Frequently Asked Questions

 

1) What equations are used to calculate the Density Altitude?

All of the equations and algorithms used in my Density Altitude calculators are fully described in gory detail on my Density Altitude web page. Just start at the beginning of that article and collect equations until you've solved for the Density Altitude.

 Note that if you want a very simple method which still gives the same values of Density Altitude as reported by US ASOS/AWOS stations at airports, see the Simpler methods of Calculation section.

2) How is the Dyno Correction Factor calculated?

All of the equations and algorithms used in the Dyno Correction calculator are fully described in gory detail on the Correction Factor web page.

3) Why don't these calculated density altitude values agree with the density altitude reported by my local ASOS/AWOS-3?

Currently, the ASOS/AWOS-3 stations (automated weather observation stations located primarily at airports all around the US) do not include the moisture content of the air in their density altitude calculations. You can approximate their calculations by setting the dew point (or relative humidity) in my calculators to a very low value.

4) Why does the calculator show a negative density altitude?

If the calculated air density is greater than the standard sea level air density, the calculator will show a negative altitude, that is, an altitude below sea level, which is merely the result of a mathematical extrapolation of the standard atmosphere, even though such an altitude may not actually exist in free-air.

Technically, the standard atmosphere stops at sea level, but in these calculators the ISA equations have been extrapolated into negative altitudes in order to demonstrate the effects of non-standard conditions (such as extremely cold weather) on the air density.

5) Can you send me an Excel spreadsheet with these calculations?

No, but you can easily go to the Technical Article pages (see the links provided in items 1 and 2 above) and write your own spreadsheet program (or any programming language of your choice) using the equations and algorithms that I've carefully described for you in gory detail .
 

6) Can I use the calculator when I'm not connected to the internet?

Yes, the calculators do not need an internet connection to perform the calculations. So, you can simply load the desired web page while connected to the internet, then put the computer to sleep, travel somewhere, wake up the computer and continue using the calculator. Or, better yet, you can save the entire web page to your hard drive or flash memory to use anytime, anywhere, as described below:

Saving web pages:

With many web browsers it's very easy to save any of the calculators on your computer or mobile device. In fact, virtually any web page from any web site can be saved on your computer.

Chrome, Firefox and the Chromium-based Edge all make it quite easy to save any web page which can then be viewed off-line in any browser at any time.

If you're using Chrome, Firefox or the new Edge:

Go to the web page that you want to save.. and simply hit "Ctrl-s".

Then the Save As dialog box will then pop open... Choose a file name and location that suit you, and select Save as type: Web Page, Complete.. then click Save.

Presto.. the web page is now stored on your computer and can be run anywhere, anytime (as long as Javascipt is enabled).

For mobile devices, many of the current web browsers do not offer an option to save the entire web page for offline use, so you may need an additional app to save the web page (including the Javascript) for offline use. For example, for Android, the "Offline Browser" app seems to work fine with all of my calculators (as of Oct 2014).

Apps for iOS and Android:

There is an iPhone/iPod/iPad app called DenAlt, created by Marcus Staloff, available in the Navigation section of the Apple Apps store which uses these same density altitude equations. And there is an Android app called Density Altitude Calculator by Rick Lettlow which also appears to use my equations.

7) Can I run the calculators on my iOS, Android or Blackberry mobile device?

Yes, any of the calculators can be run on any smart phone, or any other digital appliance, which has a JavaScript-enabled web browser.

You can either run the calculator in your web browser using an internet connection, or you can run the calculators "off-line" by saving the complete web page to your mobile device or using an app as described in item 6 above.

8) Can I put the calculators on another web site?

No... Please don't. From time to time I make changes and improvements in the calculators, and I want all users to be able to come to this web site in order to use the very latest, most accurate versions of these copyrighted calculators.

As alternatives to putting any of my calculators on your web site: you can simply open my calculator page in an iframe on your own web page, or open a new browser window to display my web page in that new window, or you can just give your users a link to my web page.

All of the calculators are copyrighted, and are made available for use on this web site solely for an individual's own personal usage.

9) General copyright statement for all of the calculators

Copyright © 1998-2023 Richard Shelquist All Rights Reserved

The calculators on this web site, including all JavaScripts and programming code, are the copyrighted intellectual property of Richard Shelquist. The calculators may be freely used for an individual's own personal use via my web site, or by means of one copy on an individual's own computer for personal use, but no portion of the calculator may copied or republished in any form on any web site, bulletin board, computer network, or any other means.

 

updated 23-Jan-2023