How to Convert GNSS Coordinates from WGS84 to UTM and Local Grid
Most GNSS receivers output coordinates in WGS84 (latitude and longitude). But for mapping, CAD, or official land registration, you often need data in UTM (Universal Transverse Mercator) or a local grid projection.
This guide will walk you through the tools and steps to convert your GNSS data accurately — so you can avoid mismatched data, scale errors, or position shifts in your maps.
📍 Step 1: Understand the Coordinate Systems
- WGS84: Global coordinate system used by GNSS — based on latitude & longitude.
- UTM: Zone-based metric system — used for large-scale mapping.
- Local Grid: Custom projection (e.g., country-specific, site-local) often used in government and engineering projects.
💡 Your country or region likely has a local official grid (e.g., ID74 for Indonesia, NAD83 for US, ETRS89 for Europe).
🧪 Step 2: Collect GNSS Data in WGS84
- Use your GNSS receiver to log position data (Rover survey)
- Ensure the output includes Latitude, Longitude, and Ellipsoidal Height
- Preferably export in CSV, TXT, or RINEX format
✅ Many apps like FieldGenius, SurvCE, or Emlid Flow let you export coordinates directly.
🛠️ Step 3: Convert Using These Tools
1. Online Tools
- EarthPoint – WGS84 to UTM (Google Sheets/Excel)
- EPSG.io – Transform between EPSG codes
2. Software
- 📐 QGIS: Open-source GIS software with full coordinate transformation tools
- 🧮 AutoCAD Civil 3D: Use coordinate system manager to reproject points
- 📊 Excel: With formulas or VBA to convert using UTM zone formulas
3. GNSS Software
- 🛰️ Leica Infinity, Trimble Business Center, Emlid Studio
- ✅ Import base + rover log, and export with transformed coordinates
📏 Step 4: Determine Your UTM Zone
UTM zones are 6° wide longitudinal strips. Use your Longitude to identify your zone:
- 📍 Longitude 96°E to 102°E = UTM Zone 48N
- 📍 Longitude 102°E to 108°E = UTM Zone 49N
🧭 Make sure to select the correct **North or South Hemisphere** option when converting!
🧰 Step 5: Local Grid Transformation (Optional)
To transform to a local or site-specific coordinate system, you may need:
- 📍 Local datum and projection parameters (e.g., Transverse Mercator, Lambert)
- 📄 A grid shift file or 7-parameter transformation file
- ⚙️ Software like QGIS, Surfer, or Leica Infinity
🔑 Many countries provide downloadable coordinate transformation files via their survey departments.
💡 Pro Tips for Accuracy
- ✔️ Use a fixed solution (RTK or PPK) for collecting WGS84 coordinates
- ✔️ Double-check UTM zone and hemisphere settings
- ✔️ When converting for government or engineering use, verify the local grid spec (EPSG code)
🎯 Final Output
After conversion, you can export your data as:
- CSV or Excel (for CAD import)
- DXF with UTM coordinates (for design overlays)
- GeoJSON or SHP files (for GIS mapping)
🙋 Need Help With Coordinate Conversion?
We assist in coordinate conversion, grid matching, and export to CAD-ready formats. Contact us with your WGS84 data file and target projection.
Next article: “How to Process Static GNSS Data for Post-Processing (PPK)”