Signal Triangulation
Edit on GitHubLocating a beacon from two or three listening points: the bearings, the intersection, and the honest accuracy of the method.
Signal Triangulation
With two or three listening points you can locate a beacon without walking to it: take a bearing from each point, draw the lines, and the intersection is the beacon’s position.
The method
- Point A: note the direction of the strongest signal (rotate the receiver for the peak, or use the SEARCH mode peak).
- Move 100 - 300 m to point B, roughly perpendicular to the first bearing.
- Point B: take the second bearing.
- Draw: on the map, the two bearing lines intersect at the beacon’s position.
The geometry
| Angle between bearings | Accuracy |
|---|---|
| Near 90 degrees | Best: a tight intersection |
| Near 0 or 180 | Useless: the lines are parallel |
| Anything over 30 degrees | Workable |
If the first two bearings are nearly parallel, move to make a wider angle rather than accepting a bad intersection.
The error budget
| Error source | Effect |
|---|---|
| Bearing error of 5 degrees | Hundreds of meters at 1 km range |
| Antenna pattern asymmetry | Systematic bias in one direction |
| Multipath | A bearing pointing at a rock face, not the beacon (see Homing Technique) |
The third point
A third bearing turns the intersection into a triangle. If the three lines do not meet, the triangle’s size is the honest error estimate: a small triangle means a good fix, a large one means the bearings are unreliable.
The honest summary
Triangulation with a handheld is a coarse tool: good for “which valley” or “which slope”, not for “which tree”. For meter accuracy, use the last-100-meters audio technique (see Homing Technique).
Related pages
- Signal Strength Mapping for the RSSI method
- Search Patterns and Procedure for the search
- Coordinate Plotting and Maps for the drawing