Recap of EOSS-54

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Results from the Triangulation Program

1 March 2002


  • The Tracking and Recovery Group comprised 5 DF teams
  • There were 6 sample times executed
  • The best overall team performance came from KC0CNT with a 6 degree average LOB error
  • The average T&R group performance was 14 degree error
  • For the final report, some calculations were repeated on request using a corrected position or bearing as noted
  • Separations in miles between GPS and the T&R group fixes ranged from 18.2 miles (first sample) to 2.9 miles (6th or final-most important sample)
  • An LOS error of 2.9 miles relates to an 8.41 square mile of uncertainty. The latter is well within the program's goal of a 100 square mile search area.
  • In general, average tracker bearing errors were too high (14 degrees). T&R teams are encouraged to practice on known targets to validate their hardware and technique.
  • Since the average tracker bearing errors were so high, perhaps the beacon presented added difficulty(?)
  • KC0CNT indicated he used a 9 degree declination for all 6 samples based on his GPS receiver. After careful review of web-based declination calculators from official government agencies, I believe 9 degrees is closer than the 11 degrees we typically use for "down east" recoveries. So, I re-ran all 6 samples using 9 degree declinations for all stations. The results were 10 bearing errors reduced, and 7 increased. I noted that one station was involved with 4 of the 7 times where there were increased bearing error, and this station also posted the largest average tracker error. Therefore, I suspect there may have been some technical problem with that station.

FYI, the Triangulation Program is designed to provide a good fix when most (more than half) of the LOBs are "good" for a given sample time. The goal is to obtain our final fix to within 100 square miles of shuttle touchdown (that is within about a 10 mile by 10 mile area). The following is true...

  1. Single-digit bearing errors are better than double-digit
  2. When a station has multiple double-digit bearing errors, it is likely the station is having equipment and /or technique problems.
  3. Every station will encounter LOB errors some time for many reasons.
  4. The greater the participation (i.e., the more LOBs submitted) for a sample time, the better the chance of a good fix resulting from the program.
  5. Once in the field, prior to a launch, a DF team may request an LOB test to my station to practice/validate a DF process.

On future flights, I recommend we use the declination for the estimated touchdown area-and that we allow the triangulation program do the math and add the declination for all stations. Then, stations can more simply pass their LOBs (i.e., X,Y and B, where B is "magnetic" vs. "true" as provided directly from the compass reading).

73, de Paul, WB3JZV

Charts and Tables

Captured from Paul's Excel Spreadsheet available here

Bearings by 11� declination

Bearings actually used during the recovery

Bearings Corrected by  9� declination

Comparison 9� and 11� declination