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v2010.10.26 - Convex Optimization

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480 CHAPTER 5. EUCLIDEAN DISTANCE MATRIX5.13 Reconstruction examples5.13.1 Isometric reconstruction5.13.1.0.1 Example. Cartography.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 MatlabMapping Toolbox; 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)(1139)We used 64% of the available map data to calculate EDM D from N = 5020points. The original (decimated) data and its isometric reconstruction via(1130) are shown in Figure 134a-d. Matlab code is on Wıκımization. Theeigenvalues computed for (1128) areλ(−V T NDV N ) = [199.8 152.3 2.465 0 0 0 · · · ] T (1140)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, EDM D forthree points is unknown:D = [d ij ] =⎡⎣0 d 12 d 13d 12 0 d 23d 13 d 23 0but comparative distance data is available:⎤⎦ ∈ S 3 h (880)d 13 ≥ d 23 ≥ d 12 (1141)

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