Journalists considering whether to include sensor data in their own reporting may want to evaluate their story, their goals, and the potential data they need. This section is intended as an aid for readers to understand the differences between sensors and the range of characteristics they can have—thereby helping them match the best tools to their needs. It should also be useful for reporters who are looking for data; this set of continuums may help them broaden the range of places they go looking for sources. The final use might be for readers who want to examine other people’s work with sensors, to help them analyze whether the purported conclusions can be supported by the underlying data production process. The characteristics labeled below are only the ones that seem most important and commonly applicable. It is not useful for us to work through every potential characteristic of a sensor system. By way of example, most journalists will want to consider their sensors’ degree of accuracy and precision, a few will need to consider power use, and almost none will need to consider how old their sensors are. These characteristics may be a function of an individual sensor, or a whole sensor system.
Measurement Qualities These characteristics primarily concern the data that a sensor produces.1Sensitivity to Target Phenomenon Simply, the relationship between the amount of phenomenon the sensor is intended to detect and the amount of the sensor’s output. Sensitivity to Interference The degree to which a sensor’s detection of the target phenomenon is influenced by other factors. In most cases, users will want their sensor systems to be insensitive to interference. Precision The degree to which a sensor can produce a data that is exact. Range The degree to which a sensor can detect very little of the phenomenon, up to a lot. For example, some accelerometers may have a range of only -2 times gravity, to +2 times gravity, whereas others have a range of -4/+4 or greater. Linearity The degree to which a sensor’s output is consistent across the whole of its range. A temperature sensor has a high degree of linearity if it records temperature to within 1 degree at -30 and +30 (and everywhere in between).
Resolution This quality has two important facets: spatial and temporal. A sensor system with high temporal resolution will produce data with lots of values in a given time period. A sensor system with high spatial resolution will produce data with lots of values for a given area. Operational Qualities These characteristics may act upon the previous set of qualities, but may also affect how practical it is for journalists to use the sensors, or access the sensors’ data. We include these qualities here because of their relevance to our case studies. Maturity A sensor system may be mature if it has been widely used, thoroughly tested, and is not undergoing rapid functionality development. Sensor systems that are immature are less likely to be suitable for applications where users need reproducibility and reliability. A recently designed prototype water quality sensor, for example, is unlikely to produce data that can withstand challenges from stakeholders, or be used in courts to prove water is unsafe. Ownership Sensor systems may be owned and/or controlled by individuals, governments, or private entities. Ownership may be relevant because it affects whether journalists can access the data, where sensors may be placed or moved, and which sets of laws govern the information the sensor is permitted to collect. It will be difficult for journalists to access data from sensors owned and operated by private companies. The operators of governmentowned sensors may, for example, need to consider the United States Constitution’s Fourth Amendment restrictions on unreasonable searches.
Autonomy Sensor systems can require various levels of proximate, immediate control to operate. A handheld x-ray soil contaminant sensor is under close control, whereas a camera mounted on a drone flying between preset waypoints is under less immediate control. Operating Distance Various sensors are designed to work at different distances from their subject. A Fitbit activity monitor only works if it is directly touching the subject, whereas a satellite collects information at a vast distance (especially if it is turned away from the Earth).