Frequently Asked Questions
Q: Why make another GPS device when there are already other options on the market?
A: Price, mostly, and expandability. The entire parts list comes out to around $100, while the OpenGauve v1 competes with $300-$400 GPS watches in features. There is another draw though, users can tweak and modify the code and hardware to suit their tastes! You're also not risking an expensive smart phone, and the accuracy is better in most cases.
Q: How is each sensor utilized?
A: The GPS antenna feeds a majority of the information. Starting altitude, speed, heading, distance travelled, and clock are all GPS based. The pressure sensor offsets it's reading with the GPS's altitude when the home point is marked, from there on the pressure sensor measures altitude, rate of climb (variometer) and temperature. With a strong GPS signal, the pressure sensor updates itself if it's reading starts to stray.
Q: What is the battery life?
A: Depending on temperature (sub-freezing reduces battery performance) between 5-11 hours for the full featured v1. Charging should take around 2 hours. The altimeter watch battery life is in excess of 12 hours.
Q: What's next in the OpenGauge project?
A: Very exciting developments are in the works, most namely a base station that wirelessly reports ground wind conditions up to a mile away! Engine temperatures and fuel consumption/quantity are also being wrestled with.
Q: How is the unit mounted?
A: Velcro/elastic straps can be run through the many holes and attached to your arm, wrist, leg, upright, riser, or any other solid object. Alternatively, a sturdy gopro or other fixed mount could be attached to the case by screws or adhesive to suit the end-user's tastes.
Q: Are these available for sale? Can I make one and sell it?
A: Yes! To purchase, reach out to us on the contact page. OpenGauge is open source, with an attribution, non-commercial lisence. This means gauges can be made freely and modified, but never for sale, even if they are modified versions.
Q: Whats the difference between v1 and the altimeter watch?
A: Size, battery life, and GPS. The v1 is larger and has the GPS features including speed, direction, and return to home info. The altimeter watch has the same accuracy in the rate of climb and altimeter as the v1, but no GPS functions.
Instructions
The OpenGauge screen is a 20x4 character backlit LCD, displaying 8 different segments of data. The information and limitations are:
1: Altitude, cycling between AGL (Above Ground Level) and MSL (Mean Sea Level) every 4 seconds. AGL is only accurate compared to the home point, OpenGauge does not sport a ground-following radar at this time. MSL accuracy varies with number of satellites acquired when the home point is set, more satellite signals acquired will lead to a better accuracy. 4 satellites can yield an accuracy of up to +/- 120 feet, improving with additional satellites up to +/- 3 feet. With reception of 8 or more satellites, the pressure offset will calibrate itself to the GPS altitude. Precision is +/- 2 feet regardless of GPS satellite reception. Range is 0-99,999 feet.
2: Variometer, refreshing every 2 seconds. A small window of change in altitude is measured before display, then calculated for change per minute. Because this window of time is fairly small, the variometer will appear to jump around when not in movement. Accuracy is +/- 50 feet per minute. Range is +/- 9,999 feet per minute.
3: RTH, or the Return To Home point, is a compass heading followed by a distance. It is set when the home button is pressed and held for 5 seconds. This will display the direction and distance back to where the home point was set. Accurate to +/- 5 degrees and +/- 0.1 miles. Range is 0.0-99.9 miles.
4: CLK, or clock, is simply the GPS-fetched clock data. Currently, this does not account for time zones or daylight savings time, if applicable, and must be set in the arduino programming. Accurate to 1 second.
5: SPD, or speed, is GPS-based ground speed. OpenGauge does not use a pitot tube or anemometer, so it cannot calculate airspeed. This data should not be used to avoid stalls or never-exceed speeds. Accurate to +/- 1 miles per hour. Range is 0-999 miles per hour.
6: HEAD, or heading, is the GPS-based compass heading calculated by movement. As such, heading will be erratic when stationary up to 2 miles per hour. Accurate to +/- 5 degrees.
7: T is ambient temperature. The barometer used for altitude calculations also included a thermometer for temperature correction, so the data is also displayed on the gauge as a nice-to-have add on. The temperature is measured from inside the case, so it is slow to respond to changes and may be incorrect when the gauge is in direct sunlight or recharging. Accurate to +/- 5 degrees. Range is -99 to 200 degrees
8: GPS is a simple display of the number of GPS satellite signals acquired. More satellite signals will result in more precise and accurate GPS-based measurements. It is recommended to set the home point with as many satellite signals as possible, preferably at least 6. This lower-right section also displays battery percentage when the home button is pressed for 1 second, and a low battery alarm.
Using the gauge is simple. Turn the power switch on at the bottom, and the gauge will start to search for GPS satellites. Once it has found at least 4 satellites, it will start displaying information. Altitude will be inaccurate when first started, this is because the pressure sensor has know way of knowing the atmospheric pressure that changes with the weather.
To correct the altitude, press and hold the set home button for 5 seconds. You must have a reception strength of at least 4 satellites, though more is better, and 6 or more is recommended. The set home button is located on the right hand side of the gauge (or bottom if you have the mini). This button also records the "AGL" altitude and return-to-home heading/distance figures, so make sure you set the home point at your take off point! The home point can be re-recorded as many times as needed before or even during flight. The set home button has an added feature- briefly pressing it for 1 second will display battery percentage and max speed/altitude.
Mounting the gauge is primarily strap-based. We recommend velcro brand elastic straps or similar. Other mounting options, like screws or adhesives, can also be used. Treat the bottom of the case like any other sheet of plastic.
Recharging the guage is accomplished via micro-USB on the left side for the. With the specced battery, charge time should be about 2 hours. Software changes can be made by plugging into the arduino directly on the left side, closer to the left strap rung.
OpenGauge is not waterproof, and while fairly well encased, still has several openings for mounting options and charging. It should not be used in precipitation. Open Gauge is intended to inform the Pilot-In-Command of useful data while in flight. While built with accurate sensors and tested thoroughly, Open Gauge is not an IFR instrument. Piloting aircraft carries inherent risks, and Open Gauge cannot be guaranteed to decrease those risks or relay correct information. Users should not rely solely on Open Gauge to make safe flight decisions. User assumes all risks and liabilities.