Four Metres of Accuracy Around a Film Canister

The GPS unit was in the field case with the RDF beacons, and I plugged it in to charge before realizing it still held waypoints from 2019—forty-seven coordinates imported from Dave’s Garmin during a flying trip to Vancouver Island. We’d talked about geocaching the entire flight back, something about hiding caches at rural airports, but I never actually went looking for any of them. Just left the waypoints orphaned in non-volatile memory for seven years.

One cache was 800 metres from the framebuilding co-op. GC3K7M2. Difficulty 2, terrain 1.5, size “small.” After the brazing session I walked over, mostly to see whether GPS coordinates from 2019 still pointed at anything real.

The unit showed an accuracy cone of ±4 metres, which sounds precise until you’re standing in the cone looking for a container small enough to hide. The coordinates were recorded to three decimal minutes—about 1.8-metre precision—but consumer GPS receivers don’t resolve that tight. What you get is a circle of uncertainty, and somewhere in that circle is a camouflaged box the size of a sandwich container.

This is apparently where geocaching stops being navigation and becomes visual pattern recognition. The coordinates get you close. Your eyes do the rest. People call it “cache eyes”—the ability to spot anomalies in natural scenery. A rock that’s slightly too regular. A fence post cap that threads instead of nails. A pine cone cluster that doesn’t shed needles the same way as the others around it.

I didn’t have cache eyes. I had coordinates that insisted I was standing on top of the target, an EPE reading that wouldn’t settle below 3.7 metres, and twenty minutes of staring at a decorative boulder arrangement wondering whether rocks in city parks are supposed to have drainage gaps at the base.

They’re not. The third boulder from the west had a 4-centimetre gap between concrete footing and stone. Wedged inside: a black magnetic film canister, the kind that held 35mm film before digital photography made them obsolete. A nano cache. Just barely large enough for a rolled logbook—tissue-thin paper wound tight inside a waterproof tube.

The logbook had eleven entries, oldest from May 2017. Someone named “TrailMix47” claimed First to Find three hours after the cache went live. The most recent entry was October 2024. I signed with the date and “VE6SLP,” the ham radio callsign that doubles as my geocaching handle because I never bothered creating a separate identity. Used the mechanical pencil stub tied to the logbook with fishing line.

Then I had to put it back. Not approximately back—exactly back. Same orientation, same position relative to the gap, magnetic seal facing inward so condensation doesn’t wick through the closure. Leave No Trace is fundamental to geocaching ethics, except you’re leaving something: the proof you were there, hidden in the logbook for the next finder.

The hobby started May 3, 2000, two days after the U.S. military turned off Selective Availability on the GPS constellation. The removal of SA—Blue Switch Day, May 2, 2000—improved civilian GPS accuracy from deliberately degraded ±100 metres to ±10 metres, tight enough to hide a bucket of trade items and have strangers find it by coordinates alone. The first cache was a black plastic bucket in Beavercreek, Oregon, containing software, videos, books, a can of beans, and a slingshot. The can of beans is now a trackable item—moved from cache to cache with a logging code, its position traced online.

I’d set up direction-finding beacons for meteorite recovery two weeks ago, trying to solve a positioning problem: scatter debris across unknown terrain, transmit coordinates, triangulate recovery zones. That hobby stalled on unpredictability—no way to pre-position sensors for events you can’t forecast. Geocaching inverts the problem. The coordinates are fixed. The containers are already there. You just have to go retrieve the experience someone else cached years earlier.

Two more waypoints were within walking distance. GC4H8K9 turned out to be muggled—geocaching slang for “destroyed by muggles,” non-cachers who find a hidden container and assume it’s trash or a bomb. The coordinates led to a fence rail with a hollow end cap, but the cap was painted over and the fence showed fresh stain. Maintenance crew probably sealed it during spring repairs.

GC2P7V1 was a film canister behind an electrical junction box. Four logbook entries, last signed in 2022. I added the fifth, replaced it, and spent the walk back wondering whether the real appeal is the search or the proof that other people search too. Every signature is evidence that someone else navigated the same uncertainty cone, scanned the same visual field, found the discontinuity you just found.

Forty-four waypoints left on the list. Some are probably gone—archived, muggled, or overgrown. Some might still be there, waiting for the next person to import ancient Garmin data and walk the coordinates just to see what 2019 thought was worth hiding.