. Longitudes are positive in the eastern hemisphere, and negative in the western hemisphere.

2. X-COORD   C=1, R=OBJREF   MAND   
   Y-COORD   C=1, R=OBJREF   MAND   
   Z-COORD   C=1, R=OBJREF      
         

   References to CHANNEL objects giving position in terms of X, Y and Z Cartesian coordinates. Z values are depths and hence are zero at the working datum, and increase downward from there. When the LATLONG cartographic projection is used, X-COORD and Y-COORD CHANNEL values are expected to contain the longitude and latitude, respectively, and the unit in the CHANNEL object will be one of the angular units.

3. NODE-ID   C=1, R=OBJREF   MAND   
         

   A reference to a CHANNEL object whose values give unique (within this Geoshare transaction) identifiers for each of the map locations; this provides a means by which other objects could refer to points in this 217-MAP-LOCATION-SET object.

4. NULL-VALUE   C=1, R=OBJREF      
         

   A reference to a 217-NULL-VALUE object defining null or absent values that can be encoded in the data in CHANNELs referenced from this object.

5. LONGITUDE-UNC   C=1, R=OBJREF      
         

   A reference to a CHANNEL object whose values give a measure of uncertainty associated with the LONGITUDE attribute CHANNEL values. The sender estimates that the actual value is the LONGITUDE value plus or minus the value in LONGITUDE-UNC.

6. LATITUDE-UNC   C=1, R=OBJREF      
         

   Reference to a CHANNEL object whose values give a measure of uncertainty associated with the LATITUDE attribute CHANNEL values. The sender estimates that the actual value is the LATITUDE value plus or minus the value in LATITUDE-UNC.

7. X-COORD-UNC   C=1, R=OBJREF      
         

   Reference to a CHANNEL object whose values give a measure of uncertainty associated with the X-COORD attribute CHANNEL values. The sender estimates that the actual value is the X-COORD value plus or minus the value in X-COORD-UNC. When the X-COORD contains a longitude, X-COORD-UNC, if present, may contain uncertainty in longitude, and have angular units, or uncertainty may be in distance and have distance units. The CHANNEL UNIT attribute is the only way to distinguish these cases.

8. Y-COORD-UNC   C=1, R=OBJREF      
         

   Reference to a CHANNEL object whose values give a measure of uncertainty associated with the Y-COORD attribute CHANNEL values. The sender estimates that the actual value is the Y-COORD value plus or minus the value in Y-COORD-UNC. When the Y-COORD contains a latitude, Y-COORD-UNC, if present, may contain uncertainty in latitude, and have angular units, or uncertainty may be in distance and have distance units. The CHANNEL UNIT attribute is the only way to distinguish these cases.

9. Z-COORD-UNC   C=1, R=OBJREF      
         

   Reference to a CHANNEL object whose values give a measure of uncertainty associated with the Z-COORD attribute CHANNEL values. The sender estimates that the actual value is the Z-COORD value plus or minus the value in Z-COORD-UNC.

Description    Attributes    Comments    References   

References

• 217-LAND-NET-LIST
• 217-MAP-POLYLINE
• 217-SEISMIC-LINE
• 217-SURFACE-INTERSECTION
• 217-WELL-TARGET

Geoshare Data Model, Version 13.0

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