Margules Groome regularly uses up-to-date satellite imagery to assess aspects of forests. COVID-19 travel restrictions resulted in us using this technology to its fullest extent in lieu of forest site visits.
According to the United Nations Office for Outer Space Affairs,[1] there were 7 389 individual satellites in space at the end of April 2021 and that number is increasing each year.[2] The Union of Concerned Scientists, as of 1 May 2021, estimates that there were about 4 084 active satellites orbiting the Earth.[3] The implication being that there are thousands of unused satellites orbiting the Earth.
Many satellite imaging products and services are available for navigation services, weather services and environmental monitoring. Our focus is accessing data from satellites that collect visible to infrared frequencies.
Some satellite imaging products can be accessed for free and include medium-resolution imaging satellites products. Some government/publicly owned satellites have freely accessible imagery, such as the NASA Landsat satellite series, of which two are currently active and an additional one is due to be launched in September 2021. Landsat imagery is prevalently used in land use monitoring due to its relatively high resolution, high number and range of bandwidths collected, free access, and regular image collection. The Terra satellite, also run by NASA, carries five instruments that collect data and can be used for climate analysis (tracking clouds, temperature, radiation, aerosols, and pollution among other things). The Sentinel series satellites run by the European Union’s Earth Observation Programme are also available for free and collect regular imagery of Earth in thirteen spectral bands. The amazing aspect to the Landsat and Sentinel series imagery is the sheer number of images available from archive and the resolution of the true colour bands available: 15 m (with some post-processing) and 10 m resolution respectively.
There are many commercially available satellite imagery providers and below is a table of some very high-resolution imagery sensors with a link to a provider.
| Satellite/Satellite Series | Resolution | Link to Available Imagery |
| SPOT | 1.5 m | https://apollomapping.com/spot-satellite-imagery |
| GeoEye | 0.41–1.64 m | https://apollomapping.com/geoeye-1-satellite-imagery |
| OrbView | 1–4 m | https://earthexplorer.usgs.gov/ |
| WorldView | 0.31–1.8 m | https://apollomapping.com/worldview-4-satellite-imagery |
| Pléiades | 0.5–2 m | https://apollomapping.com/pleiades-1-satellite-imagery |
| SkySat | 0.5–2 m | https://apollomapping.com/skysat-satellite-imagery |
| SuperView | 0.5–2 m | https://apollomapping.com/superview-1-satellite-imagery |
A standout satellite is WorldView-3 from the WorldView satellite series which collects imagery as good as 0.31 m resolution, the world’s highest resolution commercial imaging service. An example of the imagery available through the sensors on the WorldView-3 satellite can be seen here.
Satellites are becoming more diverse, as an example, the world’s first wooden satellite will be launched this year. This is a small satellite measuring 10 cm x 10 cm x 10 cm and uses a special coating on the plywood to make it robust enough to withstand space.[4] There will be several made in Finland, to be launched in New Zealand.
We can expect the number of satellites and products on offer to continue to increase. As these develop so will our abilities to use these products to better measure, monitor, and manage our forests. For more information contact Margules Groome.
[1] https://www.unoosa.org/oosa/osoindex/index.jspx?lf_id=
[2] https://www.geospatialworld.net/blogs/how-many-satellites-are-orbiting-the-earth-in-2021/