Introducing XC Tracer

The Indiegogo campaign has ended, and  XC Tracer is now available at www.xctracer.com, shipping usually within 1-2 business days. There is also more information on the new website, including the newest firmware and instructions how to update the firmware.

XC Tracer is an advanced flight instrument for paragliders, using data from an 9-DOF IMU, from a pressure sensor and from a GPS to compute the real time climb rate and altitude, avoiding the undesired time lag that conventional variometers have due to data filtering. 

Prototype of XC Tracer with 3D printed enclosure, same size as production version

Test flight with XC Tracer prototype (white box) over the Swiss Alps

Additional to that the flight path is recorded on a micro SD card as a Google Earth KML file, or later on also an IGC file will be recorded instead of the KML file.

Google KML file, created with XC Tracer, 5Hz update rate

But it get's even better. XC Tracer is Arduino compatible, and once the campaign has been successfully funded then the code will be made open source. If you want to program a better data fusion algorithm, or if you want to log different data on the SD card, or if you have another idea than to use XC Tracer for flying, then just adapt the software according to your needs, upload the code to your XC Tracer and go ahead. And last but not least is XC Tracer Swiss Made!

Rendering of XC Tracer enclosure produced using injection moulding

XC Tracer in the production version will look as in the picture above, with the dimensions 57.5 x 57.5 x 19.25mm, and a weight of only 65g.

It is planned to make XC Tracer compatible with the following apps:

• Flyskyhy (done!)
  
• FreeFlight (initiated)
  
• FreeFlightPro (initiated)
  
• theVariometer
  
• Thermgeek (done!)
  
• SkyLogger (initiated)
  
• SkyLoggerXXL (initiated)
  
• Air Navigation Pro
  
• Chillout (done!)

• Gaggle
  
• XCSoar (compatible using LXWP0 sentence)
  
• PPGpS
  
• G_Variometer
  
• FlyMe  (done!)
  
• XCTrack 
  

• LK8000 (initiated)

As a paraglider pilot and designer since more than 25 years (right now working for Gin Gliders) I was always stunned that the principle how a hang glider variometer works has not changed since I learnt to fly paragliders. Variometers measure the rate of change of altitude by detecting the change in air pressure (static pressure) as altitude changes, and a filter “smoothes” the signal in order produce a usable beeping tone that indicates the climb and sink rate. But this filtering leads to an undesired time lag. While flying in thermals the variometer may still indicate a good climb rate, but in fact this may no longer be the case, it’s just because of the time lag that the variometer still beeps, indicating a false climb rate. You can feel this when flying, there is sometimes a discrepancy between what you feel and what the variometer indicates.

My idea was then to make just a variometer that also uses the vertical acceleration in order to calculate and indicate the vertical climb rate in real time, with no time lag. A first prototype device was flown in Winter 2014, in the video made below you can see how sensitive the variometer is.

First prototype of XC Tracer in January 2014

An attitude and heading reference system AHRS consist of microelectromechanical systems (MEMS) gyroscopes, accelerometers and magnetometers on all three axes. Using all the information from these sensors it is possible to calculate the orientation of the device in space, and therefore calculate the gravity compensated vertical acceleration. A Kalman filter then estimates the altitude and climb rate, using the vertical acceleration from the AHRS and the pressure from the pressure sensor.

That worked very well, the variometer had no time lag, but then when talking with friends they had the idea to integrate a GPS, then an SD card, then a BLE module for that the fligth information can be sent to a phone or a tablet...

This is how the idea of XC Tracer was born.

What has been done so far

Technical Specifications

• 57.5 x 57.5 x 19.25mm.
• Weight is only 61g
• 14h battery autonomy
• 9-DOF IMU LSM9DSO
  
• MS5637 Pressure Sensor
  
• PA6H GPS with custom firmware, SBAS enabled at 5Hz
  
• HM-11 BLE module, iOS and Android compatible
  
• 3 led for status indication
  
• 1200mAh LiPo battery with low discharge protection circuit
  
• LiPo charger integrated
• Arduino compatible, open source and hackable
  
• ARM Cortex-M4 MK20DX256VLH7 Processor
  
• Users can develop their own code
  
• Easy solution for non-programmers to update firmware over USB
• SanDisk Ultra microSDHC 8 GB
• Micro USB cable 1m
• Swiss Made

BLE data string specification:

$XCTRC,2015,1,5,16,34,33,36,46.947508,7.453117,540.32,12.35,270.4,2.78,,,,964.93,98*67

$XCTRC,year,month,day,hour,second,centisecond,latitude,longitude,altitude,speedoverground,course,climbrate,res,res,res,rawpressure,batteryindication*checksum

A second option is to use generic GPGGA and GPRMC NMEA sentences with 1Hz, and LXWP0 or LK8EX1 sentence with 10Hz.

Since XC Tracer is open source it will be easy to output other data, you can configure the data that will be sent over BLE according to your wishes.

What you will get

For one perk you will get a fully functional and Swiss Made XC Tracer with an enclosure made by injection moulding, a micro USB cable and a micro SD card with 8GB.

Plug your XC Tracer into an USB charger or an USB plug, charge until the green LED lights up, and then go fly with you new instrument. As soon as you take off the logging of a KML file will start, recording your position and altitude with a frequency of 5Hz. And of course data will be sent over BLE to your Android or iOS device for that you have all the flight information that you need. After landing simply switch off the device, the log file will be written to the SD card before the device will actually be switched off. Once at home take out the SD card and transfer the log file to a computer, and you will see the flight on Google Earth that you recorded. 

Since XC Tracer is open source it will be easy to output other data, you can configure the data that will be sent over BLE according to your wishes.

Other ways to help

Please talk about this Indiegogo campaign and talk to your friends, make a post on Facebook, send your local paragliding club the link of the campaign. This may help to make this campaign a success.

Risks & Challenges

This is not a product from a company that produces flight instruments for hang gliders since a long time: It started as a hobby and took more than 18 months of development until the project was mature enough for the start of the Indiegogo campaign. Many hardware and software iterations have been made, many flaws have been detect and corrected. Nevertheless it might still might be possible that there are some minor bugs in the hard or the software. But the good news is that the software is open source, the users will be able to modify, adapt or fix the code to their needs. 

As always in projects there can anything happen to cause delays: production delays, parts delivery, carrier delays, holidays, technical problems etc. But I will do my best for that the perks will be delivered in time.

Liability

Use of XC Tracer is at your own risk. Koni Schafroth disclaims all responsibility for any resulting damage, injury, or expense. It is your responsibility to make sure that your activities comply with applicable laws, including copyright.