Comments on: How to use a DSLR as an altimeter

By: Dennis Wright

Dennis Wright — Thu, 07 May 2009 08:57:17 +0000

Thanks Simon, I’ll follow your exploits and good luck.

Dennis

By: simonpbarlow

simonpbarlow — Thu, 07 May 2009 08:42:41 +0000

Hi,
I am a photographer that flys… in July this year I’m doing the FAI Round The World flight with a fellow pilot… check out http://simonpbarlow.wordpress.com/

Cheers

Simon

By: Dennis Wright

Dennis Wright — Thu, 07 May 2009 08:38:57 +0000

I don’t believe my calculations could be that precise. It was just something I did for my own curiosity and amusement, and was amazed the result came out anywhere near 10,000ft never mind that close.

It sounds like you’re a photographer who does some flying. If so, you’re a lucky man to be able to be involved in both those activities.

By: simonpbarlow

simonpbarlow — Wed, 06 May 2009 23:12:38 +0000

Hi
Nice bit of maths!
You also need to factor in that for every 1Mb of pressure change equates to about 30ft of altitude. Aircraft altimeters are set to the pressure setting in the area (QFE) or region (QNH) or a “standard” which is AMSL (Above Mean Sea Level) 1013Mb if flying above a transition altitude for certain flight rules. (usually 3000 ft)
So the 9,960 feet calculated could be reported as 10,000 on the aircraft altimeter if the pressure setting was 1Mb different than the 1013Mb standard. (Which incidentally is the pressure setting that is used when aircraft fly on flight levels not altitude)

Cheers

By: Dennis Wright

Dennis Wright — Wed, 06 May 2009 18:02:06 +0000

An interesting aside is that with a 250mm lens and an APS-C sensor, 1 pixel corresponds to an object just under 3 inches in size which is 10,000 ft (1.9 miles) away.