Comment by zardaxian | Hacker News Reader

Comment by zardaxian | Hacker News Reader

I was building an underwater mapping GUI, a quick SCUBA dive to do some testing before the weather closed in whilst at sea in the GBR Australia.

Dropped to 10 meters, set the datum and started swimming, going well until I crossed into a negative quadrant. My beautiful track went haywire/dead.

Then I swam around trying to get back "into" the positive quadrant, I couldn't find it and consequently couldn't get back to the datum. When I surfaced I couldn't see the dive boat!

After some time contemplating my life/coding choices for literally jumping in without thorough testing, I heard the Zodiac inflatable buzzing around the rising waves looking for me.

Back on the boat I discovered that I had only coded it to work in the positive axis from the datum. In the other axis the location was undefined.

The "system doesn't work with negative datum" bug allegedly hit F-16 flight control software, resulting in a plane that would flip upside down on crossing the equator.

They are upside down down there, so it was a reasonable feature.

Right, it was trying to keep them upright. Northerners' bodies aren't designed to work upside down...

You likely already know about inflatable bouys and/or no longer need them, but just in case: https://www.scuba.com/products/scubapro-marker-buoy-orange?v...

Do you normally dive with a compass?

For similar reasons I usually dive with an analog backup gauge.

Hardware projects are so far from my norm, something like this is hard for me to imagine.

What kind of devices are involved in scuba tech like that?

Not much. A floating GPS antenna on a self tensioner, tablet in a housing. And some buggy code :) Good enough for swim lane mapping and preventing holidays (unsearched areas). Another system we worked with used ultrasonic positioning from beacons, very accurate and covert.

Great story and it made me realize that usage of "holiday" is more general than how I thought of it (missing a spot when painting). Which led me to http://www.word-detective.com/2010/12/holiday/

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