NOT all Acoustic Targets are created equal!
Due-diligence uncovers critical differences between targets.
The following non-technical document, explains design differences affecting target accuracy.
Acoustic E-Targets fit into 3 – Distinct Categories.
A: Open-Faced target, with 4 sensors or 8.
- Sensors are mounted externally on the front frame of any target, or several feet in front of the target.
- Requires calibration by a competent user before use, and at each yardage for “best precision”.
- Maximum coordinates = 4 per virtual plane.
B: Closed acoustic 4 sensor box.
- A manufactured frame (similar to a door frame).
- The front and back sealed with a rubber membrane.
- Better environmental control of shock waves.
- Maximum possible coordinates = 4.
C: Closed acoustic 8 sensor box.
- A manufactured frame. 2 sensors per side x 4 = 8
- The front and back sealed with a rubber membrane.
- Coroplast Plastic front and back covering rubber membrane.
- Maximum coordinates = 56.
So the BIG Question you need answering is:
Will, I be happy trusting my score, record,
and cost of my hobby to 4 coordinates or 56 coordinates?
If you answered 56? THEN READ ON
The physics of E-Targets:
Precision affecting factors.
- Trajectory: The pressure cone is much like the waves created by a moving boat across a lake. If you placed 2 buoys 50 yards apart and you split them at midpoint the waves would hit the buoys at equal times.
- HOWEVER: If you do the same thing across a river, the buoy up-stream will catch the wave later than the downstream buoy. Maybe much later, maybe not at all depending on the current.
- The pressure wave comes off the projectile in an equal conical fashion but is affected by the environment, such as bullet weight, speed, and speed of the cross-current.
- When the bullet hits the target at 200 yards, the sonic waves are near perpendicular to the target. Therefore, all hit the sensors at a legitimate time. That picture changes at 300, 400, 500 ……..1000yards…..to infinity. Therefore, the pressure cone and/or trajectory angle are not appropriate for the sensors.
- WIND: Sonic pressure waves are equally provoked by environmental conditions. Humidity, altitude, temperature but MOSTLY WIND. Try talking into the wind to someone.
- Target angle: Really messes with open targets!
- All acoustic sensors (ears) “hear” all environmental sound waves, including from adjacent lanes.
- Individually they are incapable of determining distance, or the direction from the source of the sound.
NB – critical point: It takes 3 sensors to provide 1 Point Of Impact.
- Ever-present illegitimate sounds (gossip) in the electronic environment surround e-targets. This “gossip” results in ERRORS! click for a technical report.
- 1) LOST SHOT – nothing recorded. HEXTA >Eliminated
- 2) GROSS ERROR – inaccurate shot placement. HEXTA >Eliminated
- 3) GHOST SHOTS – sonic snaps from adjacent lanes. HEXTA > Eliminated
- Each sensor records the time that it “heard” a sound. The time lag between when one sensor “hears” the sound, and when another sensor “hears” the same sound – creates a data-point. 2 Sensors = 1 data point, but NOT a co-ordinate.
- A MINIMUM of 3 sensors is required to calculate a co-ordinate!
- When 1 sensor in a 4 sensor target does not report accurately, you have an AVERAGE of 1+1+1=1 co-ordinate. Incapable of PRECISION!
- The Software receiving the data from the sensors must be able to decipher good data from the gossip. The software has to identify which sensor is erroneous in its reporting, and either, 1) apply correction to it, 2) eliminate its data point if the error is unacceptable, or 3) function without the data as in when a sensor or wire gets shot out.
- Magnitude of Scenarios that affect precision.
- Wind: a 12 mph @ 1200 fps = 2” sonic wave bend
- Trajectory, tilted target, or range:
- 2 degrees at 1200 fps = 3”.
- 5 degrees at 1150 fps = 14”.
- Adjacent shot interference.
- Insufficient redundant data.
Summary: Acceptable Precision requires: sufficient sensors, collecting enough “data points”, allowing the background software system to collect, audit, double check, and backup each sensor’s data to assure the most precise co-ordinates for bullet point-of-impact.
A Closer examination of acoustic target systems.
Identify each sensor.
|Sensor ID A||B||C||D|
REMEMBER: We need minimum of 3 sensors to conclude one co-ordinate or trilateration.
A 4 SENSOR system can provide a MAXIMUM possible 4 co-ordinates.
If 1 sensor records bad information or gossip, imagine that sensor “
B” failed. What effect does that have?
A, B, C
You have ONE co-ordinate.
Just ONE Co-Ordinate calculation. Not enough for accurate bullet point of impact. This results is either a 1) LOST SHOT, or 2) a GROSS ERROR
A LOST SHOT is pretty obvious.
A GROSS ERROR puts bullet impact in the wrong spot. That’s serious! NOBODY KNOWS IT – It’s recorded for record.
The critical questions are
How PRECISE do you want an E-Target be, to “GO FOR RECORD”.
What is your Non-Negotiable, a) price, or b) precision?
If the non-negotiable is precision, then read on.
HEX Systems and goBallistic introduce –
HEXTA Match-Grade Targets
WHERE EVERY SHOT COUNTS!
What does a Match-Grade Target require?
- Sufficient redundant data, for co-ordinate calculations to conclude POI. Accomplished ONLY with sufficient sensors.
- FULL TIME CALIBRATION: Software capable of recognizing and rectifying all the unacceptable and/or erroneous sensor readings. With enough data, the software can recognize that a sensor is consistently in error by “x” amount (i.e. 2.46 inches) and correct it. Or if it’s grossly wrong (as in being shot out) the software can eliminate it altogether, without interrupting the shooter.
Redundancy = precision!
The HEXTA – 8 sensor advantage
How more sensors make a target more precise?
|# of Sensors||# of co-ordinates|
- 56 co-ordinates allow us to identify a sensor that missed a shot, and if it continues to fail, we can cut it out of the calculation.
- It allows us to identify a sensor that consistently calculates errors in measurement, and applies a correcting factor to the sensor.
- 8 Sensors allows us to accurately position every shot with Maximum Precision!
How PRECISE is our
HEXTA Match-Grade – 8 sensor target?
Objective, scientific, testing demonstrates typical Standard Deviation on 2 MM, or less.
Simply, math! An 8 sensor target, allowing 56 co-ordinate calculations, has to be far more precise. It is inherently more precise. It takes 8 sensors and a sealed target to eliminate the sonic cone shift due to wind, and Ghost shots”. It takes 8 sensors to compensate for trajectory angle. It takes 8 sensors to calibrate out Gross Errors, or Lost Shots.
All acoustic targets should be on-site tested, at various distances, and crosswinds. Check our TESTING research. That’s repeatable. We require at a range demo, that the range conducts a test to measure the PRECISION. When HEXTA targets are installed at a range, we will test them with you. ALL Vendors should provide that information!