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.