1. Tales from the Geodetic Crypt
Andrew Zolnai
Events: 1989 - 1999
(early GIS Day talk)

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. 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. $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. $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