GeoNames

GeoNames allows you to find the geographic coordinate of locations across the world, by typing the name of a location.

The website is useful to geo-reference your data if the location name is available.

Used by AidData.org to geo-reference foreign aid project locations.

If you have a lot of observations, however, using the web search is costly to do. ArcGIS is equipped with Geonames Tools toolbox that automates search. Another way to get around is to download the entire data of GeoNames. This page lists the zip files each of which contains all the locations in a particular country (see here to understand which file is for which country). This file can then be merged with your data by location name, which does geo-reference your data.

The list of variables (called fields) in the data (taken from the bottom of this page):

geonameid         : integer id of record in geonames database
name              : name of geographical point (utf8) varchar(200)
asciiname         : name of geographical point in plain ascii characters, varchar(200)
alternatenames    : alternatenames, comma separated, ascii names automatically transliterated, convenience attribute from alternatename table, varchar(10000)
latitude          : latitude in decimal degrees (wgs84)
longitude         : longitude in decimal degrees (wgs84)
feature class     : see http://www.geonames.org/export/codes.html, char(1)
feature code      : see http://www.geonames.org/export/codes.html, varchar(10)
country code      : ISO-3166 2-letter country code, 2 characters
cc2               : alternate country codes, comma separated, ISO-3166 2-letter country code, 200 characters
admin1 code       : fipscode (subject to change to iso code), see exceptions below, see file admin1Codes.txt for display names of this code; varchar(20)
admin2 code       : code for the second administrative division, a county in the US, see file admin2Codes.txt; varchar(80) 
admin3 code       : code for third level administrative division, varchar(20)
admin4 code       : code for fourth level administrative division, varchar(20)
population        : bigint (8 byte int) 
elevation         : in meters, integer
dem               : digital elevation model, srtm3 or gtopo30, average elevation of 3''x3'' (ca 90mx90m) or 30''x30'' (ca 900mx900m) area in meters, integer. srtm processed by cgiar/ciat.
timezone          : the timezone id (see file timeZone.txt) varchar(40)
modification date : date of last modification in yyyy-MM-dd format