# Trilateration Position Calc — 3-Point Distance Intersection

> 3-Point Distance Intersection (iPhone/iPad app by Shanghai Sheyuan Network Technology Co., Ltd..)

- Source: https://appshunter.io/ios/app/trilateration-position-calc/id6761745770 (this page in markdown: same URL + `.md`)
- Developer: [Shanghai Sheyuan Network Technology Co., Ltd.](https://appshunter.io/developer/1560626858)
- Category: Utilities
- Price: $1.99
- Age rating: 4+
- Requires: iOS 17.0 · 1 MB
- Languages: English
- Released: 2026-04-08
- Data updated: 2026-07-23
- User reviews in markdown: https://appshunter.io/ios/app/trilateration-position-calc/id6761745770/reviews.md

## What is Trilateration Position Calc?

Built for surveyors, accident reconstructionists, and field engineers who need a quick three-point position solve - not a CAD package, not a desktop tool.

WHAT IT DOES
Solves for a 2D position given three reference points and three measured distances. Uses circle-intersection algebra (two-candidate nonlinear solution) plus a linearized 2x2 reduced system as cross-check. Plots all three reference circles and both candidate solutions on a 2D canvas with tolerance rings and per-anchor distance-error verification.

INPUTS
- Three reference points: (x1, y1, r1), (x2, y2, r2), (x3, y3, r3)
  x, y in any consistent unit (feet, meters, mm - your choice)
  r is the measured distance from each reference point to the unknown
- Tolerance for solution validity (default 0.001)

RETURNS
- Solution 1 and Solution 2 (x, y) from the nonlinear solve
- Linearized solution from the 2x2 reduced system
- Linearized determinant value (flags degenerate / parallel cases)
- Per-solution distance verification: actual vs. expected, error
- Validity flag for each candidate based on tolerance

WHY THIS APP, NOT THE FREE ONES
- Math is shown - both solve methods rendered, not just the final coordinates.
- Visual cross-check - 2D plot of anchor circles, candidates, and tolerance rings.
- Works offline - staking jobs, accident scenes, GPS-shadow zones.
- No login. No ads. No telemetry. No subscription.

PRICING
$1.99. Pay once, own it. Lifetime access on iPhone, iPad, and Mac via Family Sharing.

NOT A SUBSTITUTE FOR
PLS-stamped boundary survey work. Geodetic-grade total stations or RTK GPS for legal coordinates. This is a quick verification tool - not legal-survey-grade equipment.

## Chart rankings

- #170 in Top Paid · Utilities (US App Store)


## Version history (last 4 releases)

### 1.0.3 — 2026-07-01

Added a More Pro Tools section to discover related field calculators.

### 1.0.2 — 2026-05-02

Listing refresh - clarified the description, inputs/outputs, and which standards are referenced. No functional changes.

### 1.0.1 — 2026-04-13

Bug fixes and performance improvements.

### 1.0 — 2026-04-08

No release notes.

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All apps by Shanghai Sheyuan Network Technology Co., Ltd.: https://appshunter.io/developer/1560626858

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-07-23.*