Measurements by thousands of citizen scientists in the Netherlands using their smartphones and the iSPEX add-on are delivering accurate data on fine air particles in the atmosphere that add valuable information to professional measurements. The scientific article that presents these first results of the iSPEX project is being published today in Geophysical Research Letters.
iSPEX is a
new atmospheric measurement method in the form of a low-cost add-on
for smartphone cameras. The iSPEX-app instructs participants to
scan the blue sky while the phone’s built-in camera takes pictures
through the iSPEX add-on.
The photos record both the spectrum and the linear polarization
[2,3] of the sunlight that is scattered by suspended fine air
particles, and thus contain information about the properties of
these particles. While such properties are difficult to measure,
much better knowledge on atmospheric particles is needed to
understand their effects on health, climate and air traffic.
Thousands of participants performed iSPEX
measurements throughout the Netherlands on three cloud-free days in
2013. This large-scale citizen science experiment allowed the
iSPEX team to
verify the reliability of this new measurement method.
Maps of fine air particles
After a rigorous quality assessment of each submitted data
point, measurements recorded in specific areas within a limited
amount of time are averaged to obtain sufficient accuracy.
Subsequently the data are converted to Aerosol Optical Thickness
(AOT), which is a standardized quantity related to the total amount
of atmospheric particles. The iSPEX
AOT data match
comparable data from satellites and the AERONET ground station at
Cabauw, the Netherlands. In areas with sufficiently high
measurement densities, the iSPEX maps
can even discern smaller details than satellite data.
Citizen science network
The great strength of iSPEX is the
measurement philosophy: the establishment of a citizen science
network of thousands of enthusiastic volunteers who actively carry
out outdoor measurements. In this way, valuable information can be
collected about fine air particles on locations and/or at times
that are not covered by professional equipment. Currently is being
investigated to what extent more information can be extracted about
atmospheric particles from the iSPEX data,
as for example their sizes and compositions. Also more measurement
days will be organised.
With the help of a grant that supports public activities in Europe
during the International Year of Light 2015, the iSPEX team is
now preparing for the international expansion of the project. This
expansion provides opportunities for national and international
parties to join the project. The final goal is to establish a
global network of citizen scientists who all contribute
measurements to study the sources and societal effects of polluting
atmospheric particles.
Strategic Programme RIVM (SPR (Strategic Programme RIVM))
The iSPEX project provides insight into the possibilities of gathering large amounts of research information with the help of involved citizens at a low cost. RIVM expects many more of these types of citizens’ initiatives to take place in the future. RIVM has the in-house knowledge to support citizen science by calibrating, compiling and interpreting the data, so that the data becomes more valuable for everyone. RIVM’s contribution to the iSPEX project is part of our Strategic Programme RIVM (SPR), which is directed to responding to key future issues and comprises many innovative projects.