Coordinate Systems (CRS)
The Cityweft API supports three different coordinate reference systems to accommodate various use cases and integration requirements. Choose the appropriate CRS based on your use case
local Local Coordinate System
Relative to origin point
Small sites, game engines, visualization
Meters from origin
Universal Transverse Mercator
GIS, surveying, precise mapping
UTM zone coordinates
Local Coordinate System
Parameter: crs: "local" (default)
Description
The local coordinate system positions all geometry relative to a specified origin point. This creates a localized coordinate space with the origin at (0,0,0).
Characteristics
Origin: User-defined point or first polygon vertex
Units: Meters
Coordinate Space: X-right, Y-forward/back, Z-up (depending on upAxis parameter)
Range: Suitable for sites up to ~10km radius
When to Use
✅ Game engines (Unity, Unreal)
✅ 3D visualization applications
✅ Small to medium-sized sites
✅ When you need simple, relative coordinates
❌ Large geographical areas (>10km)
❌ When integrating with GIS systems
Output format:
{
"spatialReference": {
"crs": "local",
"origin": [52.5200, 13.4050]
},
"geometry": [...] // Coordinates relative to origin
}Web Mercator (EPSG:3857)
Parameter: crs: "EPSG:3857"
Description
Web Mercator is the standard projection used by most web mapping services (Google Maps, OpenStreetMap, Mapbox). Coordinates are in the global Web Mercator coordinate system.
Characteristics
Origin: Global (0,0) at the intersection of the equator and the prime meridian
Units: Meters (keep in mind the Mercator distortion)
Projection: Spherical Mercator
When to Use
✅ Web mapping applications
✅ Integration with web map services
✅ Global or continental-scale projects
✅ When working with existing Web Mercator data
❌ High-precision surveying
❌ Polar regions (>85° latitude)
Output format:
{
"spatialReference": {
"crs": "EPSG:3857"
},
"geometry": [...] // Global Web Mercator coordinates
}Universal Transverse Mercator (UTM)
Parameter: crs:"UTM"
Description
UTM divides the world into 60 zones, each 6° wide (with some exceptions like Norway mainland and Svalbard). The system automatically detects the appropriate UTM zone based on your polygon's location and provides high-precision coordinates.
Characteristics
Origin: Zone-specific (500,000m Easting, 0m or 10,000,000m Northing)
Units: Meters
Projection: Transverse Mercator per zone
Accuracy: Sub-meter precision within zone
Auto-detection: Zone calculated from the polygon center
When to Use
✅ GIS applications (QGIS, ArcGIS)
✅ Surveying and engineering
✅ High-precision mapping
✅ CAD integration
✅ Construction and infrastructure projects
❌ Cross-zone projects (spanning >6° longitude)
❌ Simple visualization needs
Output format
{
"spatialReference": {
"crs": "UTM",
"utmZoneEPSG": "EPSG:32633",
"zoneString": "33N",
"hemisphere": "N",
"zone": 33,
"letter": "N"
},
"geometry": [...] // UTM zone coordinates
}Integration Compatibility
Game Engines
local
Web Maps
EPSG:3857
GIS Software
UTM
CAD Software
UTM or local
3D Modeling
local
Error Handling
Invalid CRS values default to 'local'
UTM zones are auto-calculated; manual specification is not required
Cross-zone polygons use the zone of the polygon centroid
Performance Notes
Local & EPSG:3857: Fastest processing, minimal coordinate transformations
UTM: Slightly slower, requires zone calculation and transformation
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