GPS File Formats for Photo Geotagging

GPS Track Logs: The Foundation of Photo Geotagging

To geotag photos based on where they were taken, you need a GPS track log — a record of your journey with timestamps and coordinates. HoudahGeo matches your photos to these GPS tracks by synchronizing timestamps, automatically assigning precise locations to every image.

The quality and compatibility of your GPS track logs directly affects how accurately your photos can be geotagged. Understanding GPS file formats helps you choose the right devices and ensure long-term access to your location data.

Industry Standard GPS File Formats

Two primary file formats dominate GPS track logging: GPX and NMEA. Both are open standards with widespread support across devices and software.

Why GPX is the Best Choice

HoudahGeo's preferred format is GPX because it provides the most reliable and future-proof way to store GPS track data:

• Open Standard: GPX is an open, well-documented XML format that any software can read and write
• Complete Information: Stores all necessary data including precise timestamps, coordinates, and altitude
• Human-Readable: XML structure means you can view and verify track data in any text editor
• Universal Compatibility: Supported by virtually all GPS software, mapping tools, and geotagging applications
• Long-Term Accessibility: Your GPX files will remain usable decades from now, regardless of device manufacturer support

Other GPS File Formats

Many GPS devices and applications use proprietary or specialized file formats. HoudahGeo can read many of these by internally relying on GPSBabel — a free, open-source tool that converts between dozens of GPS file formats.

Supported formats through GPSBabel include:

• Garmin FIT files (.fit)
• Garmin TCX files (.tcx)
• Google Earth KML/KMZ (with limitations — see below)
• Magellan track files
• TomTom track logs
• IGC flight recorder format
• Lowrance USR files
• OziExplorer files
• Dozens of other manufacturer-specific formats

When you import a track log file in HoudahGeo, the software automatically detects the format and converts it internally if necessary, making the process seamless.

Important: KML Format Limitations

Google Earth's KML (Keyhole Markup Language) format is widely used for visualizing geographic data, but it has a critical limitation for photo geotagging:

The Timestamp Problem

HoudahGeo relies on exact time information to match photo timestamps to points on a recorded GPS track. Without precise timestamps at each track point, it's impossible to determine where you were when each photo was taken.

The KML specification doesn't define a standard way to include timestamps with track points. Different vendors use different approaches:

• Some embed date and time in free-form text comments
• Others use custom XML extensions
• Many KML files contain no time information at all
• Even when timestamps exist, there's no guarantee HoudahGeo can parse the vendor-specific format

Recommendation: If your GPS device or application exports to KML, check whether it also offers GPX or NMEA export options. Always prefer GPX for photo geotagging workflows.

Choosing a GPS Device for Photography

For photo geotagging, the best GPS device is one that logs tracks and can export them in standard formats like GPX or NMEA. Here's what to look for:

Alternative GPS Sources

You don't necessarily need a dedicated GPS logger. Many other devices can provide GPS track logs:

• Smartphone Apps: Apps like Trails, GPX Tracker, or MotionX GPS can record tracks and export GPX files
• Sports Watches: Garmin, Apple Watch, Suunto, and other GPS watches log activities and can export track data
• Fitness Apps: Strava, RunKeeper, and similar apps record routes that can be exported as GPX files
• Cycling Computers: Garmin Edge and similar devices create detailed GPS logs
• Drone Flight Logs: Many drones record flight paths with GPS coordinates and timestamps
• Vehicle GPS Systems: Some car GPS units and dash cams log routes

Working with Manufacturer Software

If your GPS device doesn't have direct connectivity or uses a proprietary format, you have options:

• Manufacturer Software: Most GPS manufacturers provide desktop applications to download and export track logs — look for GPX export options
• GPSBabel: This free, open-source application can convert between dozens of GPS file formats, including many proprietary formats
• Web Services: Some manufacturers offer web portals where you can access your tracks and download them as GPX files

Testing Device Compatibility

Before committing to a GPS device for your photography workflow, verify compatibility with HoudahGeo:

1. Record a test track: Take your GPS device on a short walk or drive while taking a few photos
2. Export the track: Use the device's preferred method to get the GPS log onto your Mac
3. Download HoudahGeo's free trial: Import the track and your test photos to verify the workflow
4. Check timestamp accuracy: Ensure photos match to the correct locations along your route

Best Practices for GPS Track Logging

Optimize Logging Settings

• Logging Interval: Set your GPS to record points every 5-10 seconds for detailed tracks, or every 30-60 seconds for battery conservation
• Auto-Start: Enable automatic track logging when movement is detected so you never forget to start recording
• File Naming: If your device supports it, use automatic date-based file names for easy organization

Synchronize Camera and GPS Time

Accurate geotagging depends on synchronized clocks:

• Set your camera's clock to match GPS time (which is always accurate)
• Account for timezone differences if your camera uses local time
• Check and adjust camera time when traveling across time zones
• HoudahGeo can compensate for time offsets, but prevention is better

Archive and Organize GPS Tracks

• Convert to GPX: If your device uses a proprietary format, convert tracks to GPX for long-term storage
• Organize by Date: Store GPS tracks alongside corresponding photos using a consistent folder structure
• Backup Regularly: GPS tracks are irreplaceable — include them in your backup strategy
• Keep Original Files: Maintain both proprietary and GPX versions if converting from another format

The Future-Proof Choice

GPS devices come and go. Manufacturers discontinue products, abandon software support, and change file formats. By choosing devices that support GPX export and archiving your tracks in GPX format, you ensure your location data remains accessible regardless of future technology changes.