Advanced users may opt to generate KML files from a HoudahGeo project. KML is an open standard. It is supported natively by Google Earth and Google Maps. Unlike KMZ, it is not self-contained. The KML file references image files residing next to it. This makes managing KML files pretty tricky.
We can distinguish two types of KML files:
- The first is used locally on a computer. This one is easiest to create and to share. One only needs to take care to move the images along with the KML file and keep their relative position the same.
- The second type of KML is needed for files stored on a web server. As the reader must know where on the server to find the matching image files, the base URL for image files needs to be stored within the KML file. Thus one needs to know that URL at the time the KML is created. The KML can then be tested only once both the KML and the appropriate image files have been uploaded to said server.
For most uses a Google Earth KMZ file is the better choice. Basically KML files should only be used by those running their own web server.
Selected images only
Only images previously selected in the main window will be exported.
Root caption
This is the title by which your project will be known in Google Earth. Your project will be listed with this name under "My Places" within Google Earth
Altitude mode
This defaults to "Clamped to ground". Google Earth will assume that all photos were taken at ground level. The use of the "Actual altitude" mode makes sense only if your images have been geocoded with altitude information. There is a risk of images not showing in Google Earth if they are tagged with an altitude below ground level.
Use thumbnail images
By default the KMZ will be configured for Google Earth to display markers at the positions where photos are located. You may choose to display thumbnail images rather than standard markers.
Large image size
When a marker is clicked, Google Earth will display a preview of the corresponding photo. You may choose between 3 sizes for these preview images. If file size is an issue, you should prefer the smaller size.
Include track log
You may include relevant parts of a loaded GPS track log. This shows how you got from one photo location to another. The display of the track log within Google Earth is optional. When enabled it shows as a red line.
Base URL
HoudahGeo will generate a folder structure containing the actual KML file as well as the thumbnails and images it references. Base URL specifies where the KML file will ultimately be stored.
- If no "Output base URL" is specified, the KML file will work only locally. If you want to pass it on to someone else, you need to copy the folder structure as is.
- If base URL is specified, the KML expects the output folder to be placed at the specified location on a web server. Until you do so, the KML file cannot access or show photos. Once the photos are publicly available, you may pass along or make available for download the KML file. You may also use Google Maps to view the KML file.