I already wrote a few articles about how to use my preferred GPS logging device, the Holux M-241, on the Mac. In this article I’m focusing on the linking process between the GPS data and the photos. This process is called a geotagging workflow. Most of the time I’m taking pictures in RAW mode so the workflow is optimized for this type of images. I’m using a Nikon D80 but the workflow should work with almost any other (Nikon) digital camera like the Nikon D200 or Nikon D300 too.
Equipment/Tools needed for the Nikon D80
- GPS logging device, e.g. the Holux M-241
- Software to extract GPS data from the GPS logging device. See here if you’re using a Holux M-241 GPS logger on the Mac.
- Aperture 2
- Ovolab GeoPhoto is one of the few tools available on the Mac which is able to process RAW photos from an Aperture project.
It may all work well with other tools though. Just drop a comment if you’re successfully using a different toolset/workflow to geotag Nikon RAW images on the Mac.
Things to do before you start shooting
These steps may seem a bit tedious but they’re going to save you a lot of time later on.
- Switch the GPS logging device on, wait until it has a satellite fix and turn logging on. Most loggers start logging automatically once they’re switched on.
- Make sure the GPS logger is set to the correct time zone. Its clock will automatically synchronize to the GPS clock from the satellites.
- Synchronize the clock in the Nikon D80 to the clock in your GPS logging device. Go to the wrench symbol in the menu and select “World time”. The date/time displayed at the bottom should be the same as in the GPS logger. The more the clocks are in sync, the more precise the match later on.
- This one is very important: make sure you put the GPS logging device in a place where it has free line of sight on the sky at all times. The more GPS satellites it can “see” at any given moment, the more precise the position data will be. Your GPS logger even may have an indicator which side should point upwards.
Please note: you don’t have press a waypoint button or anything else on your GPS logger once you take a picture. The GPS logger constantly logs your current location and depending on the logging interval there’s a good chance for a pretty close match. Usually, I use a 5 second interval on my GPS logger. Of course you can select a shorter interval if your GPS logger supports this but battery life will be shortened too. I found 5 seconds a pretty good compromise.
Geotagging workflow using Aperture 2 & GeoPhoto
I’m assuming that you already downloaded the GPS data from your GPS logger and converted it to a format that Ovolab’s GeoPhoto is able to import. If you’re using a Holux M-241, see here for instructions.
- Download the RAW images from your camera/memory card into an Aperture project of your choice. In the import dialog, make sure you don’t adjust the time settings.
- Open GeoPhoto, select “File” -> “New”
- Click the “Media” icon and select your Aperture project
- Use Command-A to select all pictures in that project and drag all the files to your GeoPhoto library. They all will be shown in the preview strip with a small, striked-through globe which indicates they don’t contain any geolocation – yet.
- Use Command-A in the preview strip to mark all photos.
- In the “Item” menu, select “Match Items to GPS track…”
- Choose the GPS log file or download it directly from one of the supported devices. If you’re using a Holux M-241, select the previously exported .kml file.
- If you didn’t forget to synchronize the GPS logger with your camera, all photos will be automatically assigned a location.
- Hit apply. Now the GeoPhoto library “knows” where you took your pictures but we want to have that information in our RAW .NEF files too.
- That’s why you select all pictures using Command-A in the preview strip, right-click and select “Update (number of) originals with location information”. All your .NEF files will now be updated with geolocation data.
- There is certainly a lot more to see in GeoPhoto (e.g. the Flickr integration) but for now we’re done with it. Hit Command-Q to close it.
- Let’s go back to Aperture to see if there is any geolocation information in our pictures. Switch to the metadata tab and select a picture.
- Select the “General” metadata view. At the bottom there will be three EXIF metadata fields: latitude, longitude and altitude. But they’re empty?! Yes, that’s because Aperture doesn’t know we externally modified the master .NEF file.
- In the Aperture preview strip, right click an image an select “Update EXIF from master”.
- Tadaa… there’s the geolocation data. Of course you don’t have to do this for every single image. Select them all using Command-A in your preview strip and select “Update EXIF from masters”.
- Once a picture is geotagged you can right-click it, select “Show on Map…” and Google Maps will show you the location in the web browser.
That’s it! If you have an idea about how to further optimize this workflow please drop a comment, thanks!
But wait, there’s more: altitude correction. Some GPS loggers aren’t very good in determining the precise altitude. Using GeoPhoto you can correct altitude data based on the 2D longitude/latitude coordinates. Command-A select all your photos in the preview strip and click the blue inspector icon on the menu bar. In the inspector menu, select “Look up Altitude at this Location” and all your selected photos will be updated with precise altitude data taken from Google Maps. Ain’t that cool?
Don’t forget to update your originals every time you modify EXIF data in GeoPhoto and to update the master EXIF data in Aperture.