Hi CL folks:
As promised, here is the tutorial for geo-tagging pictures with an external GPS unit. This is the very first tutorial I ever write, so please take it easy. Enjoy.
I quickly found out that geotagging is a fascinanting feature of digital photography. Why? For an amateur photographer like myself, the fact that you can place your pictures on maps with great precision, trace your journey on a certain foreign landscape with a combination of blog text, pictures and GPS coordinates offers the reader (and yourself later for your own memories) a complete experience of the journeys you have done. I now have thousands of geotagged photos on my photo library and seeing those trips through maps/images is always fascinating to me.
In this tutorial, I will show you how to geotag images by using an external GPS unit. There are lots and lots of software you can use for this purpose, so writing a guide to each one individually is out of the question. However, most GPS editors incorporate the features I will describe here, so I don’t think you’ll have a problem.
How to choose a GPS unit
I use a Garmin Oregon 300 GPS unit. I hike a lot on the Swiss alps, so an external GPS unit is very useful for me for land navigation. You do not need a sophisticated GPS unit, though. You need only a GPS device that can track your path and be able to export it on .gpx format.
You can use a GPS-enabled cellphone if you want to, but cellphones have a problem: battery life. If I set my iphone (with a third-party) application to track my path, the battery will be gone in about 3 hours. This is of course a thing to consider if you are going to do long trips. Now, let’s get to the hands-on part!
I. Preparing to geotag
When you go outside to enjoy the wonders of nature, take you photo camera with you and your GPS unit. The first thing you will do once you reach the start of your journey, is to turn on the GPS unit. Wait for it to acquire a satellite signal with acceptable accuracy. Something between 30-7 meters is OK, though this really depends on the accuracy of your own GPS unit and the current conditions. Once you have locked-on a GPS signal, take your camera and take a picture of your GPS. The GPS screen should be displaying the coordinates. That’s it, put the GPS back on your pocket, and start your journey and take as many pictures as you want. Easy, right?
II. Post production
The last thing you want to do is to geotag your pictures. So once you get back to your computer, load the photos, do some post-processing, watermark them, execute your workflow as you always do, and once you are done, follow these steps to geotag your images.
The software I use is called PhotoGPSEditor (http://www.mmisoftware.co.uk/pages/photogpseditor.html
). It is a free GPS tool for Mac. This particular software is not available for PC, but there are other free geotagging apps out there, just Google it.
Your GPS captures your trip by recording GPS coordinates every certain period of time. For example, my Garmin Oregon 300 records the current latitude, longitude and altitude every 30 seconds. Each GPS record is accompanied by a timestamp. The trick is matching these timestamps with the timestamps of your digital images. We could do that manually, but if you went out in the wilderness and took 800 images, the task can be daunting, right? Software like Photo GPS Editor allows us to automate this timestamp matching with great precision. It just needs one hint from us to do it. Remember that first picture you took of your GPS unit at the beginning of the trip? This is the point at which that photo becomes useful. By having a picture with the exact GPS coordinates (the beginning image of your photo-shoot, let’s say), the application can calculate the offset (difference) between your camera’s time and the GPS’s time and apply that difference to all the images you took. Ready to try it out?
Once you open the program, the first screen will present you with the option to begin the process, or enter the advanced mode. Click on “Start“.
On step 2, you need to load your photos to the program. Click on the button “Load Photos“ and search for the corresponding files. Remember that you should do the geotagging process after doing post-processing. Once you select the files, the filenames should appear on the left-hand side frame. Click on the “Next“ button.
Here, you have to load the .gpx file the comes out of your GPS unit. In case of my GPS unit, I just plug it to my computer with a USB cable and it is recognized as an external storage drive. Depending on your particular GPS unit, you might need proprietary software to export the recorded path to a gpx file. Click on the “Load GPS file“ button and search for your .gpx file. Once you select it, you will see a bunch of track points listed on the screen. Click on the “Next“ button.
On the next screen, click on the “Offset by lat/lon“ button. PhotoGPSEditor offers three ways to offset the time differences between your GPS unit’s recorded time and your camera’s, but the most exact one of to do it by lat/lon.
Now, here comes the magic. On the “Pictures“ pane on the left-hand side of the screen, look for the picture you took of you GPS unit at the beginning of the trip. Now, open up that file with you favorite picture viewer. Note the listed GPS coordinated. Back on the PhotoGPSEdit, write these coordinates on the “Known lat/lon for picture“ text fields. Remember to click the “Deg/Min“ button. Once you gave in the coordinates, click the “Offset“ button. Click the “Next button“.
Click the “Apply to all photos“ now. This will propagate the offset of time/coordinates to the rest of the pictures you selected on step 2. Click “Next“ button.
Here you can add some descriptions, comments for the pictures. Click the “Next“ button.
Click the “Save Photos“ button. PhotoGPSEditor will ask you for a folder to save the pictures with the geotags. The software will NOT overwrite your existing files, it will instead create copies of your pictures with the added GPS information. So select a folder to save these geo-tagged copies and wait until the program finishes copying the modified files. Once this is done, quit the application.
As you can see on the next picture, the photo is properly geotagged (even with altitude information!).
Though there are other ways to geotag pictures (like taking a corresponding picture with your iphone), this is the best way I have found to geotag lots and lots of pictures, with only the minimum effort of taking a picture of your GPS at the beginning of your trip.
So now, get out there onto the wilderness, start taking pictures, and enjoy the great feature of having precise GPS coordinated added to them!