Measuring whole cities involves thinking about deploying sensors and being clever about how to measure so that the costs are still manageable.
As the sensor device has become more and more stable, we started to worry about improving methods of deployment. Last year, we had already come up with a method of mounting the device on the rooftop of a car, as can be seen in the photo. This mount had been tested several times and worked well.
In cases, such as measuring smaller areas, it is easier to walk around with the device, so we devised the backpack rig we can easily use to walk around. The backpack even fits an extra battery pack, and even fits an umbrella still so we could walk out in the rain. This also allows anyone interested to go for a measuring walk.
Yesterday, we used our new walking rig and had a stroll around the Kupittaa area. The initial values were very high (purple), which either reflects the truth as there was plenty of traffic, but is most likely that the sensor is just warming up. This is not surprising as the sensor documentation indicated that it might, and with further testing we will be able to determine the proper warm-up time. Using those findings we can ensure that such incorrect values are discarded as necessary.
In order words, we have moved on to being concerned about the actual sensor values more than the device or the infrastructure. It is soon time to measure a real location, such as a building or a neighbourhood.