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Geodetic Tales

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Geodetic Tales

  1. 1. Tales from the Geodetic Crypt Andrew Zolnai Events: 1989 - 1999 (early GIS Day talk)
  2. 2. It’s the datum, stupid • Errors in datums are in the order of meters, much harder to detect that errors in projections in the order of hundreds of meters • US cruise missile that hit the Chinese embassy in Belgrade during the Balkan War, apparently flew down the wrong street • One military group provided the geodetics that were apparently mistranslated by another group in using the wrong datum • Ironically it’s the very small size of the error that made it undetectable
  3. 3. Gentlemen, start your GPS • Soldiers scouted locations in Afghanistan to triangulate targets on the ground, radioed to AWACS above for use by laser-guided bombs • One such troupe came under fire, jumped into a watery ditch, and dropped a GPS unit that reset itself when it short-circuited in the water... • But wait! it then sent its coordinates to the AWACS, not the target’s it had just triangulated... • The laser bomb hit the ditch alright - that’s how precise it was – so the blast went straight up not sideways, and the scouts lived to tell the tale
  4. 4. $100 beats $100M • Air Force and Navy fighter pilots used to play war games over the Arctic, deemed the most likely path for a Cold War-era invasion at the time • The Navy outfitted its jets with radar detectors, the kind you buy for a car at any electronics store • That apparently gave Navy pilots a split-second advantage in detecting Air Force jets first • The upper hand was gained purely based on hardware that was a fraction of the cost of the fighter jets being flown then
  5. 5. $100 crashes $¼B • The space craft carrying a Mars lander flew straight into the Red Planet at full speed • It apparently had miscalculated its altitude by using the wrong conversion parameter • The lesser-known part is, however, that when Ground Control noticed the error, the modem had a glitch and failed to relay the corrections • Anyone who’s used a modem will know how often they simply stop and need rebooting • A $250M mission relied on off-the-shelf hardware to communicate as far as 250M miles