Here's an update to my review of GPS4cam, the geotagging app that runs on your SmartPhone.
In order to geotag your images, the desktop software must be able to locate the images and the barcode. This means you must either download them to some temporary location or process them on the camera media itself.
For me, at least, the second option is too slow to be effective. I get much more rapid results when the images are on the hard drive of my computer.
The images should not be in a subdirectory (folder) that contains a number of other images. That will really slow things down. I download mine to a folder called gps4cam_temp, process the images there, then import them into Lightroom using the "Move" option, so that the temporary folder is cleaned out and ready for the next batch.
In cases where your trip has taken some time (two days or more), the export option on your smartphone is likely to produce more than one bar code. You must photograph all of them. Therefore, after running the export command and photographing your bar code, swipe your finger across the screen to make certain there's not another one there.
Again, this little app is quite accurate and remarkable both for its low cost and cord-free approach.
And to reemphasize a point I made in the original review, the fact that you may not currently own software that displays the geotag information does not mean that you shouldn't use this tool. I predict that all software will eventually support it, as well as all popular web-sharing sites. (Flickr, for instances, already does.) Therefore I advise that you start geotagging photos taken at geographically significant locations -- in other words, anything except portraits, family gatherings, weddings, etc. -- now so that you will have access to this information in years to come.