Coordinate Reference Systems (CRS)

Overview

Maptaskr uses a standardized approach to coordinate reference systems to ensure consistency and compatibility across all mapping operations. This document explains how coordinate systems work within Maptaskr and what you need to know when working with spatial data.

Key Coordinate Systems

EPSG:4326 (WGS84)

• Primary system: All data input and output uses WGS84
• Format: Latitude/Longitude in decimal degrees
• Range: Latitude: -90° to +90°, Longitude: -180° to +180°
• Usage: Standard for GPS data, GeoJSON, and most web mapping applications

EPSG:3857 (Web Mercator)

• Rendering system: Used internally by MapLibre for display
• Also known as: "Google Mercator" or "Spherical Mercator"
• Usage: Optimized for web map rendering and tile display

How Maptaskr Handles Coordinates

Data Input and Storage

All spatial data in Maptaskr follows these standards:

1. Tile Server Requests: Data is requested in EPSG:4326 (WGS84)
2. External Server Requests:
   • Without Client-Side Reprojection: Requests made in EPSG:4326
   • With Client-Side Reprojection: Requests made in the server's native format, then reprojected to EPSG:4326
3. Geodata Creation: All drawn features are saved in EPSG:4326, following GeoJSON specification

Rendering Process

The coordinate transformation follows this workflow:

Input Data (EPSG:4326) → MapLibre Processing (EPSG:3857) → Screen Display (x,y pixels)

1. Input: Data provided in WGS84 (EPSG:4326)
2. Processing: MapLibre reprojects to Web Mercator (EPSG:3857) for rendering
3. Display: Final projection to screen coordinates based on map view (globe or planar)

Client-Side Reprojection

What is Client-Side Reprojection?

Client-side reprojection allows Maptaskr to work with external map servers that use different coordinate systems by:

• Requesting data in the server's native coordinate system
• Automatically converting it to WGS84 for consistent internal handling
• Providing better performance and accuracy for certain data sources

When to Enable

• Enable when working with servers that have optimized native projections
• Disable for standard WGS84 sources to reduce processing overhead

Best Practices

For Users

• Always provide data in WGS84 (EPSG:4326) when possible
• Use decimal degrees format (e.g., 40.7128, -74.0060 for New York City)
• Ensure your GPS devices and data sources output WGS84 coordinates

For Developers

• Assume all API inputs and outputs use EPSG:4326
• When integrating external data sources, verify their coordinate system
• Use the client-side reprojection feature for non-WGS84 sources

Support for GDA2020 (or any other CRS) via ArcGIS Enterprise (or Online)

Maptaskr Power Maps is a web-based mapping application that renders map content using Web Mercator (EPSG:3857) and WGS84 (EPSG:4326) for performance and browser compatibility. Support for GDA2020 is achieved through integration with Esri ArcGIS, which serves as the authoritative spatial system of record.

Authoritative storage in GDA2020

• Spatial data is stored and managed within Esri ArcGIS in its authoritative coordinate reference system, including GDA2020 (e.g., EPSG:7844).
• ArcGIS is responsible for enforcing spatial reference integrity, datum definitions, and configured transformation rules.

On-the-fly transformation managed by ArcGIS

• Maptaskr requests spatial services from ArcGIS in WGS84 (EPSG:4326) for features, and Web Mercator (EPSG:3857) for images.
• Local transformations are applied to the returned GeoJSON features to convert them to Web Mercator (EPSG:3857) for rendering on the map.
• ArcGIS performs standards-based on-the-fly transformations from GDA2020 to WGS84 or Web Mercator using its geodetic transformation engine and configured transformation pipelines. This ensures accurate visualization while maintaining the dataset’s authoritative CRS.

Capture, editing, and round-tripping accuracy

• When users create or edit geometries in Maptaskr, those geometries are:
  • Captured as GeoJSON in WGS84 (EPSG:4326), consistent with the GeoJSON specification (RFC 7946 - The GeoJSON Format),
  • and Submitted back to ArcGIS via Esri connectors, where the server applies the appropriate reverse transformation and persists the geometry in the authoritative CRS (e.g., GDA2020).
• This round-trip approach ensures that the ArcGIS systems are utilised for alignment with authoritative datasets, and datum handling across the full edit lifecycle.

Clear separation of responsibilities

• Maptaskr: user experience, workflow, business logic, and web map interaction.
• Esri ArcGIS: spatial storage, CRS management, datum transformation, and geodetic accuracy.

This separation aligns with best practice for enterprise spatial architectures and avoids duplication of spatial transformation logic within application layers.

Additional Resources

• MapLibre Coordinate System Documentation

Quick Reference

Operation	Input CRS	Output CRS	Notes
Data Import	EPSG:4326	EPSG:4326	No conversion needed
Map Display	EPSG:4326	EPSG:3857	Automatic reprojection
Data Export	EPSG:4326	EPSG:4326	Consistent with input
API Responses	EPSG:4326	EPSG:4326	Always WGS84

Summary

Keep it simple: Provide all data in WGS84 (EPSG:4326) format, and Maptaskr will handle all necessary coordinate transformations automatically.