Instituto Brasileiro de Geografia e Estatística

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Geodesy

 ProGriD

The Project for the Geodetic Reference System Change (PMRG) and the National Geospatial Infrastructure Project (PIGN) are pleased to introduce the new Coordinate Transformation Program – ProGriD.

ProGriD, a desktop application that runs in Microsoft Windows, was developed to enable coordinate transformation between the official reference systems used in Brazil: Córrego Alegre, SAD69 and SIRGAS2000. It was conceived to provide geospatial data users with a tool that assists in the transition to SIRGAS2000.

ProGriD represents an advance in coordinate transformation. In general, two geodetic reference systems are related by means of transformation parameters referring to any area covered by them. What parameters cannot transform becomes residuals, which represent the distortions of the geodetic network. ProGriD models these residuals towards a more accurate final result.

ProGriD processes files containing latitude and longitude grid values that enable the direct transformation between Córrego Alegre, SAD69 and SIRGAS2000, following the NTv2 format. The choice for the NTv2 grid is due to the fact that many SIG or GPS computational programs can read this format.

ProGriD performs the transformation of coordinates from the following frames:

  • The 1961 frame of Córrego Alegre, referred to ProGriD as Córrego Alegre (1961).
  • The 1970 and 1972 frames of Córrego Alegre, taken altogether, and referred as Córrego Alegre (1970+1972).
  • The original SAD69 frame, including only the classical network, simply called SAD69 Classical Network.
  • The 1996 frame of SAD69, including only the classical network, called SAD69/96 Classical Network.
  • SAD69 Doppler Technique or GPS.

It is relevant to highlight that for the transformation of coordinates between "SAD69 Doppler Technique or GPS" and "SIRGAS2000" (and vice-versa), ProGriD utilizes the parameters in the Resolution of the President of IBGE number 1, of 25/02/2005 (R.PR 01/05) and, as a consequence, produces the same results obtained by TCGEO program.

These parameters were estimated based on a set of 63 geodetic stations of the Brazilian Geodetic System (SDB) GPS Network. As SGB GPS Network presents a much smaller distortion pattern than those determined by classical methods (triangulation and polygonation), it is not necessary to model distortions because they are a few and homogeneous. These options also accept the Cartesian coordinate format as input and output. The Cartesian coordinates can be selected by users when input coordinates are obtained by GPS or Doppler.

The coordinates from the SGB Doppler stations were established by means of the point positioning method, that is, those coordinates were obtained independently of the classical and GPS networks. The modeling of distortion in this case is not important.

The types of coordinates used, associated to each frame, are:

  • Córrego Alegre (1961): latitude / longitude and UTM (E, N).
  • Córrego Alegre (1970+1972): latitude / longitude and UTM (E, N).
  • SAD69 Classical network: latitude / longitude and UTM (E, N).
  • SAD69/96 Classical network: latitude / longitude and UTM (E, N).
  • SAD69 Doppler Technique /GPS: latitude / longitude / geometric height, Cartesian coordinates (X, Y, Z) and UTM (E, N).
  • SIRGAS2000: latitude / longitude / geometric height, Cartesian coordinates (X, Y, Z), and UTM (E, N).

Many applications of ProGriD resulted from users’ suggestions collected through several surveys in scientific events and through an online questionnaire.

Answers to users’ most frequent doubts can be found in the FAQ of PMRG.