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Point

Description: 

 Name                            Null?    Type
 ------------------------------- -------- ----
 LOCALITY_ID                     NOT NULL NUMBER
 LATITUDE_DEGREES                         NUMBER(5,2)
 LATITUDE_MINUTES                         NUMBER(5,2)
 LATITUDE_SECONDS                         NUMBER(5,2)
 LATITUDE_DIRECTION                       VARCHAR2(1)
 LONGITUDE_DEGREES                        NUMBER(5,2)
 LONGITUDE_MINUTES                        NUMBER(5,2)
 LONGITUDE_SECONDS                        NUMBER(5,2)
 LONGITUDE_DIRECTION                      VARCHAR2(1)
 ACCURACY                                 NUMBER
 ELEVATION                                NUMBER
 DATA_SOURCE                              VARCHAR2(10)
 ELEVATION_MAX                            NUMBER
Primary Key:
Locality_ID
Foreign Key:
Locality_ID references LOCALITY(Locality_ID)
Collecting localities that are represented by single points in space have their geographic coordinates stored in this table. Obviously, there is some arbitrary decision involved here as to the amount of area one is willing to refer to as a point. This decision will depend upon the scale of a particular study. We are interested in rather large-scale problems, hence we are willing to accept a town, village, or city as a point.

The same Locality_ID serves as the primary key in the Geometric_Locality and Locality tables.

The values for latitude and longitude at their three levels should have a not null constraint. Otherwise, when I try to do arithmetic on them (such as to calculate decimal degrees), entries with any null values are ignored. At present we're dealing with this by putting zeros in the seconds field when we have only degrees and minutes.

The Latitude_Direction field contains either 'N' or 'S'; Longitude_Direction contains either 'E' or 'W'. These are then decoded as +/- 1 and multiplied by the calculated value for decimal degrees for input into ARC/INFO.

Accuracy is included for GPS recorded points. I have also heard of subjective codes (I suppose they could be objective) being used to indicate the relative degree of precision of a set of geographic coordinates. Two fields are available for elevation when it is expressed as a range. Our values for Data_Source are

Last updated: 20 November, 1997 by nfj.