Land subsidence on the radar

Poland has a strong tradition of coal mining and coal-fired power. Coal was the basis of the country’s industrialization, and today coal-fired power still accounts for over 80 % of total electricity generation.

Exploitable hard coal reserves are located in Upper- Lower Silesia, and in the Lublin basin in the east of Poland, with the Upper Silesian coalfield accounting for 78.9% of the total.

Despite their significance for the economy of Poland, mines in many cases have a negative impact on their neighborhood. One of the effects of mining is land deformation, manifested by the occurrence of e.g. subsidence basins. The problem of mining damage occurs not only during the mining period but also many years after the mine has ceased operation.

Geological disasters, including ground deformation, fractures, and collapse, are serious problems in coal mining regions, which have threatened the sustainable development of the local industry – the safety of residents.


“Everywhere you look on Earth, you see something new”
says Paul Rosen, an InSAR pioneer at NASA’s Jet Propulsion Laboratory (JPL).

Over the past 5 years, we have managed to analyze the subsidence of land caused by coal mining in the area of ​​more than 3 000 km2  in 54 municipalities in south-eastern Poland.

Our analyzes using SAR images from commercial and public satellites identified not only damage to homes, but also roads, tracks, power lines, gas pipelines, bridges, and many, many more. Owners of private properties and undeveloped plots of land – where subsidence prevents their agricultural use and threatens the stability of buildings – were also affected. The value of the subsidence of the basin in some communes it even exceeds one meter per year, reaching values of even several meters over 10 years. Therefore, post-mining subsidence causes unimaginable economic losses and poses a threat to health.

 


An innovative answer to the problem

To identify the above-mentioned problems and find a solution to them, SATIM, using its many years of experience in working with SAR imagery, has developed the OsiadanieTerenu.pl online portal. The mechanism of operation of the application is based on the use of satellite radar imagery, and then semi-automatically processed by analysts and transformed into a graphic form.

 

As a result, modern and technologically advanced images presenting identified changes on the ground surface are legible and presented on the portal in an accessible way – in the form of a map with ranges and values of subsidence occurrence. The OsiadanieTerenu.pl application facilitates the user’s control over areas degraded by mining activities and automatically generates reports containing quarterly subsidence values in centimeters. Moreover, OsiadanieTerenu.pl includes the possibility to review archival data and the function of automatic alert in case of detecting new vertical ground movement.

Landslide monitoring

Another product developed at SATIM based on radar imaging is a monitoring service to support different phases of landslide risk management. The service combines existing, established elements as landslide velocity maps derived from stacks of satellite SAR data using Persistent Scatterer Interferometry with completely new monitoring elements, as urgently required during crisis situations. The resulting products are reports on the status of landslide areas located within the boundaries of the district or detailed reports for selected landslides containing: basic geological information on the studied area including location, applied method of data processing, map with survey points, a graph showing displacements of selected PSI points in time.

OsiadanieTerenu.pl

Continual monitoring of ground deformation and landslide is important for early detection, mechanism understanding, countermeasure implementation, and deformation prediction. Detecting the features and identifying the potential risk is important for decision-makers to prevent geological disasters and for residents, too. It is vital to monitor possibly affected areas with nearly real-time up-to-date surveillance because occurring effects may entail lasting changes and influences on the environment.

Synthetic Aperture Radar (SAR) interferometry which is an advanced detection and monitoring technology slow ground movements, and currently is the most accurate and modern of all available methods. Together with our online portal www.osiadanieterenu.pl , it is an excellent source of information for all interested entities.

No other technology researching the land subsidence could produce such a comprehensive survey. Now we can measure centimeter changes across a swath hundreds of kilometers wide in a short time and with great efficiency.

Stopping climate change with earth observation

Recently, the Intergovernmental Panel on Climate Change (IPCC) published their Sixth Assessment on Climate Change, in which they present us with some rather grave news. Climate change is here, and it’s here to stay!
How we react now will determine the direction that we will progress towards, collectively, as a society. Some of the topics covered in this report, which we really should start focusing on, are: 

The five points mentioned are, probably, the most important aspects of climate change that we should consider. There are different ways to try to combat, stop, or slow down climate change. But, a tool for doing this that is not mentioned nearly enough is Earth Observation (EO). Geospatial imaging and EO are ideally fit for helping the fight against climate change because of the complementary data that they provide, the ability to see gradual changes accurately and over a long term scale (such as melting ice & glaciers), or even simply natural resource management.

 

                                                                              Credit: Pexels Markus Spiske


What is Earth Observation?

Well, the name itself is rather intuitive, if you ask me. EO is the process of observing the earth from above with the help of sensors or cameras. They are generally attached to a satellite or other flying/floating/freefalling object. So, pretty much anything that is up and over your head, far up in the sky, that has a camera or sensor attached to it, is an EO apparatus. But, to keep this simple, let’s stick to the idea of EO satellites. 

There are really two main types of EO satellites: Synthetic Aperture Radar (SAR) and Optical. An optical satellite is a traditional satellite that produces, a regular image of the earth from space, like this.

 

                                                 An optical image in 3 different conditions

 

The problem with Optical satellite imagery is that it can only be utilized approximately 25% of the time. There are many factors that contribute to the ineffectiveness of Optical satellite imagery. They have limitations. Cloud cover or darkness can render these standard images incomplete or useless, leaving blindspots when monitoring.

Now, since we have the easy part out of the way, here is a SAR satellite image. Radar satellites actively send their own radio waves towards their target and then measure what is reflected. It enables them to cover large areas in a very short time. The instrument does not require sunlight. It can be used to image areas during the night and the day, and in all weather conditions. But SAR image processing is not easy and extremely difficult to interpret.

 

  A SAR image in 3 different conditions, showing how SAR can be utilized 100% of the time


Different EO satellites are usually launched in constellations. A well-known constellation is the European Union’s Sentinel Constellation, of which there are 6 (Sentinel 1 through Sentinel 6). Each constellation is based on two satellites that fulfill the revisit and coverage requirements, which provide robust datasets for the Copernicus Services
. The reason why the Sentinels are so popular is because the data that they create is free, and, let’s be honest – who doesn’t love free data? Moreover, Each mission focuses on a different aspect of Earth observation; Atmospheric, Oceanic, and Land monitoring, and the data is of use in many applications.

How can EO be used to help with the impact of climate change?

Now that you know about the satellites and Sentinels missions, let’s step back a bit and dive deeper into how EO can be used to help with or fight the impact that climate change can, and will, have on the world and global society. An increase of the global surface temperature can have many negative implications for the world. We are currently experiencing some of the early warning signs of an increased global surface temperature. There are droughts, wildfires, increased rainstorms, and, as a result, increased flooding. 

To fight or counteract the effects of climate change, satellite data can and even need to be used. Satellite data provides authoritative information about more than half of the 50 crucial climate change variables.

Satellite measurements of Earth’s temperature, greenhouse gas emissions, sea levels, atmospheric gases, dwindling ice, monitoring IUU fishing, ocean pollution, and forest cover, etc, are essential for improving the understanding of climate change and predicting the future of the Earth.

Photo: Global concentrations of atmospheric methane produced by ESA CCI. It is from satellite data provide important information about the distribution of sources and sinks of this powerful greenhouse gas. Source: ESA.


And so for example t
he Sentinel-3 mission, which is mainly for applications for the ocean and coastal monitoring, numerical weather and ocean prediction, sea-level change and sea-surface topography monitoring, ocean primary production estimation and land-cover change mapping, and the Sentinel-4 mission, which is to monitor key air quality trace gases and aerosols over Europe.

The above-mentioned missions plus innovations such as the miniaturization of satellites, AI, ML, and high-speed data transfer have made satellites an integral part of the climate change mission. Earth Observation data is our “eye in the sky”.  Without these inputs, decision-makers, governmental leaders, and scientists won’t be able to understand, analyze and predict the impact of climate change, and formulate effective strategies.

Within the next year, many new satellite missions will be launched (e.g. UMBRA) with enhanced image resolution and better temporal resolutions. So let’s make SAR easy and help with or fight the impact of climate change. It will be crucial if we hope to save our world. If you would like to know more about SATIM, satellite technology, or innovations in the space industry please contact us
hello@satim.co