Some iPhone/iPad photos do not appear on the map of iPhoto It happens to me sometimes that using iPhone or iPad, I take pictures in open air environments, but later, when photos are exported to iPhoto, they do not appear on the Map. What could be the cause?
You can add or correct wrong GPS-data to your photo with the app iMetaPhoto.

I had the same problem, I took 4 photos at the same location, but only the last photo was correctly geotagged. Wit iMetaPhoto you can take this correct GPS-data and save it to the wrong ones.