Republic of Colombia Clifford J. Mugnier, C.P., C.M.S.

The contents of this column reflect the included 5 invar baselines, 133 Venezuela is apparently stable; views of the author, who is responsible geodetic stations, 12 astro it is straddled largely by a for the facts and accuracy of the data presented herein. The contents do not stations, and “the ellipsoid continuous chain of necessarily reflect the official views or normal is coincident with the quadrilaterals. However, the policies of the American Society for direction of the plumb line.” territorial limits of the sea seem Photogrammetry and Remote Sensing and/or the Louisiana State University In 1946, the country to be in dispute, particularly Center for GeoInformatics (C4G). was divided into four tangent with respect to fishing rights. meridian belts, each belt three Other datums that exist The City of Santa Fé de degrees wide as measured from in Colombia (at least Bogotá was founded in 1538, the the observatory. For each belt, theoretically) include the region Gran Colombia (modern the False Eastings and False Provisional South American Panamá, Colombia, Venezuela, Northings are equal to 1,000 Datum of 1956 (PSAD 56) and and Ecuador) achieved kilometers each at the the South American Datum of independence from Spain in intersections of the central 1969 (SAD 69). Both PSAD 56 1819 and reorganized as a meridians (λo) and the latitude of and SAD 69 seem to be largely republic in 1886. The Instituto the observatory. The belts are ignored by Colombia although Geográfico Militar was founded lettered as “B” (Bogotá), “Ec” both datums are extended into in 1935 and later renamed in (East central or Este central), other countries through 1950 as the Instituto Geográfico “E” (East or Este), and “O” Colombia and are extensively “Agustín Codazzi” - IGAC, the (West or Oeste). There may be used elsewhere. The majority national mapping agency of a new belt “OO” (Western West network of Colombia, which had Colombia that is responsible for or Oeste Occidente) to cover consisted of 21 fixed stations all civilian and military Isla del Malpelo in the Pacific and 679 adjustable stations, was mapping. The cartographer, Ocean and Isla de San Andrϑs adjusted to the SAD 69 in 1972. Agustín Codazzi, produced early in the Caribbean Sea. The However, a free adjustment was nineteenth century maps of Gran projection system used in also done in 1972 to the total Colombia. In fact, these famous Colombia by definition is the network, which consisted of 1 maps have even appeared on Gauss Conform Transverse fixed station and 950 adjustable Venezuelan postage stamps. Mercator, a particular truncation stations. This free adjustment Furthermore, IGAC provides of the Gauss Schreiber which appears to be the system training services in the mapping was used in the U.S. for the currently in use under the sciences for many Latin North American Datum of 1927. original name of the Bogotá American countries, a service The boundary treaty Datum of 1941. The World previously provided solely by between Colombia and Panamá Geodetic System of 1984 datum the U.S. Inter American was ratified and mutually is used extensively in Colombia, Geodetic Survey (IAGS). exchanged on 31 January 1925. albeit just a tool to extend the The first classical There is no indication of the classical datum. geodetic datum established in geodetic datum used to provide In 1980, IGAC Colombia is the Bogotá Datum the geodetic coordinates listed to established a special “city grid” of 1941. The defining a tenth of an arc second. projection for the City of Santa parameters are referenced to the Fortunately, the fourteen Marta, the oldest city in International ellipsoid (also boundary points are physically Colombia (1525). This special called the Hayford 1909 and the marked and are presumably system was similar in philosophy Madrid 1924) where recoverable. to the systems developed for 1 a = 6,378,388 meters, /f = 297, The boundary history counties in Wisconsin and with an origin of φo = 4° 35’ between Colombia and Brazil is Minnesota for the convenience 56.57”N, λo = 74° 04’ 51.30”W, considerably older, dating back of the local surveyors and GIS and ho = 2,633.6 meters, to 1494. The latest treaty with applications. Specifically, this corresponding to the National Brazil was signed in 1928, but “city grid” was established at a Astronomic Observatory in the coordinates of the boundary particular elevation that Bogotá as of 1935. The azimuth markers were not published until corresponded to the average to station Suba, αo = 359° 1946, presumably on the Bogotá elevation of the city. Local 30’10.0”, and the initial defining Datum of 1941. surveyors could then ignore the adjustment of the datum The land boundary with reduction to sea level correction

when transferring measured field system was reversed back to the identical results. We commonly distances to the city maps. The standard national coordinate use such systems for analytical system was still based on the system in 1994, while other rectification projects if the Gauss Conform Transverse cities were published with their project area is free of relief such Mercator, but the False Eastings own special plane coordinate as a plateau or a flood plain. and False Northings were systems such as Villavicencio Note that these new city modified by truncating to only 1994 (450 meters), Leticia 1994 systems were orthophoto five digits from the observatory (100 meters), and Armenia 1995 projects and not just rectified at Bogotá. (1,470 meters). photos. Grids used in Colombia The reference ellipsoid Although the without special modifications to (International) was modified to Colombian definition uses the the ellipsoid include the Ciudad have its semi-major axis Gauss Conform Transverse de Bogotá (City) Grid and the increased by 29 meters, Mercator for these systems, the Ciudad de Medellín (City) Grid. corresponding to the average Local Space Rectangular The Grid System used for the elevation of the city above mean sometimes used in analytical Ciudad de Cartagena is the sea level determined at photogrammetric calculations standard “B” belt of the National Buenaventura. Curiously, the could just as easily be used with System.

PE&RS November 1997