Data Element: LATITUDE and LONGITUDE
You are invited to read the definitions of terms used in this data standard.
||Latitude and Longitude|
||A numeric description of a real geographic location on the earth's surface, defined by two coordinate values (latitude and longitude) in decimal degree format. There must be two separate fields, one each for latitude and longitude, but for either to have any value you must have both. In addition, information on the datum and ellipsoid associated with the coordinates is needed (see Use Instructions).|
||Real Number, eight decimal places reserved|
||NNNN.NNNNNNNN, where each N indicates a digit with a value of 0 through 9 or a negative indicator; the number may be positive or negative depending on the location on the globe. The negative sign must come at the beginning of the number. All 8 decimal places may not be needed for less precise data, but at least 5 should be supplied if at all possible. Latitude values require no more than 3 spaces to the left of the decimal place, while longitude values may use up to 4.|
|Recommended Field Name||Latitude: LAT
||Parallels of latitude and Meridians of longitude form the Geographic Reference System. This system treats the globe as if it were a sphere or spheroid. The sphere is divided into 360 equal parts called degrees. Each degree can be further subdivided into 60 minutes, each composed of 60 seconds. The standard origin is where the Greenwich Prime Meridian intersects the Equator and divides the globe into four quadrants: northwest, northeast, southwest and southeast. All points are positive north of the Equator and east of the Prime Meridian, and negative south of the Equator and west of the Prime Meridian. The International Date Line is the divider on the other side of the globe.
Each line of longitude runs north and south and measures the number of degrees east or west of the Prime Meridian. Values range from positive 180 to negative 180 degrees.
Lines of latitude run from east to west and measure the number of degrees north or south of the Equator. Values range from the North Pole, at positive 90 degrees, to the South Pole which is located at negative 90 degrees.
|Historical Data||For information on past versions of this standard, contact the National Data Administrator, Branch of Data and Systems Services, Division of Information Resources and Technology Management.|
Part 270, FW 6, Data Management and Standards, has been superceded by Part 274, FW 2, Establishing Service Data Standards.
These values have been in use for many years and are commonly accepted by professionals working in the fields of cartography, geography, and related sciences.
||These data elements will be used in any new automated system, data set, database, or information application, including new Geographic Information System (GIS) data and applications. These data elements will also be used in any major modifications to existing systems or versions of these data-related items that uniquely identify the latitude and longitude point location(s) of a facility or other entity. While latitude and longitude can also be measured in degrees and seconds, the decimal degree format facilitates the use of locational data in the geographic information system (GIS) software commonly used by Service personnel.
Service staff are strongly encouraged to utilize this data element in existing systems, data sets, databases, and information applications. Where existing systems and data-related items are not in compliance, they should be modified to achieve compatibility and implement this data standard.
The datum and ellipsoid associated with the coordinates also need to be provided. This information impacts the position of the latitude and longitude on the surface of the earth. There are several ways to provide this information, depending on the size of the database and whether or not the data were collected at the same time, in the same manner, etc. In a large and diverse database, it is probably best to set up additional columns for datum and ellipsoid using character fields. Standard abbreviations for datum and ellipsoid (for example, NAD83 for datum or GRS80 for ellipsoid) obtained from a GIS software program or standard geographic reference can be used to simplify the data entry procedures. If preferred, the names can be written out. If these data are not available (for either datum or ellipsoid), please indicate 'unknown' rather than an abbreviation.
For small databases, or data sets containing locational information that was all collected with the same datum and ellipsoid, one reference could be attached noting this information rather than entering the information in each row. This would need to be done in a way that the reference always stays with the data. If it is likely that more locational information will be added, and that the datum and ellipsoid will be different, it would be better to put the information in individual fields associated with each row.
||July 13, 1999|
||January 18, 2011|
||Chris Lett, National FWS GIS Coordinator, Branch of Data and Systems Services, Division of Information Resources and Technology Management.|