12.540 Principles of the Global Positioning System Lecture 02 Prof. Thomas Herring 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 1 12.540 Principles of the Global Positioning System Lecture 02 Prof. Thomas Herring
Coordinate Systems Today we cover Definition of coordinates Conventional "realization "of coordinates Modern realizations using spaced based geodetic systems(such as GPS) 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 2 Coordinate Systems • Today we cover: – Definition of coordinates – Conventional “realization” of coordinates – Modern realizations using spaced based geodetic systems (such as GPS)
Coordinate system definition To define a coordinate system you need to define Its origin③3 component Its orientation(3 components, usually the direction cosines of one axis and one component of another axes, and definition of handed-ness) Its scale(units) 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 3 Coordinate system definition • To define a coordinate system you need to define: – Its origin (3 component) – Its orientation (3 components, usually the direction cosines of one axis and one component of another axes, and definition of handed-ness) – Its scale (units)
Coordinate system definition In all 7 quantities are needed to uniquely specify the frame In practice these quantities are determined as the relationship between two different frames How do we measure coordinates How do we define the frames 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 4 Coordinate system definition • In all 7 quantities are needed to uniquely specify the frame. • In practice these quantities are determined as the relationship between two different frames • How do we measure coordinates • How do we define the frames
Measuring coordinates Direct measurement( OK for graph paper) Triangulation Snell 1600s: Measure angles of triangles and one-distance in base triangle Distance measured with calibrated chain"or steel band(about 100 meters long) Baseline was about 1 km long Triangles can build from small to larges ones Technique used until 1950s 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 5 Measuring coordinates • Direct measurement (OK for graph paper) • Triangulation: Snell 1600s: Measure angles of triangles and one-distance in base triangle • Distance measured with calibrated “chain” or steel band (about 100 meters long) • “Baseline” was about 1 km long • Triangles can build from small to larges ones. • Technique used until 1950s