Córrego Alegre Datum The State of Art of their Existence or Not

Abstract

The evolution of the Geodetic Reference Systems (GRS), in Brazil, led, over time, an improvement in quality and
production of systematic data. These systems include: System Stream Alegre, SAD 69 and, from 2014 (although it is
already being used), the SIRGAS (IBGE, 2010). With these systems, is possible locate, spatially, any object or feature
on the earth’s surface. Each system is defi ned by adoption of a reference ellipsoid, oriented, positioned and adjusted
to planet’s dimension. By adopting an GRS, between the necessary procedures for the development of works, is the
implementation of a source, established as a starting point for development of any georeferencing work, called Datum.
Historically the Brazil has adopted, as a geodetic reference for its territory, the following Horizontal Date: Córrego
Alegre; Astro Datum Chuá; SAD 69; SIRGAS 2000. To establish a GRS, at the time of fi rst Datum in Brazil (The Córrego
Alegre), several adjustments were needed to defi ne this system. Before the technological advent of computation,
these adjustments were made with mechanical calculators and the use of boards of logarithms. With this technology,
the “Córrego Alegre Datum of 1949” was established. The choice of the vertex of Córrego Alegre for Datum point,
as well, the international ellipsoid of Hayford for mathematical reference surface, was based on astronomical determinations
made in the implementation of the triangulation chain in Santa Catarina. Its specifi cations were defi ned by
the former National Council of Geography. The original point is located near the city of Frutal, MG, next to BR-153,
which connects Frutal to Prata, MG and, according to the Report of Geodetic Station of IBGE, 1969 - Description of
Triangulation’s Vertex - whose recognition was conducted in 1965, by the 2nd Survey Division of the Brazilian Army,
consists said the vertex was destroyed. But, in recent fi eld work, these authors conducted investigations that may suggest
that that vertex still exists. The present work wants: restate what was found in the fi rst version of research, and with
results presented in a Congress in 2013; present what was found in 2014 ,on the spot, using GPS system equipment
with better precision; confi rm what the IBGE has been found, in recognition held in place, motivated by information
gathered by this research. The Córrego Alegre Datum of 1949 is still part ,of a large number, of systematic topographic
mapping of the Brazilian territory, used and studied in disciplines, such as Cartography, for courses in Geography, in
Cartographic Engineering, Surveying Engineering, and others. To these considerations, must be added that, besides this
monument should already be part of the Historical Cartography of our country, the same, confi rming their existence,
remains in very poor preservation and maintenance conditions. In order to communicate the cartographic community,
this research will seek confi rmation, or not, of the existence of the mark, and alert to the need to preserve a National
Historical Patrimony.