How to merge Tempo Disc sensor data into GPX files
2021-06-09
- Tempo Disc Devices
- How to turn the Tempo Disc On and Off
- Install the Tempo Plus 2 App
- Using the Tempo Disc with OruxMaps
- Using the Tempo Disc with GPXAnalyzer
- Install GPXAnalyzer
- Configure your Tempo Disc sensor
- Collect Tempo Disc and GPS data
- Upload data to your computer
- Merge the Tempo Disc data into the GPX file
Blue Maestro (https://bluemaestro.com) makes sensors that report temperature, humidity, and/or pressure to your phone over bluetooth. They can report in real-time and also log the data to their internal storage so that you can download the data at a future time.
This document focuses on the Tempo Disc 4-in-1 Bluetooth Sensor Logger because it includes an accurate pressure sensor (barometer). This data can be converted to elevation data and used to improve the elevation data in your GPX file.
The Blue Maestro Pebble sensor also includes a pressure sensor and should be able to be used in a similar manner.
To turn the Tempo Disc sensor on, press and release the purple button. You do not need to hold the button down, just press for a short time. If you look in through the vent holes the green LED will flash briefly. It will flash once if the device is turning on. It will flash 3 times of the device is already on (it remains on).
To turn the Tempo Disc sensor off, first close the Tempo Plus 2 app on your phone. If the app is connected to the device it can prevent the device from turning off. Then press and hold the purple button. Look through the vent holes and after about 6 seconds the green LED will flash. It will continue flashing until you release the button. If it only flashes once that means the device is connected to your phone or other device, and is not turning off.
Tempo Disc side view showing vent holes
In most applications people leave the Tempo Disc turned on more or less all the time. The expected battery lifetime is about 1 year. However if you are using the Tempo Disc to create log files that will be merged with the GPX file using GPXAnzalzyer, we will be shortening the sample rate to once every 10 seconds. This reduces battery life to about 1 month. Therefore I normally turn the device on only when I am using it, and turn it off at other times.
When you turn on the Tempo Disc sensor it reboots. With older firmware versions it will lose its configuration and all stored data (log files). With newer firmware versions it will remember the configuration and log files, but the timestamps on the data before rebooting are lost, so when you download the logs they will have incorrect timestamps.
You must set the sample rate after each turn-on. This will ensure that the sample rate is correct and will erase any old log files on the device (though it will not erase log files on your phone).
Install the Tempo Plus 2 app on your phone. You will use this app to configure your device, and to download log files from the device to your phone.
Download the Tempo Plus 2 app (by Blue Maestro) from the Google Play store (Android) or the App Store (iPhone). Install it as usual.
To test the app an your phone:
- Turn on your Tempo Disc sensor device.
- Enable bluetooth and location services on your phone.
- Run the Tempo Plus 2 app.
The screen will show your device.
If you do not see your device listed, make sure the device is turned on and is close by. Make sure your phone's bluetooth is turned on. You do not need to "pair" your phone with the device—the Tempo Disc broadcasts the data over bluetooth, and pairing is not necessary.
If you are using an Android phone, you can connect your Tempo Disc sensor directly to OruxMaps. OruxMaps is a mapping application for Android available in the Google Play store.
-
Make sure you have the latest version (version 8.1.8 or later) installed.
-
In Global settings, click Sensors > Tempo Disc Sensor > Tempo Disc Sensor Device Mac.
This will list all bluetooth devices it sees. Select your TD device based on its serial number.
-
In Global settings, click Sensors > GPS.
Then check Barometer for elevation and Barometer autocalibration.
Set the Barometer autocalibration method to GPS
-
Click the tracks icon (squigly line icon in top navigation drawer). Then click Sensors > Start Tempo Disc BT.
Orux maps should now use the Tempo Disc sensor for elevation.
You can configure the Dashboard and Trip Computer controls to show temperature, relative humidity, barometric pressure, and/or barometric altitude. Use the "BT" (bluetooth) versions of the controls (such as "Temperature BT") to see the values from the Tempo Disc sensor.
If you are not using OruxMaps, or you want a more accurate calibration algorithm, you can use the GPXAnalyzer program to merge barometer and temperature data collected by the Tempo Disc sensor into your GPX file. You can use a stand-alone GPS device to collect the location data and create a GPX file, or you can use any GPS application running on your phone.
The remainder of this document describes how to do this.
Install the GPXAnalyzer program on your computer.
For Windows 10, you can download an installer program from
https://github.com/dmcclimans/GPXAnalyzer/releases/latest
For Mac and Linux users, there is no pre-built installer.
If you have a reasonably recent version of Python installed are familiar with running python
programs, you can download the GPXAnalyzer.py and GPXAnalyze.py files from
https://github.com/dmcclimans/GPXAnalyzer
and run the GPXAnalyzer.py script. You will need to install several "packages" using
pip install <package-name>
The required packages are:
gpxpy
PySimpleGUI
seaborn
lxml
pytz
tzlocal
The Tempo Disc sensor defaults to logging data once an hour. That might be useful if you are tracking changes to the weather, but we will need much more frequent sampling if we want to use the pressure data to measure elevation (altitude).
The specifications for the Tempo Disc sensor say the minimum sample period is once per minute. Even this is slower than we would like. In conversation with support people at Tempo Disc, they said they had successfully tested down to 20 seconds, but that the device might not keep up with shorter sample intervals.
In my own testing I found that 10 second intervals worked fine, but that 5 second intervals failed. At 5 seconds the device would appear to work, and would produced log files that had time stamps with 5 second intervals, but by comparing with other devices it was clear that the actual sample interval was about 6 seconds. I settled on 10 second intervals as the fastest reliable sample interval.
One problem with using 10 second sample intervals is that it shortens your battery life. My testing shows that the battery lasts about 1 month of continuous logging when using 10 second intervals. To get longer battery life you can turn the device off when you are not using it.
When you turn the device off and back on, the Tempo Disc will reboot when you turn. With older firmware versions it will lose its configuration and all stored data (log files). With newer firmware versions it will remember the configuration and log files), but the timestamps on the data before rebooting are lost, so when you download the logs they will have incorrect timestamps.
To avoid problems, you must set the sample rate after each turn-on. This will ensure that the sample rate is correct and will erase any old log files.
To set the sample interval:
- Run the Tempo Plus 2 app.
- Tap the device to get to the device download screen.
- Tap the "Edit" button next to "Device settings".
- Tap the "Edit" button next to "Logging interval".
- Enter the desired sample interval (10) and tap OK.
- Wait for the app to acknowledge the change.
The next step is to take a hike, go for a bike ride, or do whatever you want to do while you collect Tempo Disc and GPS data.
- Turn on your Tempo Disc device.
- Use the Tempo Plus 2 app on your phone to configure the Tempo Disc device for 10 second sampling.
- Turn on your GPS device. This can be an app on your phone (I use Orux Maps on Android), or a separate GPS device.
- Go for a hike! (or bike ride, or whatever).
When you have finished your activity, you need to upload the date from your GPS device and your Tempo Disc device to your computer.
You should do this soon after finishing your activity. The Tempo Disc stores 6000 data points before it starts overwriting old data. If you have set your sample interval to 10 seconds, this represents 1000 minutes, or 16 hours and 40 minutes. You need to upload the data from the device to your phone before that time elapses.
-
Upload the Tempo Disc data from the device to your phone.
- Run the Tempo Plus 2 app
- Click on the device
- Click the Download button
- Wait for the download to complete
-
Transfer the Tempo Disc data from your phone to your computer
The procedure for this will vary depending on your phone, but for my phone running Android 11 it looks like this:
-
Connect your phone to your computer using a USB cable.
-
Change the USBPreferences on your phone to allow File Transfer
-
On your computer navigate to
<phone>/Internal shared storage/Android/data/com.bluemaestro.tempo_plus_2/files -
Copy the data file from your phone to your computer. The file will be named something like:
DB43763D_1613780623307_log.csv
-
-
Transfer the GPX file from your device to your computer.
The procedure for this will vary depending on what type of device you are using.
- You may need to "save" or "export" your track to save it as a GPX file. Or, this step may happen automatically depending on your device and how you have it configured.
- Connect your device to your computer.
- On your computer navigate to the gpx file and copy it to your computer.
Run the GPXAnalyzer program to merge the Tempo Disc elevation (and optionally, temperature) data into the GPX file.
The GPXAnalyzer window will look something like this:
-
Specify the GPX file from your GPS devices as the input file, and the CSV file from your Tempo Disc device as the Sensor File.
-
In most cases you should use calibration method C (Linear fit in 1 hour sections).
-
Specify an output file name suffix. This suffix will be appended to the input file name to create the output file. I usually use "_TD" as the suffix, to indicate that the data in the output GPX file has been updated with the data from the Tempo Disc sensors.