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Quote:

Originally Posted by Crumpp (Post 433527)

QNH 1011mb

Thats not an elevation figure, thats just QNH

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you have claimed that airfield elevations change

Where have I claimed this knucklehead?

PLEASE point that one out!!

:rolleyes:

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Thats not an elevation figure, thats just QNH

OMG....

Obviously you have never set an altimeter. Go into your game and adjust the altimeter setting and watch the needles move and the altitude change.......

Quote:

Originally Posted by Crumpp (Post 433279)

Of course, I got my elevation from an aeronautical information site.

Look under METAR and be advised it changes with conditions. It will vary from 597-600 depending on which site you check.

Here it is 600 today:

http://www.checkwx.com/wxmain/fullsite/EGKB

Here Knucklehead......where you say you got it from the hobby website and claimed the elevation changes, it does on your hobby site but an airfields elevation officially remains fixed untill the next geographic survey happens.

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I was taught to set it to the destination from the chart value, while en route and close. I realize it could be advised differently, elsewhere in the world.

Bullsh...t!!!

Quote:

Originally Posted by Crumpp (Post 433531)

OMG....

Obviously you have never set an altimeter. Go into your game and adjust the altimeter setting and watch the needles move and the altitude change.......

QNH is sea level pressure....not airfield elevation, and I can tell you that even if you have set QNH and are sat right on top of the airfield refference point you won't get an exact reading.

Quote:

Originally Posted by bongodriver (Post 433528)

Are you talking about setting field elevation on the pressurisation system? we usually add 100 feet to ensure the cabin is depressurised before touchdown.

No pressure system, Cherokee 140 PA-28-140 fixed gear, two seats designed for training. :grin:

Quote:

Originally Posted by SlipBall (Post 433542)

No pressure system, Cherokee 140 PA-28-140 fixed gear, two seats designed for training. :grin:

OK that makes no sense then, or I believe people here are getting airfield elevation mixed up with QNH....not the same thing, QNH is the pressure setting you set on the altimeter so it reads your altitude above sea level, if you land on QNH then the altimeter will read something close to airfield elevation but not exact, a barometric altimeter is not so precise.
QFE is the pressure at airfield level, it will read close to 0feet +/- altimeter errors when on the airfiled and will give height above aerodrome when flying.
QNE is standard setting (1013) and the altimeter will read your flight level, given that pressure at the surface changes this could be a datum above or below mean sea level.

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claimed the elevation changes

NO, I said the current settings do not agree with the elevation and not all charts are the same.

Why don't you call Jepperson and ask how many elevation changes they make a year on plates and charts.

Here is the Advisory Circular for it.

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This advisory circular (AC) provides general guidance and information for airport authorities in the collection and management of data describing the physical infrastructure, characteristics, and services of their airport.

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If you are requesting to establish or change the Airport Elevation for your airport

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2.5.2 How do you collect the data?
Depending on the level of airport (see paragraph 1.1) the collection of safety critical data requires specialized tools and training. For Level II airports we allow the use of hand held GPS receivers meeting certain standards and following defined processes outlined in this AC. Data collection at a Level III airport requires professional engineering and surveying services to collect and format the data (See AC 150/5100-14, Architectural, Engineering, and Planning Consultant Services for Airport Grant Projects).

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2.5.2.2 Data collection at level I airports
For Level I airports, use the tools and processes Airports GIS provides to capture the location and the necessary attribution describing the characteristics of the feature. The design of the application walks you through the steps to complete the data capture. Review the User’s Guide and complete the on-line training before you use the system to capture data.

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2.5.3 Data accuracy
The accuracy of features at Level I airports is a function of the positional accuracy of the base data set (imagery or map) and associated processes of Airports GIS. Accuracy information using this method will always be an estimated value. Accuracy of features at Level II airports is a function of the post processing of the data to achieve a horizontal position accuracy of 5 feet relative to the North American Datum of 1983 (NAD 83). Data providers must use latitude and longitude as the unit of measurement. The vertical position (elevation) requirement is 10 feet relative to the North American Vertical Datum of 1988 (NAVD 88) with a unit of measurement of feet. AC 150/5300-18 contains the accuracy requirements for Level III airport data.

http://www.faa.gov/documentLibrary/m...50_5300_19.pdf

When you make a map, there is large room for error both horizontally and vertically. That is why there is so many different datums and it is extremely important you are on the same datum as others in the system.

That is why aerial navigation is by convention.

In fact, Verticle Datum has been one of the most problematic areas in navigation until recent technological advances. Those advances is what allowed us to put JDAM's into multiple cave entrances on the side of a mountain in 2003.

http://www.usna.edu/Users/oceano/pgu...L%20DATUMS.htm