Vegetation 1

26.03.2010

Submission:

Firstly I would like to express my gratitude for all of you who contributed to the clarification of the buffer area appliance in TMA's. All relevant information and details provided appeared of great assistance to airspace people in my company.

I have another question and it concerns the matter of vegetation margin (amount) to be applied in calculation of Minimum Safe Altitude (MSA). I am wondering on what amount of vegetation should be applied for the overall calculation of MSA (obstacle height+ MOC+ vegetation) in case the controlling obstacle is the natural one (DTM)? How the concern looks like in your country or is it a best practice depending on surrounding environment? When I was trained on PANS-OPS course in Toulouse they used to apply 20 meters of vegetation. Is it enough in high terrain with no information on all obstacles with heights of below 100 meters? We have just discussed the matter and came to the conclusion that it would be safe to add an amount of 100 meters for all natural obstacles as it is not required in Poland to report all obstacles (CAA registry of obstacles) with heights of below 100 meters above ground level apart from the obstacles enclosed in ANNEX 14 surfaces. On the other hand, such a move may artificially enlarge the MSA value unnecessarily. However, it could be found convenient to make the procedure start height at or above the highest MSA (ICAO DOC 9368).

Vortilon, procedure designer – Poland

Answer or Commentary:

I. W

It depends on the country the amount of tolerance used for trees and unknown structures. Generally at ASAP we use 30m unless the client specifies a different value. I do not think that there is anything exactly specified by ICAO just the general phrase below.

1.8 CHARTING ACCURACY
1.8.1 Charting tolerance should be added to the height and location of the controlling terrain feature or obstacle when instrument approach procedures are developed. Vertical tolerance is added to the depicted height or elevation of the object.