Working group III: Vertical datum

SIRGAS-WGIII (Vertical datum) was established during the IAG Scientific Assembly held in Rio de Janeiro in 1997. Its main objectives are to define a modern unified vertical reference system for SIRGAS, to establish the corresponding reference frame, and to transform the existing classical height datums to the new system. As a fundamental SIRGAS-WGIII activity a diagnostic of the existing height datum was carried out, the main conclusions are:

  1. The reference level of the Latin American height datums is realized by the mean sea level registered at individual tide gauges over different periods, i.e. they refer to different epochs,
  2. The vertical networks were extended over each country using mainly spirit levelling methods, but in general the levelled heights have not been corrected by the gravity effects,
  3. They do not take into account the variation of heights and reference levels with time, i.e. they are static, and therefore
  4. These vertical datums present big discrepancies between neighbouring countries, they do not permit data exchange neither in continental nor in global scale, and they are not able to support practical height determination with GNSS techniques in combination with precise geoid models.

The definition of the new SIRGAS vertical reference system is identical with the definition of the International Height Reference System (IHRS) given by the Resolution No. 1, 2015, of the International Association of Geodesy (IAG). The realization of the new SIRGAS vertical reference system must be a regional densification of the International Height Reference Frame (IHRF). The geometrical component corresponds to ellipsoidal heights referred to the SIRGAS reference frame. The physical component is given in terms of geopotential quantities (W0 as a reference level and geopotential numbers as primary coordinates), and its realization should:

  1. refer to the conventional W0 value adopted by Resolution No. 1, 2015 of the IAG, 
  2. be given by proper physical heights (derived from spirit levelling in combination with gravity reductions or by gravity field analysis of high-resolution), and
  3. be associated to a specific reference epoch, i.e. it should consider the coordinate and referential changes with time.

Members of the SIRGAS-WGIII

Gabriel do Nascimento Guimarães (gabriel @, Chair, UFU, Brazil
Silvio Rogério Correia de Freitas (sfreitas @, UFPR, Brazil
Melvin Hoyer (melvinhoyer @, LUZ, Venezuela
Oscar Carranco (oscar.carranco @, IGM, Ecuador
Jorge Faure Valbi (jfaure @, UDELAR, Uruguay
Norbertino Suárez (norbertinosuarez @, SGM, Uruguay
Vagner Gonçalves Ferreira (vagnergf @, Hohai University, China
Karoline Paes Jamur (kjamur @, UFPR, Brazil
Roberto Teixeira Luz (roberto.luz @, IBGE, Brazil
Nivia Regis Di Maio Pereira (nivia.maio @, IBGE, Brazil
Juan Francisco Moirano (jmoirano @, UNLP, Argentina
Henry Montecino Castro (henrymontecino @, UdeC, Chile
Ana Crisitina Oliveira Concoro de Matos (acocmatos @, USP, Brazil
Hernán Guagni  (hguagni @, IGN, Argentina
José Luis Carrión Sánchez (josecarrionsa @ , IGM, Ecuador
Leidy Johanna Moisés Sepúlveda (leidydumoises @, IGAC , Colombia
José Antonio Tarrío Mosquera (jose.tarrio @, Universidad de Santiago, Chile
Maria Marta Mora Rivas (mmorar @, IGN, Costa Rica
Andrea Galudht Santacruz Jaramillo (andreasantacruzj @, UFPR, Brazil

Past chairs

Silvio Rogério Correia de Freitas (2013 - 2019), UFPR, Brazil
Roberto Texeira Luz (2008 - 2013), IBGE, Brazil
William Martínez Díaz (2007 - 2008), IGAC, Colombia
Laura Sánchez (2001 - 2007), IGAC/DGFI, Colombia/Germany
Roberto Texeira Luz (1997 - 2001), IBGE, Brazil

Follow us