14 Altitude Data

All entries in any event for which an achieved altitude figure is scored shall be tracked in flight by theodolites of a design approved by the NAR Contest Board. Any tracking theodolite that:

Is equipped with both azimuth and elevation axes at right angles to each other
Can be leveled or adjusted to an otherwise proper plane before use
Has an accuracy of 0.5 degrees in both azimuth and elevation
Uses a rifle-sight or equivalent optical sight with or without lenses, or uses a pair of open sights mounted at least twenty centimeters apart
Uses crosshairs in the optical or open sight
Is mounted on a sturdy tripod or other solid base in a manner that does not permit the tracking head to wobble or otherwise lose its zero-reference under normal use
Has a provision for securely holding the sights firmly in any desired position, so that the operator may accurately record the tracking data associated with a flight
Is capable of tracking to an azimuth of +/-180 degrees and an elevation from 0 degrees to 90 degrees

shall be acceptable for NAR contest use.

The Contest Board must approve theodolites that do not meet all of the above requirements before they may be used in a sanctioned activity.

14.2 Baseline

Two or more tracking theodolites shall be used on appropriate baselines. The baseline should be between 50% and 400% of the expected altitudes to be tracked. Thus a 300-meter baseline would be appropriate for 75-600 meter flights. While very low power events may require a baseline under 300 meters, proper care and judgment should be used before this is done. Longer baselines are strongly encouraged for high-powered or high-performance models. Proper baselines must be used to track any record setting flight.

14.3 Tracking

Models shall be tracked to apogee if practical. When apogee tracking is used, one person shall be designated to give a mark to the theodolite operators at precisely the instant the entry appears to reach apogee, and the theodolites shall be locked at the mark. At the discretion of the Contest Director, models may be tracked to ejection instead of apogee. When ejection tracking is used, it is recommended that the models to be tracked contain colored tracking powder to create a visible cloud at ejection, and that the theodolite operators lock their theodolites at the appearance of the tracking powder cloud. It is further recommended that all entries that are to be tracked be painted in colors or patterns that will aid tracking. All entries in an event shall be tracked using the same tracking method (either apogee or ejection).

14.4 Communication System

A reliable voice communication system shall be used to link both trackers and the launch control area, for the purpose of calling marks and for the transmission of tracking data.

14.5 Data Reduction

Angular data obtained from theodolite tracking shall be reduced to an achieved altitude figure by means of a standard system of equations approved by the NAR Contest Board. Samples are included in Appendix E. All data shall be recorded for all altitude events and flights, including those flights that may be disqualified; this permits the altitude data to be available in case the disqualification ruling is later reversed.

14.6 Error Check

The error figure as computed by the approved equations must be less than or equal to 10% to be considered valid and acceptable for competition and record flights. Flights whose reduced altitudes do not satisfy this constraint shall be scored as Track Not Closed. Flights whose data is incomplete, preventing calculation of their altitude, shall be scored as Track Lost. All altitudes shall be rounded off to the nearest meter. Fractions of a meter less than 0.5 must be rounded to the next lower meter; fractions 0.5 or above must be rounded to the next higher meter. The rounded altitude shall be the official scored altitude. Any altimeter reading reporting by an entry that was optically tracked using theodolites will NOT by officially considered and Rule 14.9 will NOT apply.

14.7 Multiple Stations

When multiple-station or parallel systems are used, it is only necessary that one pair of trackers (one at each station) close. In the case that more than one pair of trackers close, the official altitude shall be computed by averaging all closed tracks, and then rounding them as above. The averaged rounded altitude shall be the official scored altitude.

14.8 Novel Methods

The NAR Contest Board must approve novel altitude determination methods before the results are accepted for competition.

14.9 Untracked Flights

Track Lost or Track Not Closed, if it is not disqualified for any other reason, is considered an unofficial flight. In this case the contestant is entitled to an additional flight, to be made during the period allocated for tracked flights. At the option of the contestant, Track Lost or Track Not Closed may be considered an official flight if it is not disqualified for any other reason. In this case the flight cannot place but shall receive flight points; except in an event where the score is the sum of several factors, in which case the flight shall be scored as having an altitude of zero.

14.10 Electronic Altimeters

The use of theodolites will remain the preferred method for altitude tracking, (as described in Rule 14.1). Approved electronic altimeters may also be used. All entries at a sanctioned meet are to be tracked using the same method. The sanction request form submitted by the contest director must state under "Special Provisions" whether will fly using "Theodolites (14.1)" or "Altimeters (14.10)". The contest director will also assure that all announcements and publications for the sanctioned meet will tell all prospective entrants the same.

Only commercially available altimeters approved by the NAR Contest Board and publicly announced as approved at least 60 days before any contest where they are used may be used in competition. These altimeters may not be altered or modified in any manner, including power source changes. An altimeter must meet the following requirements to be approved by the Contest Board: Uses barometric measurement techniques to record relative flight apogee altitude above launch pad altitude. Resolution of 2 meters or better in readout. Accuracy 2 percent of recorded altitude or 2 meters, whichever is greater. Sampling rate of 10 per second or greater. Audio or visual readout directly from the altimeter. Capable of being zeroed of previous flight data before flight.

NAR Contest Board approved altimeters are listed in Appendix G.

14.10.1 Safety Check-In Procedure: The flight ready entry with the altimeter removed must be presented to the safety check official for inspection to verify the altimeter is unaltered and has been zeroed. The safety check officer may request the "owner's manual" for the altimeter if any questions arise concerning its operation or post flight readout. The make and model of the altimeter will be noted on the contestant's flight card under the "remarks" section. The altimeter's power source will be turned on in the presence of the safety check official, and zeroing will be verified after boot-up.
The altimeter will now be placed in the model and secured in the presence of the safety check official. The entry is now ready for pad assignment.

14.10.2 Launch: The RSO or contestant will verify immediately prior to countdown that the altimeter is in "stand-by" mode.

14.10.3 Returns Procedure: The model and altimeter must be returned as recovered, unopened. The returns official and contestant both will concur on the reported altitude. Any other specific event rules may also apply.
If the altimeter can NOT be returned, and the model is not DQ'd for any other safety or event rule violations, then that flight can be considered "Track Lost" and Rule 14.9 can be applied. If the altimeter fails to report an altitude, and the flight has not been DQ'd for any safety or event rule reason, then that flight can be considered "Track Lost" and Rule 14.9 can be applied

14.10.4 Performance Records with Altimeters: NAR performance records for entrants using electronic altimeters will NOT be kept in any event classes and age divisions per Section 17.

Return to the NAR home page | Join the NAR