All techie stuff here
Hi. I'm a sailplane pilot that has built an Android app that's mostly aimed at sailplane pilots, but may be of interest to hang glider pilots as well. I hope it's ok if I post about it here. I'll copy and paste something I posted on a sailplane forum:

The app shows your location and the location of nearby gliders on a moving map. You can see the other gliders' callsign, relative altitude, heading, and vertical speed. That's about it right now; it's very simple. The value of this app is that it allows you to quickly see where nearby gliders are, and whether they're in lift or sink. No more confusion on the radio trying to communicate to others where you are. With this app, all it takes is a glance. This enables team soaring, and increases safety by helping you be aware of where other gliders are. It could also be useful for lead/follow cross-country mentoring.

The app is free, and always will be. I developed it as a hobby and as a service to the soaring community. The app is for Android 4.3 and above, and requires Bluetooth LE (low energy, aka 4.0). I may make an iOS verison if there is enough interest. However, a used Android phone can be had for a song these days, if you don't want to wait.

Here's a screenshot:


One unique thing about this app is that it doesn't require a cellular or Internet connection to share your location with others. Instead, it 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.

This is what a goTenna Mesh looks like:


You mount the goTenna Mesh in your cockpit, in a location where it will have line-of-sight to other gliders. I have mine velcroed to the underside of my canopy, but it also works well if you tape it to the end of your microphone boom where it can "see" out through the canopy. Here's what it looks like on the underside of my canopy:


In my testing, the maximum range of the goTenna Mesh is around 41.2nm (76.3km). However, the reception is not reliable at that range. In practice, you can get fairly reliable reception within about 10nm (18.5km), which is plenty. The app shows gliders in green if you've received a position update from them recently. If the app hasn't received a signal from them in a while, the glider will be shown in orange, then red if it's been a long time.

The cost of the goTenna Mesh is quite reasonable. They sell for about $72-90 each, depending on how many you buy at once. 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 nice way to say thanks for the app, but you don't have to use it if you don't want to.

The app can be downloaded right now from Google Play:

https://play.google.com/store/apps/deta ... gliderlink

The app will walk you through some setup, which involves requesting permissions, downloading a map for offline use, and entering your callsign in the settings. Downloading the map ahead of time ensures that it will be available while airborne, where you may not get cellular reception. Make sure the phone is on WiFi when you're downloading the map. It can use a lot of data if you're on a cellular connection. The larger the map area you select, the more data/storage will be used. Once setup, tap the little switch button in the corner of the screen to connect to the goTenna Mesh(make sure it's on) and start sending/receiving data. There is also a demo mode, accessible from the menu, that allows you to see a demonstration of what it looks like when you're flying with other GliderLink users.

There are many more features I'd like to add to this 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 the FBO, 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.

I, and a few other pilots, have been testing the app around Hollister, California, and find that it comes in handy. I hope you do too, and I look forward to hearing what you think!

I have a website set up for GliderLink, but I haven't had a chance to put anything on it yet. You can check it later for more info: https://glider.link


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