Earth observation satellites can give us a wealth of information about what’s going on in property and urban development, often well before the fastest-produced economic reports.

Space technology in the form of global positioning systems (GPS) is well entrenched as part of modern prop tech, but this article looks at a different space-based technology called Earth observation (EO), and how it can play a part in all stages of the land development cycle. EO is principally concerned with satellites orbiting the Earth, taking digital images continually. We’re very familiar with this imagery on Google Earth, or on the weather forecast; however, these aren’t just pretty pictures but pieces of geospatial information with a wealth of applications. Much of this information is free, with an online supply of the very latest images of anywhere on the globe available from NASA and the European Space Agency (often within just hours of the satellite going overhead). There are also private sector enterprises with their own fleets (or “constellations”) of satellites providing multiple high-resolution images daily (sub-metre resolution in many cases), which can be acquired with nothing more than a credit card. There are now private sector space companies that can provide high-resolution video, from space, for anywhere in the world, on demand. The sensors on these satellites can take regular imagery, but also see part of the electromagnetic spectrum beyond the visible. They can see through clouds with microwave signals, measure height or detect gasses in the atmosphere. They can image an entire hemisphere in one go or detect movement down to millimetres. But how can they and how do they fit in with the property business?

TAKEN AT THE FLOOD
Flood duration from the Sentinel-1 satellite.

Land acquisitions and management
If you want to know the land use history of a parcel of land, then satellites can provide the answers. EO satellites have been observing the planet since the 1970s and, utilising newly available archives of NASA Landsat data, Teagasc has developed software that can give you a full 40-year land use history of any agricultural parcel. This sort of information isn’t available from other means and can provide an evidence base as part of any life cycle assessment or any sustainable development certification (e.g., ISO 21929-1). Having this sort of knowledge of a parcel of land and its neighbours can also be an important part of a due diligence process for investors. Teagasc research into EO of land is also looking at assessing its current status. We now have methods to assess drainage on land via satellite, and to track the immediate and long-term effects of flooding using radar satellites that can see through cloud. Combining imaging satellites with radar we can assess current growing and management conditions on farm land and forested land. Our machine learning models can estimate crop and grass yields, and detect change and damage in forestry. This can give landowners who are not on site knowledge about performance, abandonment or land security (good for long-term monitoring of undeveloped sites). Crucially, EO satellites can see anywhere in the world and look for change automatically, perhaps making the management of overseas portfolios easier, especially large estates, parklands, golf courses, etc. It’s this ability to see anywhere that gives EO tech such a strong potential in property management. By combining historical knowledge and current practice, we can estimate carbon stocks both above and below ground, and estimate current carbon sequestration using our EO data and models. It’s likely that knowledge of carbon stock changes due to land use change will become part of any sustainability indicator or strategic environmental assessment (SEA) process in the future.

 

Shedding light on economic development
Where are the up and coming areas? Can EO spot trends? Across much of the world, where official statistics might be lacking, EO is used to see the impact of economic activity at an early stage. One neat trick is night time mapping, where satellites measure the brightness of towns and cities at night (from street lights, houses and traffic). Lots of studies show that an increase in brightness levels is directly linked to economic activity and shows up long before any evidence in official economic statistics. In more developed economies, high-resolution satellite imagery can capture early changes in economic growth in a locale by being able to measure traffic volumes, or count cars in out-of-town shopping centre carparks. Imagery can spot the early impact of gentrification by automatically counting trees in a neighbourhood or the greening of common spaces, by exploiting near infra-red (NIR) imagery, which is very sensitive to vegetation. As EO can see anywhere, it’s been used to look at changes in the make-up of gardens in a neighbourhood or automatically count the small improvements like attic conversions and extensions that don’t need planning permission using a technique known as image segmentation. All of this information can be combined with conventional survey data and demographics in a geographic information system (GIS) to predict likely areas of gentrification. Or, using a method known as agent-based modelling, predictions can be made about land use change in the future in both agricultural and peri-urban areas.

FOUR GREEN FIELDS
Monitoring grass via near infra-red (NIR) imagery.

Watching the buildings
EO can be an excellent tool for monitoring building developments. Using photogrammetric techniques, 3D models can be constructed from satellite images, but a more interesting technique can be used to monitor building integrity. Radar satellites build up a picture of the Earth by measuring the return of a microwave signal they generate. As well as the intensity of the returned signal, the length of the path of return can be used in a process called interferometry to measure very small changes in height; meaning the satellite can detect subsidence in a neighbourhood or individual building down to millimetres. EO can provide information for whole building monitoring, especially in high-rise urban areas where drones can’t be used. EO technology, whether freely acquired or with a private partner, can provide insights that aren’t otherwise available. It gives access globally and at any time. The data and information it provides can potentially add value at all stages of the property devolvement cycle for all partners: surveyors, owners or investors. This article has touched on only a tiny fraction of the vast capabilities of the hundreds of EO satellites currently acquiring data.

 

Sources of EO data:
www.apps.sentinel-hub.com/eo-browser
www.planet.com/explorer

 


 

Stuart Green

Senior Research Officer, Teagasc