Map locations are interpreted as the spatial location of some entity of interest. This object is useful for representing one, or a few locations. See also the 217-MAP-LOCATION-SET object referenced from object types using a large number of locations. Any attribute that is present is assumed to be valid.
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 object contains five distinct locations. The I-th location is encoded as the I-th value of the X-COORD, Y-COORD and Z-COORD attributes. Suppose that a position uncertainty, or tolerance value of 5.0 meters is to be associated with the first, second, fourth and fifth values of the Z-COORD attribute, and that no uncertainty is known for the third Z value. This would be represented by encoding five values for the Z-COORD-UNC:
| Uncerntainty Encoding Example | |
|---|---|
| Element Number | Uncertainty Value with Unit |
| 1 | 5.0 (m) |
| 2 | 5.0 (m) |
| 3 | {absent value} (m) |
| 4 | 5.0 (m) |
| 5 | 5.0 (m) |
As always, absent or null values are represented using a value that 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 third Z-COORD was exact. This could be represented by encoding /the third Z-COORD-UNC value as 0.0 m.
Label |
Restrictions |
Comments |
Optionality |
Units |
|
|---|---|---|---|---|---|
| LONGITUDE | R=FDOUBL | 1 | U | ||
| LATITUDE | R=FDOUBL | 1 | U | ||
| X-COORD | R=FDOUBL | 2 | MAND | U | |
| Y-COORD | R=FDOUBL | 2 | MAND | U | |
| Z-COORD | R=FDOUBL | 2 | U | ||
| NODE-ID | R=ULONG | 3 | MAND | ||
| NULL-VALUE | C=1, | R=OBJREF | 4 | ||
| LONGITUDE-UNC | R=FDOUBL | 5 | U | ||
| LATITUDE-UNC | R=FDOUBL | 6 | U | ||
| X-COORD-UNC | R=FDOUBL | 7 | U | ||
| Y-COORD-UNC | R=FDOUBL | 8 | U | ||
| Z-COORD-UNC | R=FDOUBL | 9 | U | ||
LONGITUDE R=FDOUBL U LATITUDE R=FDOUBL U
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.
X-COORD R=FDOUBL MAND U Y-COORD R=FDOUBL MAND U Z-COORD R=FDOUBL U
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 are expected to contain the longitude and latitude, respectively, and angular units must be supplied.
NODE-ID R=ULONG MAND
Unique (within this Geoshare logical file) identifier for each of the map locations; this provides a means by which other objects could refer to points in this 217-MAP-LOCATION.
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 attributes of this object.
LONGITUDE-UNC R=FDOUBL U
A measure of uncertainty associated with the LONGITUDE attribute values. The sender estimates that the actual value is the LONGITUDE value plus or minus the value in LONGITUDE-UNC.
LATITUDE-UNC R=FDOUBL U
A measure of uncertainty associated with the LATITUDE attribute values. The sender estimates that the actual value is the LATITUDE value plus or minus the value in LATITUDE-UNC.
X-COORD-UNC R=FDOUBL U
A measure of uncertainty associated with the X-COORD attribute 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.
Y-COORD-UNC R=FDOUBL U
A measure of uncertainty associated with the Y-COORD attribute 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.
Z-COORD-UNC R=FDOUBL U
A measure of uncertainty associated with the Z-COORD attribute values. The sender estimates that the actual value is the Z-COORD value plus or minus the value in Z-COORD-UNC.
Send questions and comments to
Jim.Theriot@POSC.org
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