Remote sensing

Remote sensing is the use of sensors to extend our human senses in observing and recording objects or events that are far away (remote) from us. The sensors are not in direct contact with what is being observed, so the observations do not disturb the object or area of interest.

Remote sensing can be ground-based – like weather stations or seismometers that detect movements under the Earth. Sensing can also be airborne – with sensors attached to airplanes or drones. The third method of remote sensing is with satellites.

Advantages of using satellites to collect data

Scientific research often involves measuring something – changes in animal populations or sea ice thickness for example. Although the work is exciting, travel to these places is often expensive, sometimes dangerous and is one snapshot in time. High-resolution remote sensing using a satellite in low Earth orbit is able to make these sorts of measurements quickly, precisely and often.

Satellites circle the Earth several times a day, and they have wide fields of view. Sensors on the satellites are becoming increasingly sophisticated. MethaneSAT is able to detect differences in methane levels as small as 2 parts per billion. NASA’s PACE satellite can take full-colour images with a 1 km pixel size from anywhere in the world. Being able to collect so much amazing data is a huge advancement, but it’s only numbers and pictures without careful interpretation by humans.

The journey of the data

Satellite sensors collect data as they fly over the Earth. The data is held by the satellite until it passes over a ground station – a special satellite dish antenna that points up towards a portion of the sky. Ground stations receive the communication downlink from the satellite, downloading enormous amounts of information in a few minutes. The data is then sent to processing centres where skilful people use special software packages to process the data and make it usable.

Xerra – using Earth observation and remote sensing

The Xerra Earth Observation Institute is based in Alexandra, Central Otago. The team of remote-sensing and data scientists, software engineers and communications experts helps people obtain and make sense of satellite data. Xerra has access to multiple satellites from both commercial satellite operators and agencies like NASA and the European Space Agency, which share their data and imagery free of charge.

Xerra processes and interprets satellite imagery to monitor phenomena like algal blooms in fresh and coastal waterways or the fire-fronts of bushfires, which are hidden under clouds of smoke. This type of monitoring improves our abilities to alert and protect people and natural environments.

Everything we do at Xerra comes back to kaitiakitanga, or guardianship of our land, water and sky – from the suppliers and partners with whom we choose to work, to the projects to which we commit ourselves.

Xerra Earth Observation Institute

Xerra has developed ©Starboard Maritime Intelligence, a software platform that helps countries monitor their national waters for activities like illegal fishing and dark vessels. Dark vessels either do not have automatic identification systems or they switch off their location-transmitting devices to avoid being detected.

Starboard also monitors biosecurity risks, helping to protect Aotearoa and other countries from pests that arrive via international shipping. The satellite data shows where ships and cargo have been, and real-time tracking information allows border security teams to prioritise ships for inspection.