Revision as of 05:26, 15 May 2012

This page discusses the Coordinate Reference Systems used in Brazil. It started as an attempt to reach a consensus on the transformation parameters that should be submitted to the "upstream" of open source programs such as proj4, libgeotiff and gdal.

The discussion was held mostly on the brasil@lists.osgeo.org mailing list starting April 25, 2012 (http://lists.osgeo.org/pipermail/brasil/2012-April/000657.html).

Note: Some parts of this document are in Brazilian Portuguese.

The following references are a substancial source of information (in Portuguese), as well as others below:

http://www.ibge.gov.br/home/geociencias/geodesia/pmrg/faq.shtm http://www.ibge.gov.br/home/geociencias/geodesia/param_transf/default_param_transf.shtm

Coordinate Reference Systems used in Brazil

Brazil has used various reference systems. Brazilian law # XXXX determines that, starting from XXXX, the SIRGAS 2000 sistem will be used exclusively.

( O Brasil já utilizou diversos sistemas de referência. A lei XXXX determina que, a partir de XXXX, será adotado unicamente o sistema SIRGAS 2000 )

SIRGAS 2000

Reference:          ???
Note:               Considered identical to WGS84

SAD69 (SAD69 a partir de 1995)

Projection:         longlat
EPSG code:           4618
PROJ string:        '+proj=longlat +ellps=aust_SA +towgs84=-67.35,+3.88,-38.22'
PROJ string (ntv2): '+proj=longlat +ellps=aust_SA +nadgrids=sad96_003.gsb +nodefs'
Reference:          RPR 01/2005 - 25/02/2005 - IBGE 
                      (ftp://geoftp.ibge.gov.br/documentos/geodesia/projeto_mudanca_referencial_geodesico/legislacao/rpr_01_25fev2005.pdf)

SAD69 before 1995 (SAD69 antes de 1995)

Projection:         longlat
EPSG code:          4291
PROJ string:        '+proj=longlat +ellps=aust_SA +towgs84=-66.87,+4.37,-38.52'
PROJ string (ntv2): '+proj=longlat +ellps=aust_SA +nadgrids=sad69_003.gsb +nodefs'
Reference:          Resolução da Presidência do IBGE n° 23, de 21/02/89 (R.PR 23/89) 
                      (ftp://geoftp.ibge.gov.br/documentos/geodesia/pdf/rpr_2389.pdf)

SICAD (Sistema Cartográfico do Distrito Federal)

Projection:         longlat
EPSG code:          ???
PROJ string:        '+proj=longlat +ellps=intl +towgs84=-144.35,+242.88,-33.22'
Reference:          GDF DECRETO 32.575-2010_SICAD-SIRGAS
                      (http://www.terracap.df.gov.br/internet/arquivos/0073607515.doc)
Note:               only valid in UTM 23s zone

Corrego Alegre 1961 (Córrego Alegre 1961)

Projection:         longlat
EPSG code:          5524
PROJ string:        ???
PROJ string (ntv2): '+proj=longlat +ellps=intl +nadgrids=ca61_003.gsb +nodefs'
Reference:          ???

Corrego Alegre 1970-72 (Córrego Alegre 1970-72)

Projection:         longlat
EPSG code:          4225
PROJ string:        '+proj=longlat +ellps=intl +towgs84=-205.57,+168.77,-4.12'
PROJ string (ntv2): '+proj=longlat +ellps=intl +nadgrids=ca7072_003.gsb +nodefs'
Reference:          https://www.mar.mil.br/dhn/chm/download/ita06.pdf (calculated by composing the transformations in the two following documents)
                    ftp://geoftp.ibge.gov.br/documentos/geodesia/pdf/bservico1602.pdf 
                    ftp://geoftp.ibge.gov.br/documentos/geodesia/pdf/rpr_2389.pdf

Chua (Astro Chuá)

Projection:         longlat
EPSG code:          4224
PROJ string:        '+proj=longlat +ellps=intl +towgs84=-143.87,+243.37,-33.52'
Reference:          http://www.topografia.ufsc.br/Geodesia.pdf (unofficial reference)

Summary Table

Name	EPSG	towgs84	towgs84 currently in use by gdal (incorrect)	ntv2 grid from IBGE
SAD69	4618	-67.35,+3.88,-38.22	-57,1,-41	sad96_003.gsb
SAD69 before 1995	4291	-66.87,+4.37,-38.52	-57,1,-41	sad69_003.gsb
SICAD	???	-144.35,+242.88,-33.22	???	-
Corrego Alegre 1961	5524	???	-	ca61_003.gsb
Corrego Alegre 1970-72	4225	-205.57,+168.77,-4.12	-206,172,-6	ca7072_003.gsb
Chua	4224	-143.87,+243.37,-33.52	-134,229,-29	-

Ellipsoids in use

aust_SA

PROJ name:         Australian Natl &  S. Amer. 1969
PROJ string:       '+ellps=aust_SA'
Semimajor radius   a=6378160.0
Flattening         rf=298.25
EPSG name:         GRS 1967 Modified 
EPSG code:         7050

intl

PROJ name:         International 1909 (Hayford)
PROJ string:       '+ellps=intl'
Semimajor radius   a=6378388.0
Flattening         rf=297.0
EPSG name:         International 1924
EPSG code:         7022

Observations

To use the UTM projection, substitute "+proj=longlat" with the desired projection parameter, zone and units for the area of interest For example:

"+proj=utm +zone=23 +south +units=m" for zone 23s

or

"+proj=utm +zone=21 +north +units=m" for zone 21n

NTV2 grids (*.gsb files) are distributed with the Progrid software package from IBGE (ftp://geoftp.ibge.gov.br/aplicativos/transformacao_coordenadas/).

Observações

Para utilizar a projeção UTM, substitua "+proj=longlat" pelos parâmetros de projeção, zona e unidades para a zona de interesse.

Por exemplo, a string do SAD69:

+proj=longlat +ellps=aust_SA +towgs84=-67.35,+3.88,-38.22

Pode ser transformada em

+proj=utm +zone=23 +south +units=m +ellps=aust_SA +towgs84=-67.35,+3.88,-38.22

para uso na zona UTM 23s ou em

+proj=utm +zone=21 +north +units=m +ellps=aust_SA +towgs84=-67.35,+3.88,-38.22

para uso na zona UTM 21n

Comparação entre o método grid (ntv2) e parâmetros towgs84: SAD69 para SIRGAS2000

Os arquivos *.gsb são distribuídos junto com o software progrid do IBGE (ftp://geoftp.ibge.gov.br/aplicativos/transformacao_coordenadas/) e devem ser copiados para a pasta "/usr/share/proj" para esses parâmetros funcionarem com o proj.

AVISO: o proj não dá erro se você esquecer de copiar o arquivo ou errar o nome do arquivo na string de conversão. Cheque os resultados antes de utilizá-los.

Pendências

testar as transformações do tipo grid (ntv2)
preencher os campos marcados com XXXX
completar a documentação dos sistemas de coordenadas
atingir consenso na lista antes de mandar pedidos de correção ou complementação para os desenvolvedores upstream ou para a EPSG.

Difference between revisions of "Brazilian Coordinate Reference Systems"