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J3GQ
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| Joined: | Fri Nov 21st, 2008 |
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| Posts: | 4 |
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Posted: Sun Nov 30th, 2008 09:31 pm |
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Hello,
My brand new 430W (software version 3.1) shows a strange behavior when flying low (say 300- 400 ft) over wind turbines/ generators. When approaching the wind mill a yellow cross is shown on the 430W´s display. When getting closer (say within 0.5 miles) without changing altitude the cross turns red. This is odd in several ways:
- the crosses (yellow or red) are not explained in my user handbook at all, obstacles are supposed to look like little towers,
- red symbols (as a warning of a potential impact) should never be displayed when 300+ ft higher (and can be quite disconcerting when flying in restricted visibility)
- and finally, how can yellow turn into red when the aircraft (and the towers) don´t change their altitude during the close encounters ?
Any ideas and suggestions welcome, and would very much appreciate if anyone could confirm my observations. Unfortunately I can´t offer any screen shots or photos.
Rgds - J
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rkaplan
Administrator
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Posted: Sun Nov 30th, 2008 09:49 pm |
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| Well considering that FARs prohibit flight within 500 feet of any structure and given the advisory nature of the terrain software, the behavior you report from the GPS seems fine.
____________________
Richard Kaplan, CFII
rkaplan@flyimc.com
http://www.flyimc.com
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J3GQ
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| Joined: | Fri Nov 21st, 2008 |
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Posted: Mon Dec 1st, 2008 05:44 pm |
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In all fairness, this doesn't even explain a single one of the three points mentioned in my post. Are you sure you took the time to read it carefully ? BTW it doesn't explain why the Garmin 496 on board didn't behave this way ... but simply did what it was supposed to do.
Anybody else any experience ?
Kind regards - J
PS: checked my track logs and the mapped obstacle heights. So the exact altitudes were 372 ft (MSL max.) and 920 ft (MSL min.)
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rkaplan
Administrator
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Posted: Mon Dec 1st, 2008 05:47 pm |
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GPS vs. barometric altimetry could explain a number of your observations.
The GPS engine and software are not the same in the 430 vs. the handheld GPS, nor is the antenna the same, so some variation is expected with respect to both altitude and location.
I think you are trying to attribute a level of accuracy and utility to an advisory terrain system which is beyond its intent.
____________________
Richard Kaplan, CFII
rkaplan@flyimc.com
http://www.flyimc.com
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