Architecture Overview
Relevant source files
The following files were used as context for generating this wiki page:
The geo-path-reducer project is a specialized JavaScript library designed to simplify geospatial curves using the Douglas-Peucker algorithm. Its primary purpose is to reduce the complexity of spatial data, such as paths or trajectories represented by latitude and longitude points, while maintaining the essential shape of the original path based on a user-defined threshold (epsilon).
The architecture is modular, consisting of a core reducer function that orchestrates recursive path splitting, supported by geometric calculation utilities for distance and perpendicularity. This structure ensures that the complex geospatial logic is separated from the recursive simplification flow.
Sources: README.md:1-5, package.json:6
Core Components and Modules
The system is divided into three primary functional modules that handle the reduction logic and the underlying mathematical calculations.
1. Simplification Orchestrator (src/index.js)
The geoPathReducer function serves as the entry point. It implements the recursive Douglas-Peucker logic by identifying the point with the maximum perpendicular distance from a line segment formed by the start and end points of a path.
2. Geometric Utilities (src/distance.js and src/perpendicular-distance.js)
These modules handle the spatial math required to determine if a point should be kept or discarded.
- Great-Circle Distance: Calculates the distance between two points on the Earth's surface using the Haversine formula.
- Perpendicular Distance: Calculates the distance of a point from a line segment using Heron's formula for the area of a triangle.
| Module | Function | Description |
|---|---|---|
index.js | geoPathReducer | Main recursive function for path simplification. |
perpendicular-distance.js | perpendicularDistance | Calculates how far a point is from a line segment. |
distance.js | distance | Calculates great-circle distance in kilometers. |
Sources: src/index.js:3-25, src/distance.js:1-15, src/perpendicular-distance.js:3-11
Logic Flow and Data Transformation
The data flow follows a recursive "divide and conquer" strategy. The library takes an array of geographic points and iteratively splits them into smaller segments until all points within a segment are within the tolerance level (epsilon).
Data Processing Flow
The following diagram illustrates the process of simplifying a path from input to output:
This diagram shows how the algorithm recursively partitions the array based on the epsilon threshold.
Sources: src/index.js:3-25, README.md:21-30
Mathematical Implementation
The distance calculation utilizes the Earth's radius (6371 km) and converts coordinates to radians to calculate the great-circle distance.
// Example of the Great-Circle Distance implementation
const R = 6371; // Earth's radius in kilometers
const dLat = ((lat2 - lat1) * Math.PI) / 180;
const dLon = ((lon2 - lon1) * Math.PI) / 180;
// ... calculation of 'a' and 'c'
const d = R * c;
Sources: src/distance.js:3-14
Component Relationships
The internal modules depend on each other in a linear hierarchy to perform calculations.
This relationship shows that the main reducer relies on perpendicular distance checks, which in turn require basic point-to-point distance calculations.
Sources: src/index.js:1, src/perpendicular-distance.js:1
API and Integration
The module is exported as an ES module, allowing for modern integration in JavaScript environments.
| Parameter | Type | Description |
|---|---|---|
points | Array<Object> | An array of objects with lat and lng properties. |
epsilon | Number | The maximum distance (in degrees) for simplification. |
Sources: README.md:32-38, package.json:10
Conclusion
The geo-path-reducer architecture provides a lightweight and efficient implementation of the Douglas-Peucker algorithm. By decoupling the recursive logic from the geospatial mathematics (Great-Circle and Heron's formula), the library remains maintainable and focused on its core task of path simplification.