Excel Direction Finding Program

by Paul Ternlund, WB3JZV

note: to train folks so that they might easily fit into this system, Paul wrote a paper describing how this was all supposed to work.

The Tracking & Recovery team use a standard map and grid system. They take bearings at fixed times and report them by radio for entry into an Excel spreadsheet. A speedy and accurate balloon position estimate is the principal result.

The spreadsheet, running Augmented Triangulation Software written by WB3JZV, assists the tracking process in four areas:

  1. Triangulation
  2. Position estimation
  3. Plotting
  4. Station performance monitoring

This is implemented with custom macros for Microsoft Excel.

During triangulation, the spreadsheet calculates a point for each unique pair of bearings by solving trigonometric equations.

During position estimation, the spreadsheet determines a best guess for the balloon�s position from the scattering of the triangulated points.

Twenty bearings at one sample time can produce 190 points. In the real world these points do not superimpose. This is typically due to poor bearing accuracy that can be caused by signal multipath, improper location of beacon signal maximum, poor tracker positioning, etc.

During plotting, the spreadsheet uses the excellent scatter charting capability of Excel to show the relative positions of all the trackers, the triangulated points, and the estimated balloon position for each sample time.

During station performance monitoring, the spreadsheet records each time a station�s bearing is ignored because it diverges from another�s, or it produces a triangulated point deemed too far from the main point cluster.

We generally request bearings be taken by members of the Tracking and Recovery Team on a mark given every 15 minutes during ascent, and then approximately every 5 minutes when the payload is descending and close to touch-down. It then takes about 2 minutes to collect and enter the data, and another 2 minutes to calculate the balloon�s position estimate using the spreadsheet.

I wrote the software for Edge of Space Sciences, Inc., Denver, CO, to help track and recover helium-filled balloon scientific payloads. In 1993, I implemented the software using Microsoft Excel Macro Language, originally for use on an Apple Macintosh. In May-June 2001, I re-wrote most of the Macro using EXCEL VBA. It can run on both Mac and PC platforms.

My technique was reviewed in the March and April 1993 "Homing In" columns of 73, Amateur Radio Today; and was also published as a sidebar in August 1993 QST, "RDFing with a Notebook Computer," pages 36-7.

The latest version provides immediate feedback to each tracking team member in the form of bearing error for a given sample time. This calculation is based on the payload's GPS fix at the same sample time.

 

Here is the old version of Paul's spreadsheet.

Paul has modified his program. The current version isn't available but... here is some of the generated information it provides: