title: Computing the Deflection of the Vertical for Improving Aerial Surveys: A Comparison between EGM2008 and ITALGEO05 Estimates.
abstract: Recent studies on the influence of the anomalous gravity field in GNSS/INS applications have shown that neglecting the impact of the deflection of vertical in aerial surveys induces horizontal and vertical errors in the measurement of an object that is part of the observed scene; these errors can vary from a few tens of centimetres to over one meter. The works reported in the literature refer to vertical deflection values based on global geopotential model estimates. In this paper we compared this approach with the one based on local gravity data and collocation methods. In particular, denoted by ξ and η, the two mutually-perpendicular components of the deflection of the vertical vector (in the north and east directions, respectively), their values were computed by collocation in the framework of the Remove-Compute-Restore technique, applied to the gravity database used for estimating the ITALGEO05 geoid. Following this approach, these values have been computed at different altitudes that are relevant in aerial surveys. The (ξ, η) values were then also estimated using the high degree EGM2008 global geopotential model and compared with those obtained in the previous computation. The analysis of the differences between the two estimates has shown that the (ξ, η) global geopotential model estimate can be reliably used in aerial navigation applications that require the use of sensors connected to a GNSS/INS system only above a given height (e.g., 3000 m in this paper) that must be defined by simulations.
authors.affiliation: Department of Civil and Environmental Engineering (DICA), Politecnico di Milano, Milan 20133, Italy. riccardo.barzaghi@polimi.it.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Barzaghi
authors.affiliation: Department of Civil and Environmental Engineering (DICA), Politecnico di Milano, Milan 20133, Italy. daniela.carrion@polimi.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Carrion
authors.affiliation: Architecture, Built environment and Construction engineering (ABC), Politecnico di Milano, Mantova 46100, Italy. massimiliano.pepe@polimi.it.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Pepe
authors.affiliation: Department of Science and Technology (DIST), University of Naples "Parthenope", Naples 80143, Italy. pina.prezioso@uniparthenope.it.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Prezioso
keywords: EGM2008; Least Squares Collocation; aerial surveys; deflection of the vertical