DataAnalysisForRobotics

Data Analysis for Robotics Projects with ROS

Data analysis for GNSS systems

Tools to plot and verify the data from a GNSS system, checking RTK status and random walk.

Stationary test

Check the deviation of a GNSS system.

What it does

• It will draw one circle within the specified range, defined by the user as a kind of random walk limit

• It will draw an ellipse containing 95% of the points to check it's distribution while stationary.

How to run it

• Collect a /fix rosbag.

• Rename it to run_<run_number>.bag (e.g run_42.bag)

• Convert the bag into a csv file with bag_to_csv.py From the repository folder, run:

  python scripts/bag_to_csv.py --folder /path/to/bag/folder --num_bags 1

  Arguments:

  --folder : Path to the folder containing the .bag files.

  --num_bags : Number of bag files to process. Practicaly, it should always be one, as there is no reasson to merge more than one bag, unless it was a interrupted stationary test or something similar

• Run the script to generate the stationary plot, with the csv generated as input

  python <plot_gps_from_csv.py path> --csv <.csv file path> --max-distance <distance_threshold>

  Arguments:

  --csv Path of the csv file(usually inside the run_<run_number> folder)

  --max-distance Distance of the max distance threshold(Circle)

  e.g.

  python3 scripts/plot_gps_from_csv.py --csv run_0/ublox-fix.csv --max-distance 0.2
  

Moving (Lap) Test

Segment a trajectory into laps and plot continuous, colored paths for each run.

What it does

• Scans every run_* folder under a user‑provided root directory.
• For each run_X, reads all *-fix.csv files (e.g. ublox_F9P-fix.csv, blabla-fix.csv).
• Segments each file’s latitude/longitude data into laps based on:
  • distance threshold (meters to close a lap)
  • minimum duration (seconds before considering a lap closed)
• Generates:
  1. Per‑sensor plots: run_X_<sensor>_continuous_laps.png (one PNG per sensor per run).
  2. Combined plot: run_X_combined_continuous_laps.png, overlaying all sensors’ laps.

All plots are saved in the plots/ folder under the specified root.

How to run it

From the GNSS/scripts/ directory:

python plot_gps_laps_from_csv.py \
  --data_dir /path/to/GNSS \
  [--run_distance_threshold 5.0] \
  [--min_run_duration 30.0]

Arguments

• --data_dir : Root folder containing run_* subdirectories (required).
• --run_distance_threshold: Meters to close a lap (default: 5.0).
• --min_run_duration : Min lap duration in seconds (default: 30.0).

Example

python plot_gps_laps_from_csv.py \
  --data_dir ~/Documents/VAL/GNSS/git/DataAnalysisForRobotics \
  --run_distance_threshold 3.0 \
  --min_run_duration 20.0

After running, check the plots/ folder at the project root for all generated PNGs.