Today’s Question: I’m planning to use a track log program on my smartphone to create track logs for geo-tagging my photos. The program’s default location sampling interval is 1 second. It seems to me that would create excessive location data over a trip that might last a week or more. What would you recommend for a location sampling interval for the purposes of Geo tagging my photos?
Tim’s Quick Answer: As a general rule I recommend recording track logs with an interval of about 15 seconds. However, it is important to consider how fast you might be moving and the degree of precision you’d like to have for your location metadata.
More Detail: A GPS track log records the current time and your current location at a set interval. Your camera includes the date and time of capture in the metadata for each photo. Since the track log and your photos both contain time information, you can synchronize your photos with a track log based on time. In other words, by recording a track log during the time that you are also capturing photos, you add GPS coordinates to the metadata for those photos later in your workflow.
Of course, chances are there won’t be a track log location data point that correlates with the precise time a given photo was captured. Instead, the track log data needs to be interpolated in order to estimate the specific location for each photo. The frequency of recording location data points for the track log determines how significantly the data needs to be interpolated. That, in turn, affects the accuracy of the location information added to each photo based on the track log.
So, in concept you want to record a track log with a very short interval. That would certainly result in a larger track log file than you would get with a longer interval setting, but the data is very simple and thus won’t result in an extremely large file size even with a track log recorded over the course of multiple days.
The bigger concern is generally battery life. The more frequently you are recording data points for a track log, the more your device will be tracking GPS satellite signals and processing that data. Using a lower track log frequency will help preserve battery life.
The right balance will vary for each photographer, depending on how much (and how fast) they move around during photography, and how critical it is to have very precise location information. For most photographers I find that an interval of fifteen seconds works well, but you may want to use a shorter interval if you’re moving quickly and want precise location data. You might also prefer a longer interval if you only need to know the general location (rather than very precise location) or don’t tend to move across large distances during your photography.