Batch geocoding is used to find the geographic coordinates corresponding to textual identifiers, such as addresses or telephone area codes, for given locations. The resulting coordinates are often used in mapping programs and geotagging. Although geocoding can be performed one address at a time, batch geocoding programs make it much quicker and easier to convert a large number of addresses, or other textual identifiers, into geographic coordinates simultaneously.
There are several software and web-based batch geocoding programs available, some for free. Most require the user to manually enter all the desired locations, then — once the user instructs the program to run — it converts the information to geographic coordinates, generally latitude and longitude. Some programs are also capable of reverse geocoding, which takes the geographic coordinates — retrieved from a Global Positioning System (GPS), for example — and converts them to a street address or other form of identification.
Latitude and longitude coordinates are the most common output of geocoding, but quite a few geocoding systems exist. Depending upon the intended use of the coordinates, other output formats may be more desirable. With Geographical Information Systems (GIS) mapping software, the Universal Transverse Mercator (UTM) or Natural Area Code (NAC) coordinate systems are often used, so a user may want geocode data in UTM or NAC coordinates. Quarter Degree Grid Cells (QDGC) and C-squares are common systems for spatial indexing, which is useful for mapping geographical statistics, such as population density.
Geographic coordinates can usually be imported into a GIS program in the form of a text file, and the program is able to locate the points on a map, as long as they are in the correct coordinate system. Data obtained from a batch geocoding program has a multitude of uses in GIS. For instance, the coordinates could be all the points within a given area, in which a certain pollutant had been detected. Using the geocode data, other spatial information, and the tools available in the GIS program, the most likely sources of the pollutant could then be determined.
Another use of coordinates obtained from geocoding is geotagging, or adding geographical information to the metadata of media files. This often takes the form of reverse geocoding. For example, some digital cameras can be linked to a hand-held GPS unit. Batch geocoding can be used to convert the coordinates recorded by the GPS to an address or place name, thus identifying the location at which each picture from that camera was taken.