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GRID ESTIMATION. APLICATION TO DATUM DISTORTION MODELLING. Javier Glez. Matesanz Adolfo Dalda Mourón Instituto Geográfico Nacional. National Network using Spatial Techniques. ED50-ETRS89 Differences. REGENTE. (Regidor 2001). Low Order Network. Objective:
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GRID ESTIMATION. APLICATION TO DATUM DISTORTION MODELLING Javier Glez. Matesanz Adolfo Dalda Mourón Instituto Geográfico Nacional
National Network using Spatial Techniques ED50-ETRS89 Differences • REGENTE (Regidor 2001)
Low Order Network • Objective: • Predict datum changes in the low order network
Objectives • One transformation • Simple to apply • Friendly for any spatial information data user • Efficient, capable of transforming great amounts of data • SIG funcionality • Capable of imitate a re-adjustment of a network, changes in shape and systematic effects. • Removing distortions due to regional perturbations of local geodetic networks (Collier 1992)
7Parameters transformation • Spatial Coord. • Geoidal model • Heterogeneity • 2 areas: • NW • rest
7 PARAMETER • Difficulties finding unique transformation • Simply to apply. Geoid • Efficient
Polynomial transformation • Real and complex variables • Heterogeneous behavior absorbing • Unique transformation • Regression models controls
Polynomial transformation • Complex variable
Polynomial transformation Real variables
Polynomial transformation • Comparison • Truth “REGENTE” • Complex V. • Real V.
Distortion modelling Prediction
Minimum Curvature Surface method • Metal plate behaviour • Soft surface
Minimum Curvature Surface method Ie. NADCON
Rubber Sheeting method • T. Delaunay • Ie Great Britain
Rubber Sheeting method • T. Delaunay. • Virtual points needed to allow linear behaviour out of the border
Least Squares Collocation • Mmcc prediction • Signal estimation • Ax=K+s+n • Ie Australia, Canada Longitude Covariance
TEST AREA (Castilla La Mancha) (JSSobrino 2002) • Readjustment of low order network in ETRS89 • ~1400 external points. Not taken into account to build the tree grids
Comparison • Test Castilla La Mancha • Overall goodness of fit
Points < 25cm MCS LSC Rubber Sheeting