Understanding Trilateration
This is a basic concept you must understand before installing the GrowSpace UWB-based RTLS system.
What is Trilateration?
Trilateration is a method of calculating the position of a tag by using the distance between the tag and three or more anchors. This is the most common and accurate method used in UWB indoor positioning systems.
How It Works
1. Tag → Anchor: Signal Transmission
The tag sends a UWB signal.
Surrounding anchors receive this signal.
2. Anchor → Tag: Distance Measurement
Each anchor measures the distance to the tag.
The distance is calculated based on the Time of Flight (TOF), which is the time it takes for the signal to travel.
3. Position Calculation
The distances from three or more anchors are used to calculate the tag position.
The calculation uses the concept of circle intersections.
Example:
If anchors A, B, and C are 3m, 4m, and 5m away from the tag:
Draw three circles centered on A, B, and C.
The point where the three circles intersect is the tag location.
Important Installation Notes
Use at least three anchors
Trilateration does not work with fewer than three anchors.
Enter accurate anchor coordinates (X, Y, Z)
Incorrect coordinates will cause inaccurate RTLS results.
Do not omit the Z coordinate
Position is calculated in 3D space.
Missing the Z (height) value will distort distance measurements.
Minimum distance between anchors: 2 meters
If anchors are too close, calculation accuracy decreases.
Keep tags inside the anchor coverage area
Position accuracy drops near the edges of the installed area.
Practical Example
Anchor Coordinates:
A: (0, 0, 2)
B: (6, 0, 2)
C: (3, 5, 2)
Tag Position:
(3, 2, 1.5) → Calculated using trilateration.
Common Issues and Causes
RTLS position jumps
Too few anchors, wrong coordinates, or obstacles
Distance measured but no position
Less than 3 anchors or missing coordinates
Tag shown outside walls
Asymmetrical anchor placement or tag near edge area
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