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Lecture

Satellite Localization: Projections and Transformations

In course

ENV-340: Fundamentals of satellite positioning

Bases des références géodésiques, principe de mesure utilisé en localisation par satellites et de l'estimation de la qualité de positions GNSS (Global Navigation Satellites Systems). ...

Description

This lecture covers the theory behind satellite localization, focusing on projections and transformations. The instructor explains the principles of map projections, the Swiss projection system, and the challenges of transitioning between different coordinate systems. The session also delves into the importance of understanding geodesy and cartography in GPS measurements, highlighting the impact of map distortions on distance calculations. Additionally, the lecture explores the concept of fixed points in geodetic surveys and the role of transformation services in coordinate calculations. Practical examples and demonstrations help students grasp the complexities of spatial data representation and analysis.

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Instructor

Pierre-Yves Gilliéron

He graduated in Surveying Engineering at the Swiss Federal Institute of Technology Lausanne in 1988. He started his professional career in photogrammetry and digital mapping. He joined the Geodetic Eng. Laboratory in 1997 where he worked as research scientist on various navigation and satellite positioning projects. Since 2018 he is deputy head of the section in environmental sciences and engineering at EPFL. -- He was member of the board of the swiss institute of navigation (ION-CH), member of the swiss geodetic committee (SGK) and expert in different committees of the swiss road association (VSS).

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Related concepts (13)

Map projection

In cartography, a map projection is any of a broad set of transformations employed to represent the curved two-dimensional surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longitude, of locations from the surface of the globe are transformed to coordinates on a plane. Projection is a necessary step in creating a two-dimensional map and is one of the essential elements of cartography. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent.

Orthographic map projection

Orthographic projection in cartography has been used since antiquity. Like the stereographic projection and gnomonic projection, orthographic projection is a perspective (or azimuthal) projection in which the sphere is projected onto a tangent plane or secant plane. The point of perspective for the orthographic projection is at infinite distance. It depicts a hemisphere of the globe as it appears from outer space, where the horizon is a great circle. The shapes and areas are distorted, particularly near the edges.

Equal-area projection

In cartography, an equivalent, authalic, or equal-area projection is a map projection that preserves relative area measure between any and all map regions. Equivalent projections are widely used for thematic maps showing scenario distribution such as population, farmland distribution, forested areas, and so forth, because an equal-area map does not change apparent density of the phenomenon being mapped. By Gauss's Theorema Egregium, an equal-area projection cannot be conformal.

Mercator projection

The Mercator projection (mərˈkeɪtər) is a cylindrical map projection presented by Flemish geographer and cartographer Gerardus Mercator in 1569. It became the standard map projection for navigation because it is unique in representing north as up and south as down everywhere while preserving local directions and shapes. The map is thereby conformal. As a side effect, the Mercator projection inflates the size of objects away from the equator. This inflation is very small near the equator but accelerates with increasing latitude to become infinite at the poles.

Stereographic map projection

The stereographic projection, also known as the planisphere projection or the azimuthal conformal projection, is a conformal map projection whose use dates back to antiquity. Like the orthographic projection and gnomonic projection, the stereographic projection is an azimuthal projection, and when on a sphere, also a perspective projection. On an ellipsoid, the perspective definition of the stereographic projection is not conformal, and adjustments must be made to preserve its azimuthal and conformal properties.

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Related concepts (13)

Map projection

Orthographic map projection

Equal-area projection

Mercator projection

Stereographic map projection