Do your photos have EXIF time stamps?
A photo must have a valid EXIF time stamp in order to georeference it from a GPX track log. If it has one, it will display in the main image list. Remedy: Either manually enter a timestamp or geocode manually using Google Maps or Google Earth.
Was the camera clock set correctly?
HoudahGeo relies on the camera clock working consistently over the course of a project. If your camera clock was consistently off by a certain number of seconds, you may input this clock error when importing the first image into the project.
Remedy: If the clock error has changed over the course of the project you will need to manually edit the timestamps.
Was the time zone configured correctly?
HoudahGeo inquires about the camera time zone when importing the first image into the project. You need to provide accurate information. Typically this is either your home time zone or the time zone you travelled to.
Remedy: Start a new project and enter the correct information.
Do the photo times fall within the time frame of the track log?
In order to geocode a photo, its timestamp must fall between the time of two consecutive track points in a given track log segment. Photos taken outside the time span covered by the track log can thus not be geocoded. If you expect the photo to fall within the correct time frame, you may want to double check the camera time zone and clock error settings.
Remedy: Either manually enter coordinates or geocode manually using Google Maps or Google Earth.