In a field with a lot of technical terms and concepts, such as aviation, some terms are likely to be confusing. Let’s look at the concepts of Threshold elevation (THRE) and Touchdown zone elevation (TDZE).
What is Touchdown zone?
The portion of a runway, beyond the threshold, where it is intended landing aeroplanes first contact the runway. – Source: ICAO Annex 14
What is threshold?
The runway threshold is the position across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.
What is Displaced Threshold?
A threshold not located at the extremity of a runway. – ICAO Annex 14
What is Runway?
Defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft. – ICAO doc4444
The TDZE is defined as the highest elevation in the first 3000 feet of the runway starting at the threshold.
So, if Threshold consists the highest point in Touchdown zone area, TDZE = THRE.