Resumen

OREIRO, Fernando; D'ONOFRIO, Enrique  y  FIORE, Mónica. Altimetric reference connection of nautical charts and WGS84 ellipsoid for the Río de la Plata. Geoacta [online]. 2015, vol.40, n.2, pp.109-120. ISSN 1852-7744.

Depths provided by nautical charts are calculated as the distance between the submarine topography and the Chart Datum (CD). These depths are obtained from soundings that must be corrected for several factors, from which stands out for its magnitude the tidal correction. The tidal correction is traditionally estimated from tidal observations near or within the area of the bathymetric survey. This estimation directly affects the resulting depth and can introduce a significant error in it. Obtaining the tidal correction through the ellipsoidal height that provide Global Navigation Satellite Systems (GNSS) allows to know the distance between the water surface and the CD in the position of the ship, simplifying the calculation and improving accuracy in the tidal correction applied to soundings. However, to apply this methodology, the connection between the CD and the origin of the vertical coordinate of GNSS must have been previously set. The aim of this work is to generate for the Rio de la Plata a model that connect the CD used on charts of Argentine Servicio de Hidrografía Naval, with the reference system that uses the Global Positioning System (GPS), WGS84 ellipsoid, materialized in Argentina through POSGAR07 reference frame. This relation is established through the Mean Sea Level (MSL) surface, modelled on the two reference systems. To select the representation of MSL, referred to the WGS84 ellipsoid, that best fits the Río de la Plata, the global MSL models DTU10MSS and CLS2011 and geoid models EGM2008 and GAR are compared with satellite altimetry observations of Topex/Poseidon, Jason1 and Jason2 missions, to which are applied new tidal and atmospheric effect corrections that allows obtaining, from each observation, the MSL value. The average and standard deviation of the differences of the models and the corrected satellite observations are respectively: EGM2008 (0,40 m, 0,16 m), GAR (0,251 m, 0,22 m), DTU10 MSS (-0,01 m; 0,17 m), CLS2011 (0,00 m, 0,16 m). The Río de la Plata CD and its relation to the MSL are obtained from the information provided by the nautical charts. The connection between the CD and the WGS84 ellipsoid is calculated through the difference between the MSL referred to CD and the MSL model CLS2011 referred to WGS84 ellipsoid, which shows the best fit in the Rio de la Plata. The expected error of the obtained model (0,30 m) is comparable to the maximum permissible error for the depths that are used in nautical charts in the Rio de la Plata. The generated model provides a new link for the area, and is the first step in developing a methodology to obtain the depths of nautical charts from soundings and GPS observations.

Palabras clave : Altimetric references; Chart Datum; WGS84 ellipsoid; Rio de la Plata; Mean Sea Level.

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