Both the longitude and
latitude on this map seem to be wrong. Longitude is from 4° to 8° east
to west. Latitude is from 12° to 18° south to north. However, Colombia
specifies that its maps measure longitude and latitude from a fundamental
data point at the Bogotá Observatory, which is 4°35'56.570" north of
the equator, and 74°4'51,300 west of Greenwich.
The prime meridian was established as the
Greenwich Meridian at The International Meridian Conference in
Washington, D.C. in 1884. 24 countries ratified the decision, but no
country was required to follow it. Several countries, including
Colombia, use their own datum for maps of their own territory.