www.pilotballoon.com "the pilot balloon web resource" 


Pilot Balloon - Flight Calculator

Observations of a pilot balloon ascent made by an optical theodolite are solved for wind speed and direction by this Java Scripted Page.  This page may be saved and used off line.

Information used in this page and the java program was sourced from a page created by Ross Marsden and used by permission.  I edited some content, but make no personal warrantees of any kind for this program and I was not involved in the creation of the coding of the calculations.   

Select or enter the Input and Output Options, and enter the theodolite readings in 3 columns; time in seconds (starting from the first reading), azimuth (either in degrees Magnetic or True), and elevation.
An example set of readings is given; press 'Clear' and replace with your own.
Input Options
Azimuth: degrees Magnetic True
Magnetic Variation: degrees True
Ascent rate: feet/min meters/sec
Output Options
Direction: Bearing Reciprocal
in degrees Magnetic True
Speed: knots meters/sec
Height: feet meters

Theodolite readings

tim azim elev
Pilot balloon computed winds

How to use the Pibal Theodolite Pilot Balloon Flight Calculator

  1. Fill the pilot balloon to a known ascent rate. Release the balloon and observe it at 1 minute intervals. When you can no longer see the balloon, abandon the flight. Hit the Clear button to clear the data in the readings box above. Key the observation's time, azimuth and elevation data into the Theodolite Readings box.
  2. Enter or select the various options in the Input and Output sections, and hit Compute.

Input Options

Azimuth - Indicate where the azimuth is referenced to; 0 degrees Magnetic, or 0 degrees True.
Magnetic Variation - What is the Magnetic Variation at your location; the True bearing of Magnetic North?
Output options
Direction - Wind direction can be expressed as the direction the wind is coming from (bearing) or the direction towards which it is going (reciprocal).
Speed - Wind speed units can be either knots or meters per second.
Theodolite readings
Ascent rate - You need to make an assumption about the ascent rate of the pilot balloon so that it's position can be fixed in the vertical; a direction and speed computation for each time interval can then be carried out.
Time, azimuth and elevation
Starting from the first reading (not the trivial one at time zero), enter the time in seconds, and azimuth and elevation in degrees, separated by one Space (not Tab).
Off line use
It is not necessary to be connected to the internet to use this utility. Here are two ways to make this available off line.
A.   In IE, add as a Favorite and check the "Make Available Offline" box. Netscape Navigator does not provide the available offline facility.
B.   A better way is to save the document to your disk . . .

  1. Right click in the page and select "View Source" (or obtain View Source by whatever means your browser provides).
  2. Select All and copy it to the clip board.
  3. In your favorite text editor, open a blank document and pasted from the clipboard.
  4. The only condition is that you leave the credits for Test Data and Source below.
  5. Save to somewhere you can find it again. Bookmark the file in your browser for use at any time, any place.

Test data
The example theodolite readings are at one minute time intervals for the first 5 minutes, then every two minutes to the end of the flight. It is a set of training data to test the program. It was kindly provided by Tony Shaw of Meteorological Service of New Zealand Ltd.
Sourced from...
Balloon Met and Science by Ross Marsden.  This page created by Martin Brenner 9-2000