The beauty of Earth Observation: Dr Fleur Visser
Ideas on how to use Earth observation
Since 1972 the Landsat programme satellites have been collecting image information. Landsat data is collected at regular intervals and is produced every two weeks. There is a long history of data which allows analysts to look at detailed changes over time on the surface of the Earth. Data can be used in many ways. For example, data from Landsat satellites is used by the USGS (United States Geological Survey) for Earth Explorer.
Alternatively, Aster data produces stereo imagery. Just like stereo aerial photos from two different angles, these satellites allow you to produce a digital aerial model to work out things like the size and thickness of a glacier.
Example imagery
Hielo Patagónico Sur 12 (HPS-12) is believed to be the fastest-thinning glacier in the world. By using light beyond the visible spectrum, the false colour image clearly shows different surface types. There are multiple images in a ‘slider tool’ on the NASA website on the southern Patagonia ice field.
False colour images of changes to the Mont Blanc massif are also available to view from NASA.
Below you can see Aster image data of the Tasman glacier in New Zealand. It has retreated 180 metres every year since 1990, when the first image was acquired by the Landsat 4 satellite. It is a flash colour image showing frozen snow or ice in white and vegetation in red.
The next Earth observation image shows New Delhi in India. Using a combination of visible and short-wave infrared light, the image was recorded as Landsat image data. Due to this recorded Landsat data light, it is easier to distinguish urban areas.
Data was acquired and collected between 1989 and 2018 to show the urban growth of New Delhi, India. Images like this have been invaluable in our understanding of spatial patterns and processes such as urban growth, urban sprawl, counter-urbanisation and the identification of different land use.
If you are looking for a good place to start with Earth observation data try the Where to get data for NASA Landsat data. From here you can opt for ‘rapid online viewing’ of satellite imagery or you can download data sets. If you are unsure on how to proceed read the How to use data webpage.
The previous image of Shanghai in China is produced by the European Space Agency (ESA). It shows the urban change in 5-year intervals from 1985 to 2015.
It is part of the WSF-Evolution global settlement map, which is created from six million Landsat satellite images. You can view and download this Shanghai data set from the ESA
This picture shows how precise Earth observation can be. In the image near infrared light has been used to enhance the visibility of plant leaf and stem shapes. Using Object Based Image Analysis (OBIA) classification, this enables species level classification of submerged aquatic plants – fieldwork which can all be done remotely.
You can use Landsat data in your school, scroll to the end of this page for a teaching idea to get started with using Earth observation.
In the above image the strong reduction of near infrared light when it passes through water also enables the mapping of submerged topography, including vegetation.
A drone orthoimage means a picture has been geometrically corrected, otherwise known as being ‘orthorectified’. It is still an accurate map image but has been georeferenced to adjust for drone camera tilt, lens distortion and topographic relief.
Extension work
Could you measure the amount green space using Landsat data in your school? (Landsat picks up red, green and blue). You could make this more interesting by doing the exercise over time. What has changed?