2010-04-21 45 -122

Wed 21 Apr 2010 in 45,-122: 45.3404859, -122.3514034 geohashing.info google osm bing/os kml crox

Location

At the edge of a quarry site north of Estacada.

Participants

• Michael5000

Expedition

I drove out to Estacada in lieu of lunch, trying out my new GPS unit for the first time. It was very satisfying to track my approach to the hashpoint. I pulled off the highway near the site, found a trail into a little woods, and got within 90 feet of the target, according to my new gadget, before being blocked by a steep ditch. The hashpoint didn't really look like what I remembered from the aerial image, but in the spirit of testing out the GPS I hadn't brought a printout.

Huh. I went back to the truck and found a gravel road to approach the hash from another direction. When I reached the quarry entrance, though, the GPS was clearly pointing BEHIND me. This seemed weird, but I looped around, determined that the hashpoint was very much in someone's fenced yard, and headed back to town.

Back at a computer, looking at the aerial image again, I could see that the Google Maps version of the hashpoint was definitely not the same as my GPS's version of the hashpoint. I carefully compared numbers, thinking I had perhaps programmed the GPS improperly, but the numbers were all right. I considered that there might have been a hundredth of a second's discrepancy due to rounding, but I double-checked to determine that this would not be significant (it's only about one foot).

Perhaps somebody savvy in the ways of GPS would have already guessed what was wrong, but it took me quite a while to figure. It turns out that my gadget didn't ship with either of the two logical ways of describing longitude and latitude -- either a straight decimal coordinate (eg. 45.500000° N) or coordinates with minutes and seconds (eg. 45° 30' 00.0" N), but rather a bastard child of coordinates with minutes only (eg. 45 30.000" N). So when I had dutifully entered today's latitude, 45° 20' 25.7" N, I was actually telling my GPS to look for 45° 20.257' N. If you've followed me this far, you can understand that this put me off by several hundred feet.

Here's how far off I was: the purple line represents my trek through the woods trying to reach the wrong hashpoint (the red circle).

(The reason I was so far off north/south but only off a little east/west is that the longitude for the hash was -122° 21' 5.05", and 60% of 5.05" isn't as significant as 60% of 25.7")

I'm allocating blame evenly for this failed expedition between my own mucking up of the technology and the GPS manufacturer using a silly default setting. On the positive side, I learned more about my GPS and how to use it. On the negative side, the error kept me from being able to wander around in an old quarry site littered with abandoned equipment and faded old "No Trespassing" signs. What could have gone wrong?

Michael5000 earned the Blinded by Science Consolation Prize by failing to reach the (45, -122) geohash on 2010-04-21 due to problems with the coordinate format on a GPS unit.