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Uggy payload - Data analysis with gnuplot

12 06 2014   //   Written by Yannick   //   Classified in : HAB  //  Tags : altitude, pressure, temperature, gnuplot


We previously get some data collected by Habitat server, but in this post, we are using Gnuplot to plot our data.
This is data that has been stored on the payload, not only the data sent to Habitat server during te flight.

Data sent during the flight do not contain:

  • Data for every minutes of the flight
  • Data about some sensors (like pressure)

To have my files in the same time zone as Habitat, I subtracted 1 hour with date command as bellow:

for i in `cat toto | awk '{print $1}'`; do date -d "$i 1 hour ago" | awk '{print $4}' >> tutu; done

Use of gnuplot

Gnuplot can be installed on Debian with a simple apt-get install gnuplot.

Exemple of commands used to create the graph.

gnuplot> set title "Altitude"
gnuplot> unset key
gnuplot> set xlabel 'Hour'
gnuplot> set ylabel 'Altitude'
gnuplot> set grid
gnuplot> set xdata time
gnuplot> set timefmt '%H:%M:%S'
gnuplot> set format x '%H:%M'
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w lp
gnuplot> set y2tics
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w l, 'pression_data_UTC.txt' using 1:2 w l axes x1y2
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w l, 'temperature_data_UTC.txt' using 1:3 w l axes x1y2 ,'temperature_data_UTC.txt' using 1:2 w l axes x1y2

We are lucky, the graph created is similar to previous graphs from x-f.lv

UGGY Payload data

Temperature vs altitude

2 DS18B20 sensors were used (Internal/External)

Pressure vs altitude

BMP085 was used.
It is rated as:

Pressure range: 300...1100hPa (+9000m...-500m  above sea level)

So.. I was expecting nothing below 300 hPa… but instead I get something that makes sense up to 34Km… :)

Altitude plotted is from the GPS receiver. (NOT a guess from the BMP085 from calculated pressure)