Development Setup
Relevant source files
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This page provides technical documentation for the development environment and implementation details of the geo-path-reducer library. This project implements the Douglas-Peucker algorithm to simplify curves represented by geographical coordinates (lat/lng), facilitating reduced complexity in spatial data processing.
The module is built using modern JavaScript (ES Modules) and is designed to be integrated into Node.js or browser-based projects via npm. Sources: README.md:1-5, package.json:10
Project Configuration
The project is structured as a lightweight Node.js module. It uses package.json to define metadata and entry points.
Package Metadata
| Property | Value | Description |
|---|---|---|
name | geo-path-reducer | Unique identifier for the npm registry. |
version | 1.0.0 | Current semantic version. |
type | module | Specifies the use of ES Modules (ESM). |
main | src/index.js | Primary entry point for the library. |
license | MIT | Legal usage permissions. |
Sources: package.json:2-11
Scripts and Commands
The project defines basic lifecycle scripts for development:
test: Currently a placeholder that outputs an error message, as no tests are specified in the current version.
Sources: package.json:6-8
Module Integration
The library can be installed and imported into any JavaScript project. The installation utilizes the standard npm registry.
npm install geo-path-reducer
Sources: README.md:9-11
Usage Pattern
Developers import the primary reducer function to simplify arrays of geographical points based on a specific tolerance (epsilon).
import geoPathReducer from 'geo-path-reducer';
const points = [{ lat: 37.7749, lng: -122.4194 }, ...];
const epsilon = 0.0001;
const simplified = geoPathReducer(points, epsilon);
Sources: README.md:17-31
Algorithm Implementation
The system is composed of three core mathematical modules that work together to simplify paths.
Dependency Flow
The following diagram illustrates how the modules interact to perform the path reduction:
The entry point relies on perpendicular distance calculations, which in turn require spherical geometry calculations to determine distances between coordinates on Earth. Sources: src/index.js:1, src/perpendicular-distance.js:1
Core Components
1. Path Reducer (src/index.js)
This is the implementation of the Douglas-Peucker algorithm. It finds the point with the maximum perpendicular distance from the line segment formed by the start and end points. If this distance exceeds epsilon, it splits the path at that point and recursively processes both halves.
Sources: src/index.js:3-26
2. Perpendicular Distance (src/perpendicular-distance.js)
Calculates the distance from a point to a line segment using Heron's formula for the area of a triangle.
- Formula logic: Given distances
d1,d2(point to segment ends), andd3(segment length), it calculates the semi-perimeters, then the triangle area, and finally the altitude (distance).
Sources: src/perpendicular-distance.js:3-11
3. Distance Calculation (src/distance.js)
Implements the Haversine formula to calculate the great-circle distance between two points on the Earth's surface in kilometers.
- Earth Radius (R): 6371 km.
- Coordinate Conversion: Degrees are converted to radians using
Math.PI / 180.
Sources: src/distance.js:3-16
API Specification
The primary API is a single function exported as default.
geoPathReducer(points, epsilon)
| Parameter | Type | Description |
|---|---|---|
points | Array<Object> | Array of objects containing lat and lng properties. |
epsilon | Number | Maximum allowed distance (in degrees) between the original and simplified curve. |
Returns: A new Array<Object> containing the simplified sequence of points.
Sources: README.md:35-42, src/index.js:3
Summary
The geo-path-reducer development setup is optimized for simplicity and modularity. By leveraging ES Modules and isolating mathematical logic (distance and perpendicular distance) from the recursive algorithm (Douglas-Peucker), the project maintains a clear separation of concerns. Developers contributing to the project should focus on maintaining the mathematical accuracy of the Haversine and Heron's formula implementations within the src/ directory. Sources: src/index.js, src/distance.js, src/perpendicular-distance.js