Terrain maps "lowest terrain"??
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Terrain maps "lowest terrain"??
On our terrain maps we have two figures. The highest peak on the scale and the "lowest" terrain. What is the idea behind that? If I have a 500´ "lowest" hill there is very likely also 400' 300' and lower terrain. Could this be to give us the idea of the countour, i.e. 12000' /400´ would mean a mountainous terrain while 12000´/11000´ could be more like a plateau?
Does anybody have a clue?
Does anybody have a clue?
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"Peaks" is an optional feature of the EGPWS. It's main purpose is to provide greater situation awareness of terrain features when at cruise altitudes in case of unplanned desents. Without the peaks feature activated, terrain is only displayed within 2000' of the aircraft altitude.
Honeywell has an excellent website dedicated to EGPWS, www.egpws.com, where you can even download a Pilot Guide, amongst over goodies.
Honeywell has an excellent website dedicated to EGPWS, www.egpws.com, where you can even download a Pilot Guide, amongst over goodies.
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The 'lowest' figure is the lowest terrain as displayed (in green, hopefully) on your screen. All black bits are lower than said figure
Last edited by Gary Lager; 15th Aug 2005 at 17:43.
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I´m aware of the function of the system, I am, however, speculating on the purpose on having the "lowest" terrain value displayed. To date I haven´t come to any conclusion, except that it may be there to give the idea of the wheather I´m flying over i.e. a plateau vs. valleys and mountains.
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I must admit, I was confused by the relevance when I first came across the function - I suppose you can't have the whole screen 'green' - that'd be daft, so there must be an rule such as: "50% of all terrain is higher than this altitude" for instance, so you get an idea of where the highEST bits are around you (relatively speaking).
Of course you alwys know that you can descend to the 'highest' altitude safely (taking into account FMC position error etc etc), but if you're over a 'black' bit you could descend to the 'lowest' dsiplayed altitude safely.
Not much use that I can immediately see apart from that, and, as you suggest, to give you general situational awareness of the surrounding geography.
Flying with yellow & red bits on the screen is where the extra terrain awareness is really appreciated, of course, which is what the system was primarily designed for.
Of course you alwys know that you can descend to the 'highest' altitude safely (taking into account FMC position error etc etc), but if you're over a 'black' bit you could descend to the 'lowest' dsiplayed altitude safely.
Not much use that I can immediately see apart from that, and, as you suggest, to give you general situational awareness of the surrounding geography.
Flying with yellow & red bits on the screen is where the extra terrain awareness is really appreciated, of course, which is what the system was primarily designed for.
