Ground based and Satellite Radar, the Mining Power Couple
Terrestrial and orbital InSAR need each other, and we need them too, now more than ever.
Let’s begin by naming one of the great challenges of remote sensing, acronyms. We have literally a soup of them: DinSAR, PSinSAR, satSAR, TS, so let’s do that famous experiment together of explaining this as tho our readers really don’t have a PhD in radar processing :)
Our side of the equation at Ovela is that of the space based radar service provider. That means we process radar data from space craft to create insights which we map in a way that anyone should be able to understand. However, we have a tremendous power when combined with a ground based radar device.
From orbit we can determine the long term trend, and the forensic history of motion. This is tremendously valuable. End-users can then go back in time to see how a high rainfall event, seismic activity, or wind storm correlated to the deformation they are observing and better plan to mitigate risks from those sources in the future.
When we determine, from orbit, that an issue reaches a critical state and failure could occur within days or hours operators can then collaborate with both our data and a ground based radar provider like John Metzger and IDS georadar.
With the increased focus on tailings dam safety from mining operations, and honestly the ageing of key infrastructure broadly we need the harmony of these two platforms to be common place.
Ground based radar systems allow operators to scan the surface of a landslide or other area from a safe distance without attaching sensors to the area in question. Operators then get a data feed from the radar platform of deformation updating minute by minute allowing them to know when to move critical staff in more real time than possible from a satellite platform: minutes in place of days.
Where do you find ground radar systems?
Mining, the industry with acute deformation challenges is the largest consumer of ground based radar device usage. It has a lot to gain from fusing satellite radar to its understanding of the wider and longer time scale site perspective. The tragedy of the Brumadinho dam failure in Brazil brought this to everyone’s attention. Tailings dams can display slow, long term deformation trends that can accelerate in a matter of days to a failure condition. Ovela forensic radar processing showed the failure at Brumadinho months before it occurred, as the deformation rates accelerated. At that point it would have been ideal to add a ground based radar device to monitor the site providing real time data to engineers.
What about real time satellite data?
Space craft such as TerraSarX (TSX) can also provide near real time InSAR data on critical sites. They can play a role together with space craft such as Sentinel 1 to fill in where ground radar cannot be placed or there isn’t time. However, the option of first choice really should terrestrial radar units in conjunction with satellite radar. The cost of TSX is prohibitive to most users, and its scheduling cannot typically be coordinated rapidly.
When small sat constellations such as ICEYE and RadarSAT3 are in full operation and providing phase data in near real time this could prove a viable option to drive down costs.
We need Terrestrial and Orbital Radar to collaborate
Born of research institutions and government studies the radar deformation monitoring industry is still a niche of a niche. End users and providers can realise tremendous benefits in situational awareness and monitoring efficacy with the two platforms in harmony. We’ve not touched on the need to add in situ (on site) measurement devices to this integrated assessment. Many IoT / SCATA harmonising platforms are emerging, such as sensmetrics to bring those systems together. When we can add terrestrial and orbital radar to the assessment picture we can create an astounding amount of data on a site.
A meanings foot note
So lets quickly do a gist of what these various acronyms we mentioned mean and why they matter… for the dedicated among you :)
SAR - synthetic aperture radar, the concept of a synthetic aperture comes from the fact that without some astounding physics driven algorithms you would need a massive radar array to resolve the accuracy needed to produce actionable data. So satellite operators create a synthetic aperture from those algorithms so you get useful data.
InSAR - interferometric SAR, this technique allows processors like Ovela to see where the radar images overlap in a stack so that we can check for variations in the images and derive accurate deformations.
DinSAR - differential inSAR, this is the comparison of very few radar images and was very useful when we didn’t have Sentinel1 to give a large volume of images. DinSAR is notoriously less precise than persistent scatters but it does allow you to see dramatic changes: building there / building not there
PSinSAR - persistent scatter inSAR, is a technique to see a persistently scattering point through a large number of radar images. This allows you to very accurately determine the motion of that pixel through time, known as TS or time series. This is the technique used by Ovela in Sille so our end users have the most accurate data to make decisions from. While it can result in fewer radar points than DinSAR, they are far more accurate.