What it shows
Delivery vans, school buses and trekkers need a record of where they went. A battery-powered logger with a GPS module stores time, position and speed on an SD card, and a Python script plots the track on a map and finds distance and average speed. The project tests accuracy against a phone and a known surveyed route.
The science
GPS receivers calculate position from the arrival times of signals from at least four satellites. The module outputs NMEA sentences such as $GPRMC with latitude, longitude, speed and time. The Haversine formula gives distance between two latitude and longitude points on a sphere. Accuracy is a few metres in the open and worse near buildings and trees because of reflections.
Materials
Cost: under Rs 5,000. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- An Arduino Nano or ESP32
- A NEO-6M GPS module with antenna
- A microSD card module and a 4 GB card
- A 3.7 V Li-ion cell with a charger module and a 5 V boost converter, or a power bank
- A small plastic box
- A laptop with Python, folium or Leaflet
- A 400 m stadium track or a measured school boundary path
Safety
For this project: Handle Li-ion cells only with a proper charger module and protection board, keep the cell inside its holder in the box and never loose in a bag, and never puncture or short it. Never charge it unattended; an adult must supervise charging. Do not track people without their consent.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
12 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Connect the GPS to the microcontroller serial port and print raw NMEA to check that a fix is obtained outdoors, which can take a minute or two.
Install the TinyGPS++ library and print latitude, longitude, speed, satellites and HDOP.
Wire the SD module over SPI and test that a file can be created and written.
Write the logger sketch to save a CSV line every 2 seconds only when the fix is valid.
Add a button and an LED: press to start or stop a trip file and blink to show logging.
Power it from the battery pack and test the run time for a two-hour walk.
Walk a 400 m track or a measured loop three times carrying the logger and a phone running a GPS app.
Write a Python script that reads the CSV, computes the distance with Haversine and the average and maximum speed.
Plot the track on an OpenStreetMap-based map using folium and save it as an HTML file.
Compare the logged distance with the true loop length, and the logger track with the phone track.
Test under tree cover and between buildings and note the HDOP and the error.
Write the report with accuracy results, causes of error and ideas for fleet tracking.
What you should see
The map shows a clear route that follows the path within about 3 to 10 metres in the open. Distance is within a few percent of the true length, and the error is much larger near tall buildings.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01Why are four satellites needed?
Three unknowns of position plus one for the receiver clock error.
02What is HDOP?
Horizontal dilution of precision: a lower number means better satellite geometry and a more accurate fix.
03What is an NMEA sentence?
A standard text message from the GPS containing time, position, speed and other data.
04Why does the signal get worse near tall buildings?
Signals reflect and arrive by several paths, which gives errors, and buildings block part of the sky.
Take it further
Send the position every minute through an ESP32 over Wi-Fi to a web page that shows the live location in a campus.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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