Sensors: In day-to-day life and in research

Sensors are everywhere today. A normal smartphone contains more than 10 different sensors. These not only help us go about our day-to-day life but are also becoming more and more useful for doing important research.

The most famous sensor in a smartphone is the GPS sensor. GPS is short for Global Positioning System. This system consists of 31 satellites orbiting the Earth. Each satellite is constantly sending a radio signal with information about its position and the current time. The GPS sensor in your smartphone receives different signals and detects tiny differences in the times they were sent. Four different signals are needed for the phone to estimate its location and the accuracy of the measurement, and since there are 31 satellites altogether the phone will usually pick up around 9 different signals if it is under the bare sky on a cloud-free day. In good conditions, the location can be determined with the accuracy of a single meter!

Another important sensor is the accelerometer. As the name implies, it measures acceleration. The accelerometer is a tiny box with a metal grid inside it that is attached to the walls of the box via springs. When the phone moves, the grid shifts its position, which causes tiny changes in the electromagnetic field surrounding the grid that are picked up by plates around it. Three different accelerometers can measure acceleration in the three spatial dimensions, and from this the phone can piece together its movement. If you are interested on getting to know in more detail how an accelerometer works, check out this video.

These sensors are great for when you want to find your way in Barcelona using Google Maps or know how many steps you have taken today. And they also help the researchers in BiSC to measure what is called personal exposure. Before, researchers that wanted to study personal exposure could only look at the environment surrounding the home address, which was not very precise. Nowadays, using GPS sensors and accelerometers, it is possible to know if a person has travelled the main streets with the highest particle concentrations, how many trees she has encountered in a day, and whether she used a bike or a car to get around. This technology is a massive step forward for capturing the actual day-to-day life of people and increase our understanding of environmental exposures and health.

Do you remember that during the pregnancy we asked you to carry a phone with you for a week? We are currently analyzing the information extracted thanks to the phone’s sensors in order to determine exposure to pollutants during travel, as well as physical activity, transportation methods, and access to green spaces.

This post has been written by Karl Samuelsson, postdoctoral researcher at the BiSC Project.