What is GliderLink?

GliderLink is a free app for team soaring. It shows the locations of gliders around you on a moving map. You can see their callsign, relative altitude, and vertical speed. With a glance, you can see where your friends are, and whether they’re in lift.

What is team soaring?

Team soaring is when multiple gliders fly together and share information about the lift they find. A group of gliders can be much better at finding lift than a single glider, because they can spread out and search over a large area. Typically, pilots use the radio for sharing information. It can take quite a few words to explain to someone else where you are, and the terrible audio quality of analog radios often makes understanding what is being said a real challenge. With GliderLink, all it takes is a glance at a screen.

How does it work?

Cellular reception is often unavailable in the air, either because the glider is too high up, or flying in a remote area. Instead, GliderLink uses a device called a goTenna Mesh, which pairs to your phone/tablet using Bluetooth, and contains a separate radio that it uses to communicate with other goTennas. It’s like a peer-to-peer airborne datalink. GliderLink uses the goTenna to directly send your GPS coordinates to other users of the app; once every 20 seconds. No cell towers, base stations, or servers are involved. You can put your phone in airplane mode, and still use the app and goTenna. GliderLink and its creator have no affiliation with goTenna, Inc.

How much does a goTenna Mesh cost?

They retail for about $72-90 each (in 2018), depending on how many you buy at once (idea: organize a group buy with your club). You can buy them from goTenna, or in outdoor stores like REI. Note that GliderLink uses the goTenna Mesh, not the original goTenna or the Pro. You can save $20 by ordering a goTenna Mesh from this link: https://www.talkable.com/x/IgisuY. This is their standard referral program, and I get a small reward from it. It would be a nice way to say thanks for the app.

What is the range of the goTenna Mesh?

Reception is fairly reliable within about 10 miles, air-to-air. This is quite adequate for team flying, and is much better than Flarm. So far, the maximum distance I’ve seen is 53 nautical miles (61 miles), but the reception is not reliable at that range.

How goes GliderLink compare to Flarm?

Flarm is a good system for collision avoidance. It broadcasts your GPS coordinates once every second, and can warn you if you and another aircraft are on a collision course. GliderLink broadcasts your GPS coordinates once every 20 seconds. This is enough to keep you updated on who’s nearby, but it is not enough to yield a useful prediction about collisions. One advantage the goTenna Mesh, and GliderLink, have over Flarm is better range. Flarm transmits at less than 20mw, while the goTenna Mesh transmits at 1W. GliderLink’s superior range makes it useful for team soaring. A goTenna Mesh is also a much cheaper than Flarm ($1600USD), and is certainly better than nothing for collision avoidance.

Will there be a iOS version?

Yes, probably. It will take some time, but I consider it a high priority.

Can you integrate this with XCSoar or TopHat?

It is certainly possible, and I think that would be great. Looking for volunteers!

What do I need to run GliderLink?

You need a goTenna Mesh and an Android phone/tablet that runs Android 4.3 or above, and has Bluetooth LE (aka 4.0). These are required by the goTenna Mesh. It helps if the phone has a bright screen, for sunlight readability. In my experience, recent Samsung phones with OLED displays are very bright and are reasonably readable in sunlight.

What do the numbers mean next to the glider icons?

On the upper left of the glider icon, the callsign is shown. This can be the tail number, contest number, or the last two or three characters of the registration; whatever the glider is known as. It should not be the pilot name or initials. On the lower left is the glider’s relative altitude, in hundreds (feet or meters, depending on settings). For instance, +54 means the other glider is 5,400 above you. On the right side of the glider icon is their vertical speed. If the units for vertical speed are set to ft/min, then vertical speed is shown in tens (300ft/min would be shown as 30). The arrow indicates up or down.

What do the colors of the gliders indicate?

Your glider is shown in blue. Other gliders are shown in green if you have received a position update from them in the past 20 seconds. They turn orange if you haven’t received an update in the past 20-60 seconds, and they turn red if you haven’t received an update in over 60 seconds. The glider will disappear from the map if you haven’t heard from them in the past 5 minutes.

How can I see the distance to other gliders?

You can tap on a glider to get more information like distance, ground speed, and exact altitude.

Why aren’t there maps available outside the USA?

Sorry about that. Working on it.

How does the mesh feature work?

Starting with version 1.2.0, GliderLink will broadcast not only your own location, but the locations of up to three other nearby gliders. This increases the range and robustness of the system.

Example of extended range: You are glider A. Glider C is far away, out of range. However, glider B is between you and C, and in range of both of you. When C broadcasts its location, B will see it and re-broadcast it, which you can then receive. In effect, you will be able to see gliders that would normally be out of range.

Example of increased robustness: You, glider B, and glider C are all within range of each other. When glider C broadcasts its location, the fuselage happens to be blocking transmission to you, but not to glider B. Glider B sees glider C and re-broadcasts C’s location. This time, you are able to receive C’s location since your line-of-sight is not blocked to glider B. There is more than one path for C’s location to get to you, so the system is more robust. The more gliders there are in range, the most robust the system is. One caveat is that C’s location may get to you a bit later, since you have to wait for glider B to broadcast on its usual 20 second cadence.
Can a lone goTenna Mesh be used as a mesh relay for GliderLink?
Unfortunately a lone goTenna Mesh can’t relay transmissions from GliderLink. It must be paired with a phone running GliderLink. GliderLink doesn’t use goTenna’s mesh networking implementation; it uses its own. There are three kinds of messages a goTenna can send: private one-to-one messages, private group messages, and public broadcasts (called Shouts) that anyone can receive. GliderLink exclusively send Shouts, but goTenna’s meshing feature only works for one-to-one messages at the moment. That’s why I had to implement my own meshing protocol. goTenna has said it may enable meshing for Shouts in the future.
Does GliderLink use a lot of battery?
Not really, but what can use a lot of battery is keeping the phone’s screen on all the time. Especially outdoors, where the phone automatically cranks up the screen brightness to the max. If you want to conserve your battery, I suggest you turn off the screen when you’re not looking at it.
What about the goTenna Mesh’s battery life?
The battery in the goTenna Mesh lasts quite a while. I have done 4-5 hour flights and only used 20% of the goTenna’s battery.

Can GliderLink be used for hang gliding, paragliding, or other aircraft?

I don’t see why not!

Who developed GliderLink?

Me, Ben Hirashima. I’m a professional app developer, entrepreneur, and glider pilot. I created GliderLink as a hobby and as a service to the soaring community. The app will always be free.

Will GliderLink be open sourced?

Maybe. I have to think about it. For now, it’s not a high priority.

What are your future plans for GliderLink?

There are many features I’d like to add to the app in the future. Some possibilities include:

  • Mesh networking: In addition to broadcasting your own location, the app could re-broadcast the locations of other gliders it sees, increasing the robustness and range of the network.
  • Base station mode: If on the ground, the app could broadcast live weather data to glider pilots, such as wind speed and direction at the airport. It could also send the locations of any gliders it sees to a server on the Internet, so that people at home, or your ground crew, can see where they are, sort of like glideport.aero.
  • Lift marking: Recently used thermals could be marked on the map. Color coded glider tracks could also be shown, for visualizing wave/ridge/convergence lift.
  • Mayday mode: Broadcast to anyone in range that you are in trouble, or need a retrieve.
  • Internet connectivity: If you do happen to have an Internet connection while airborne, the app can use it to share your location as well, further increasing the robustness of the system.

Is the official goTenna app required to use GliderLink?

Nope. goTenna’s own app is useful for texting friends with goTennas, like when you’re hiking in the wilderness. However, it has nothing to do with GliderLink.

What countries can GliderLink be used in?

Currently, only the USA. However, in the future it will work in any country that the goTenna Mesh works in. Those countries are:

United States, Canada, Albania, Andorra, Australia, Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Greenland, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia, Malta, Monaco, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, San Marino, Serbia, Singapore, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

Why does the goTenna Mesh disconnect occasionally?

There is a known bug in the goTenna Mesh Bluetooth firmware that causes it to crash every 30-60 minutes. This causes the goTenna to disconnect, but it usually re-connects pretty quickly. You don’t need to do anything; GliderLink will keep on working. goTenna has said it will be fixed soon. Also, make sure your firmware is up to date (see below).

How do I update the firmware on my goTenna Mesh?

You should do this when you first get your goTenna Mesh, and whenever goTenna releases a new firmware version. Download the official goTenna app. It can update the firmware for you. Make sure the goTenna battery is well charged, or plug it in while updating the firmware.