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v2007.09.13 - Convex Optimization

v2007.09.13 - Convex Optimization

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370 CHAPTER 5. EUCLIDEAN DISTANCE MATRIX5.13 Reconstruction examples5.13.1 Isometric reconstruction5.13.1.0.1 Example. Map of the USA.The most fundamental application of EDMs is to reconstruct relative pointposition given only interpoint distance information. Drawing a map of theUnited States is a good illustration of isometric reconstruction from completedistance data. We obtained latitude and longitude information for the coast,border, states, and Great Lakes from the usalo atlas data file within theMatlab Mapping Toolbox; the conversion to Cartesian coordinates (x,y,z)via:φ ∆ = π/2 − latitudeθ ∆ = longitudex = sin(φ) cos(θ)y = sin(φ) sin(θ)z = cos(φ)(942)We used 64% of the available map data to calculate EDM D from N = 5020points. The original (decimated) data and its isometric reconstruction via(933) are shown in Figure 90(a)-(d). The Matlab code is inF.3.1. Theeigenvalues computed for (931) areλ(−V T NDV N ) = [199.8 152.3 2.465 0 0 0 · · · ] T (943)The 0 eigenvalues have absolute numerical error on the order of 2E-13 ;meaning, the EDM data indicates three dimensions (r = 3) are required forreconstruction to nearly machine precision.5.13.2 Isotonic reconstructionSometimes only comparative information about distance is known (Earth iscloser to the Moon than it is to the Sun). Suppose, for example, the EDMD for three points is unknown:

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