# Understanding Trilateration

#### **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**.

![](https://freegrow-1.gitbook.io/product-docs-kr/~gitbook/image?url=https%3A%2F%2F2885569511-files.gitbook.io%2F%7E%2Ffiles%2Fv0%2Fb%2Fgitbook-x-prod.appspot.com%2Fo%2Fspaces%252FYKyrLLe7cm7ZOhiSB0gg%252Fuploads%252FCXbsURlhTgxNznNe2smr%252Fimage.png%3Falt%3Dmedia%26token%3Dfb991460-6f97-4432-9655-1e72eef351b8\&width=768\&dpr=4\&quality=100\&sign=964e0cbf\&sv=2)

#### **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 |

[<br>](https://freegrow-1.gitbook.io/product-docs-kr/creatorkit_q1/undefined-1/command)


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