Every few months I hear the same claim on trail and in shops: “Boynton Canyon’s vortex scrambles compasses and drains phone batteries.” I’ve been around long enough to know most nav failures are user- or gear-induced, not geology or mysticism. Before we keep repeating this, can we treat Boynton as a controlled field test and settle what’s actually happening to our gear?
What I’m looking for:
- Measurable effects on navigation instruments: baseplate/Brunton compasses, phone magnetometers, GPS receivers (lock time, SNR, HDOP/VDOP), baro altimeters, and watches with IMUs.
- Battery behavior: normal vs accelerated drain with controlled radio states (airplane mode on/off), screen time, and logging apps. Canyons can force phones to transmit at higher power; that’s a mundane explanation, but let’s quantify it.
- Repeatable mitigation: if there is a modest magnetic anomaly, what loadout/settings keep us honest? If not, which common gear confounders are actually to blame?
Proposed community test protocol (simple, repeatable, no lab coat required):
1) Sites: pick 3 points-Boynton “vortex” lookout, a nearby non-vortex red rock bench, and a distant control of similar rock type/elevation.
2) Instruments:
- Analog: 2 different baseplate compasses (different brands/ages) and, if possible, a Brunton or mirrored sighting compass.
- Digital: two different phones with a magnetometer logging app (records µT), one dedicated handheld GPS (log SNR, satellite count, HDOP), and one watch with baro altimeter + compass. Optional: an external BT GPS puck.
3) Setup controls:
- Calibrate phone compasses away from vehicles/benches.
- Place analog compasses on a non-magnetic surface (wood/plastic), chest-high on a carbon or wood trekking pole or plastic tripod.
- Keep a 1 m “no metal” radius: remove phones, knives, camera plates, trekking poles with flick-locks, steel-shank boots, MagSafe cases/rings, hydration hose magnets, watch bands with magnets, earbuds case, belt buckles, etc. You’d be shocked what a MagSafe ring does to a needle at 30 cm.
4) Measurements (2-minute blocks at each site):
- Analog bearings to two distant landmarks (60-120° apart), repeated by two people, then swap compasses.
- Phone magnetometer total field (µT) and heading; record spikes, not just smoothed headings. Note solar azimuth as a cross-check for expected bearing.
- GPS: time-to-fix from cold start, satellite count, SNR distribution, HDOP/VDOP. Save GPX/fit with raw metrics if your device allows.
- Battery: start/finish percentage with screen-on time and radio state noted (airplane mode vs LTE). Repeat both ways.
5) Replicate at all three sites, then post raw logs/screenshots. If anyone can bring a proper gaussmeter/fluxgate (not a novelty “EMF meter”), even better.
Questions for the hive mind:
- Has anyone logged raw magnetometer field strength at Boynton and compared it to a control? Normal Earth field is 25-65 µT; what did you see?
- Any Garmin/Suunto/Coros users with satellite SNR/HDOP plots in-canyon vs out? GNSS multipath from cliffs will explain a lot.
- Geology folks: any published magnetic anomaly maps for the Schnebly Hill/Redwall units there? Iron oxides in sandstone could bias a needle a few degrees locally, but “spinning compasses” seems unlikely.
- Drone pilots: any repeatable IMU/compass calibration failures in that spot versus other canyons with similar walls?
- Practical mitigation: beyond “carry a map and analog compass,” are you leveraging watch IMU headings (gyro-only), sun compass techniques, or external GPS pucks to stabilize nav in multipath hell?
If we find nothing unusual beyond canyon RF and the usual “my phone case is a magnet” problem, let’s stop telling newcomers that Boynton fries gear. If we do find a small but real anomaly, great-let’s quantify it and list the settings and backup tools that make navigation boring again.