New Beginnings - Contextualising Sensor Data

Overview

Today we met during the assigned lab time to make a start on the second assignment. We started by discussing the assignment specification and clearing up a few of the details of what was required with Jacob. Our understanding of the assignment is to train an application to be able to classify 4-5 potential user/phone states based on two (or more) sensors on a phone.

This will require generating a training/testing data set. To do this we will need to write an application that can log sensor values and their associated state. We can then use this data to train our application to predict what a user’s state is based on the current readings from the sensor.

The Sensors

The first two sensors we have chosen to use to train our model is the gyroscope and the accelerometer. The accelerometer and gyroscope are both considered orientation sensors.

The accelerometer measures the amount of acceleration an object has in relation to gravity and other objects and is measured meters per second squared. In other words, the amount of force being exerted on the object - such as the force of gravity pulling at our feet. On the other hand, the gyroscope detects the current orientation of the object and the angular rotational velocity. Both sensors measure a rate of change, they just measure rate of change for different values. The device calibrates both sensors values to 0 to when they are in their default state (e.g. the phone resting flat on a table would set gyro to 0), any changes from the default state are recorded, and we can measure these changes and analyze them so we can contextualize the readings to compute user/device context. The gyroscope is measured in radians per second. The motions of the sensors can be shown using the images below:

Accelerometer

Gyroscope

For our assignment, we chose the following five states:

1) Sitting
2) Falling
3) Taking the stairs
4) Running
5) Walking

We picked these five classes because it covers a wide range of different motions in the hope that the model will be able to successfully distinguish each of the states from one another.

Next Steps
The next step is to write the code that will log the sensor values. Because we didn’t realise we had to write an application for the compass in the last milestone, it means that we need to start from scratch here.






Written by: Alex, Celine
Edited/Proof Read by: Sam