Lear about Glide Path here:
http://www.pilotfriend.com/training/flight_training/nav/ils.htm
“Brief description
The ILS usually consists of a Localizer, Glide Path, and Markers(OM, MM, & IM).
Localizer: This equipment provides lateral guidance to the runway centreline from about 5nm out.(five nautical miles).
Glide Path: This equipment provides the aircraft with a glide angle - usually 3 degrees. The Localizer and Glide Path combine to bring the aircraft to a point where the aircraft is 50 feet high at the runway threshold (decision point).
Markers:
1. The Outer Marker at approximately 5nm helps the a/c adjust its course and height.
2. The Middle Marker is located at approximately 3500 feet uand used similarly.
3. The Inner Maker at 1000 feet is used only for Category II operations.
Exceptions:
There are always exceptions and here are some main exceptions.
1. DME & GP (Distance Measuring Equipment & Glide Path) when it is impossible to have Markers.
2. DME & Localizer when there is no GP for whatever reason.
3. Offset Localizer. In this case the Localizer is not on the runway centreline, but offset and lined up to bring the aircraft over the threshold at decision height. Decision height is 50 feet at threshold.”
And by the way, it is 28L and not 29L.