Using GPS in the Field
A GPS receiver is the single most useful tool for relocating a productive spot, but it is easy to over-trust. Knowing how a position fix is actually computed, what makes it drift, and how to record a point you can return to will save you long, frustrating walks across the same patch of ground. This page covers the mechanics and the field habits that turn a rough fix into a dependable one.
How a position fix works
Every GPS satellite continuously broadcasts a radio signal that carries the satellite's position and the precise time the signal left it. Your receiver measures how long that signal took to arrive and, because radio waves travel at the speed of light, converts that travel time into a distance. With the distance to one satellite you sit somewhere on a sphere; with three satellites those spheres intersect to pin down a three-dimensional position on Earth, a method called trilateration. In practice a receiver uses a fourth satellite to correct its own clock, which is why four or more satellites in view gives a solid fix. The GPS constellation is arranged so that at least four satellites are visible from virtually any point on the planet, with the satellites orbiting at roughly 20,200 km altitude (per gps.gov).
Accuracy and what degrades it
Most receivers report an estimated position error (EPE) or accuracy radius. Treat this as a confidence estimate, not a guarantee: it tells you the position is probably within that radius, but local conditions can be worse than the number suggests. Under open sky, GPS-enabled smartphones are typically accurate to within about a 4.9 m (16 ft) radius (approximate, per gps.gov). The government broadcasts the signal with a global average user range error of roughly 2 m or better, 95% of the time (approximate, per gps.gov) but gps.gov is explicit that this is not the same as your real-world accuracy, which also depends on satellite geometry, signal blockage, atmospheric conditions, and receiver quality.
Three things degrade accuracy most in prospecting country. First, blockage: canyon walls, steep gullies, dense tree canopy, and overhangs cut the number of satellites your receiver can see and weaken their geometry. Second, multipath, where signals bounce off rock faces, wet ground, or canyon walls before reaching the antenna, arriving late and pulling the fix off. Third, atmospheric conditions, which slow the signal slightly. You cannot eliminate these, but you can recognize when they are at work: a large or jumping EPE, a position that wanders while you stand still, or a fix that disagrees with the terrain you can see.
Waypoints versus tracks
A waypoint is a single saved point, one set of coordinates marking a specific spot such as a find, a pan site, or a parked vehicle. A track (or track log) is the continuous breadcrumb trail your receiver records as you move, a sequence of points with coordinates and often elevation that shows the path you actually walked. Use waypoints to mark places you want to return to exactly; use a track to retrace your route out, document a stretch of creek you worked, or find your way back to the trailhead in poor visibility. The two work together: drop waypoints on what matters and let the track record how you got between them.
Saving a spot and navigating back
To save a spot, stand on it, confirm the EPE has settled to a small value, and record the waypoint. Because a single instantaneous reading can be off, averaging a point helps: hold the receiver steady in one place and let it collect readings over a period before saving, which smooths out short-term wander and yields a tighter position than a quick grab. To return later, select the saved waypoint and use the receiver's go-to or navigate function, which shows bearing and distance to the point. Walk toward it, correcting as the distance counts down, and expect the last few meters to be the least precise, that is where the accuracy radius matters most.
Practical field tips
- Give the receiver a clear view of the sky and let it settle before trusting the first fix, especially after powering on or leaving a canyon.
- Watch the EPE. If it is large or unstable, move to more open ground or wait, rather than saving a point you cannot trust.
- Average important waypoints instead of grabbing a single reading.
- Carry spare batteries or a power bank; cold weather and constant signal searching drain power fast. Keep a paper map and compass as backup.
- Record a track on the way in so you always have a route out.
In Lodester
In Lodester, mark a find or waypoint at your current position to save its WGS84 latitude and longitude. Let your device's accuracy settle before saving so the stored coordinates are as tight as possible. On mobile, use Show on map to open a deep link to the marked point and navigate toward it; on desktop, copy the coordinates to paste into your mapping tool of choice. To return to a spot later, open the saved find or waypoint and use Show on map (mobile) or the copied coordinates (desktop) to head back to the same location.
This page is general field guidance, not legal or safety advice.