  While the radio spectrum allocation is well regulated, there is little
knowledge about its actual utilization over time and space. This limitation
hinders taking effective actions in various applications including cognitive
radios, electrosmog monitoring, and law enforcement. We introduce Electrosense,
an initiative that seeks a more efficient, safe and reliable monitoring of the
electromagnetic space by improving the accessibility of spectrum data for the
general public. A collaborative spectrum monitoring network is designed that
monitors the spectrum at large scale with low-cost spectrum sensing nodes. The
large set of data is stored and processed in a big data architecture and
provided back to the community with an open spectrum data as a service model,
that allows users to build diverse and novel applications with different
requirements. We illustrate useful usage scenarios of the Electrosense data.
