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CDR & Tower Triangulation Timeline

Run the CDR & Tower Triangulation MicroSim Fullscreen

About This MicroSim

Every call a phone makes is logged in a Call Detail Record (CDR): the time, the call type, the duration, and the cell tower that carried it. Because each tower covers a known area, an investigator can place a device on a map at each moment and reconstruct its movement over time.

This MicroSim pairs a coverage map (left) with a CDR table (right). Play the timeline to watch the device travel between towers in chronological order, then turn on the trilateration overlay to see how three tower ranges pin down an estimated location with an uncertainty radius.

How to Use It

  1. Read the CDR table — the rows are in time order, each naming the tower that handled the call.
  2. Click a row to highlight that tower (green) on the map.
  3. Press ▶ Play Timeline to animate the orange device icon along its path; adjust the Playback speed slider as needed.
  4. Press Show Triangulation to display three range circles from three towers converging on the estimated location, with the ranges (in metres) and the uncertainty radius.

What You Can Learn

  • Use CDR rows (time and tower ID) to order a device's tower contacts.
  • Reconstruct geographic movement by mapping those contacts over time.
  • Apply trilateration to estimate a location from three tower ranges and state its uncertainty.

You can embed this MicroSim on your own web page with this iframe:

<iframe src="https://dmccreary.github.io/forensic-science/sims/cdr-tower-triangulation/main.html"
        width="100%" height="517" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 20–25 minutes Bloom level: Apply (L3) — use.

Worked example. Have students list the seven tower contacts in order, then predict the shape of the path before pressing Play. Compare their sketch to the animated route.

Guided questions:

  • Between 09:35 and 09:52 the device jumps from tower B-204 to C-073. Roughly how far did it travel, and how fast must it have moved?
  • With Show Triangulation on, why do three circles give a single estimate while two would leave an ambiguity?
  • What does the uncertainty radius represent, and what would shrink it?

Extension. Discuss why a single tower contact only proves the device was somewhere in that tower's coverage, not at the tower — a common misinterpretation in court.

References

Specification

This MicroSim was generated from a specification in Chapter 17: Cell Phone Analytics and Mobile Forensics.

Design note: towers, coverage radii, CDR rows, and the trilateration estimate are illustrative sample data for teaching the method, not real network data. The map spans about 5 km across to give an approximate metres-per-pixel readout. The "export a text timeline" requirement from the spec is represented on-canvas by the chronological timeline bar rather than a file download. Trilateration is drawn geometrically: three range circles are sized to pass through the estimated point so they converge cleanly.