- Description of Coordinates
- Data Entry Protocol
Description of Coordinates
Latitude and Longitude describe the numeric coordinates of locations on the earth. However, the coordinates alone are of limited utility without additional information on accuracy, datum and other metadata. Verbatim localities for all incoming material collected by MVZ personnel should be georeferenced by the collector (preferably using a GPS, if possible). Ideally, the following minimal information should berecorded in original field notes: latitude, longitude, source (e.g., GPS, map, gazetteer), datum, and maximum error (see below for more detail). For localities where only a description is available, the following resources are available to assist with georeferencing:
- Georeferencing Guidelines – Detailed procedures for assigning coordinates and associated metadata to descriptive specific localities (developed as part of the MaNIS, HerpNET, and ORNIS database projects).
- Georeferencing Error Calculator – An online tool for determining the maximum uncertainty surrounding a set of coordinates.
- GEOLocate – A semi-authomated georeferencing web service.
Data Entry Protocol
Orig_Lat_Long_Units: Lat_Long coordinates can be entered in many different formats. The format of the data as they are being entered must be selected in the Orig_Lat_Lat_Units field. Data entered in one format will be translated into other formats by the data entry program. Include as many digits of precision as are provided in the original data.
Decimal degrees: If the original units are decimal degrees, enter data only in the Dec_Lat and Dec_Long fields. Locations South of the equator have negative latitudes and locations West of Greenwich have negative longitudes.
Deg. min. sec.: If the original units are given in degrees minutes and seconds, enter the data into the fields labeled “D”, “M”, “S”, “N/S” and “E/W”.
Degrees dec. minutes: If the original units are given in degrees and decimal minutes, enter the data into the fields labeled “D”, “Min.”, “N/S” and “E/W”.
UTM: If the original units are given in Universal Transverse Mercator coordinates, enter the complete data into the fields labeled “UTM_Zone”, “UTM_EW” and “UTM_NS”. The UTM Zone often is omitted in original data, but can be determined from Higher Geography. The data entry applications currently do not translate to or from UTM coordinates. To calculate UTM coordinates from Lat_Long coordinates, visit DMAP: Transverse Mercator Calculator.
Datum: A geodetic datum describes the size, shape, origin, and orientation of a coordinate system for mapping the earth. Latitude and longitude data referenced to the wrong datum can result in positional errors of hundreds of meters. Therefore, when providing latitude and longitude data, it is important to know from which datum those data are derived. Most GPS units allow you to select the geodetic data from which its coordinates will be determined (default usually set to WGS84, but this should be checked in the field). Maps and gazetteers generally provide this information as well. For a detailed description of geodetic datums, visit GISGeography: Geodetic Datums.
Lat_Long_Ref_Source: This field is designed to hold information about the reference source (e.g., map, gazetteer, or software) used to determine the coordinates. Such information should provide enough detail so that anyone can locate the actual reference that was used (e.g., name, edition or version, year).
Max_Error_Distance and Max_Error_Units: These fields are used to describe the accuracy of the coordinate determination. The maximum error is the radius of a circle describing the a horizontal (as opposed to elevational) distance within which the location must lie. If the source geodetic datum for a set of coordinates is not known, but the locality is well-described, the maximum error should be set at 500 meters. Maximum Error is often given with modern GPS units and should be recorded in the field along with the geodetic datum and coordinates.
Nearest_Named_Place and Lat_Long_For_NNP_fg: Localities sometimes include coordinates for a named place rather than for the actual collecting locality. The Nearest_Named_Place field is meant to hold the name of the place to which the coordinates refer, and the Lat_Long_For_NNP_fg field is a yes/no field that flags the coordinate as referring to the nearest named place.
Example: near Stockton
In this case, the NNP is “Stockton,” the Lat_Long_For_NNP_fg = “yes,” and the lat/long coordinates will refer to Stockton.
Example: Rd. 32, outside Stockton
Same as above, except in this case “Rd. 32” can’t be located on a map or gazetteer.
Field_Verified_fg: This field is meant to flag the coordinate record as having been measured or verified in the field with a GPS device. For coordinates where source = GPS, the Field_Verified_fg should always be “yes.”