NISAR Updates from Sisters of SAR
All of us in the SAR world who routinely use Copernicus Sentinel-1 data will agree that NISAR is the next big thing. So we have news for you! For those of you who might not know, NISAR (NASA-ISRO SAR mission) is joint Earth Observation SAR mission between NASA (National Aeronautics & Space Administration) and ISRO (Indian Space Research Organisation). It is is due for launch aboard a GSLV launcher from the Satish Dhawan Space Center in Sriharikota, India in 2023. It will be the world’s first dual frequency SAR satellite sensor, with the capacity to collect & receive both L and S-band SAR data, every 6 days in the ascending and descending orbits with a repetition rate of 12 days. The baseline mission lifetime is three years and all the data will be available free and open. It also aims to acquire images with consistent geometry, look directions and incidence angles, through time, on a per-pixel basis. Now this is important as it allows not only to capture changes in backscatter per pixel, allowing for a pixel based time series analysis, but also in phase. The changes in SAR backscatter depend on target scene/object characteristics like surface roughness, soil moisture content, foliage, dielectic constants. Measurement of phase changes allows a technique called interferometric SAR (InSAR), wherein we can measure small scale changes on the Earth’s surface. The mission also plans to acquire data at high/medium spatial resolutions too, 3-10 m depending on the mode, and over most land surfaces coherent dual pol HH and HV data.
The NISAR resources from the two space organisations are also great places to learn about the mission and the SAR techniques that it will allow.
InSAR is awesome! And not just because it allows us to analyse and monitor deformation on the Earth’s surface from Space. When satellites acquire images of the same area with consistent geometries, such as planned for NISAR, a technique called InSAR can be used to exploit phase changes in the data and measure coherence. These can be related to changes on the Earth’s surface- monitoring subsidence and uplift, deformation post Earthquakes, deformation from volcanic eruptions, monitoring agriculture practices like tillage and harvesting and so on. It involves a bunch of steps and if you’ve done everything correctly, and your reference and secondary images are a match, you will get these beautiful fringe patterns in front of you showing changes on the Earth’s surface in the most beautiful of colours.
Lets talk a little about SAR polarimetry. A dual-polarimetric SAR sensor is capable of sending the signal in one particular polarisation, either Horizontal (H) or vertical (V) but can receive the signal in either of the two polarisation. So when SAR users talk of HH, HV, VV, HH, they refer to the nature/polarisation of the signal during transmission & reception, the first letter indicating the sent direction and second, the received direction. Being able to transmit and receive signals in these different polarisations allows for a technique called SAR polarimetry wherein we can differentiate between different objects on the Earth’s surface based on how they change/alter the sent SAR signal’s polarisation. Sensors like TerraSAR.X are quad-pol sensors which mean they can send signals in two directions and receive them in two directions thereby giving us, wait for it, VV,VH,HH and HV polarised images.
For those who have not crossed over to the Grayscale side, the SAR side, you will find tonnes of resources about SAR, SAR polarimetry and SAR interferometry on our Sisters of SAR resources page:
NISAR Science meeting updates
Getting back to NISAR, recently, a NISAR Science meeting/workshop took place at JPL Pasadena and Sisters of SAR was present and represented by Sarah Banks. Here are some important updates from the workshop:
- launch is now scheduled for January 29th, 2023.
- S-band data will have limited coverage and will be acquired over India and a few other sites.
- NISAR will be using a technique called ‘Sweepsar’ to achieve very wide swaths > 240 km, maximise ratio of signal to noise, and reject range ambiguities.
- From these data, a number of level 3 products (read also as Analysis Ready Products?) will be generated, including a global soil moisture product.
- The NISAR mission aims to achieve certain accuracy requirements for their level 3 products (e.g., 80% for soil moisture over a 2 hectare area)
- Level 2 products will be in UTM coordinates and level 3 in equal area, called easy grid format (but there is still time for the community to provide feedback to change this to UTM)
- Grid will be deterministic throughout the life of the mission, so pixel location on one scene will be the same through time, allowing users to select on pixel and do time series datacube analysis
- Several algorithms will be available on Github so that users can generate their own level three products, including algorithms to quantify woody biomass, vegetation disturbance, wetland inundation, crop area and more.
- NISAR will not produce a global biomass product, but code will be available to implement it
- There is still time to change a few things (e.g., projection or add a global biomass product), but they need to know the community wants it and need funding partners
- The NISAR team is still looking for cal-val sites for soil moisture and other products so if you work in such a team, get in touch! NISAR will have established methodologies that people can implement to make their site useful for cal val
Finally, future NISAR users can still apply to become early adopters and gain access to simulated NISAR data that they can begin testing. At the meeting, a number of different funding opportunities were announced. This includes DEVELOP which is an applied sciences training program where participants are given experience applying Earth observations by working on interdisciplinary projects and are mentored by science advisors from NASA and partner agencies.
If you have not done so, go to the NISAR links above for more information. Or get in touch with Sisters of SAR and we’ll point you in the right direction.
Key takeaways from Geo for Good 2022 – geo product updates, impacts, and diversity and inclusion
Professor Iain H Woodhouse, Knowledge and Outreach Lead at Earth Blox, shares updates from Google’s annual event for the changemakers making a positive impact in the world.
Every year, at the Geo for Good Summit, Google brings together nonprofits, scientists and other changemakers who want to leverage their technology and mapping tools such as Google Earth, Earth Engine, Environmental Insights Explorer, and My Maps for positive social and environmental projects. The event has been running since 2011, and for the last two years, was held online due to the pandemic. This year, the event was a hybrid, with some 300 delegates coming together in-person in Mountain View, California and over 2,000 joining in online from around the world.
Geo for Good combines plenary sessions, workshops, demo stations and panel discussions delivered by a wide range of experts from Google and the community. So what did we learn? Below are my key takeaways from the event.
Geo Product updates – what’s new in Google Earth, MyMaps, Earth Engine and Environmental Insights Explorer
The latest update from Google Earth included news about a forthcoming new UI that will support better data management and editing. And combined with new cross-platform interoperability, it is going to be even easier than ever to use GE in the field. This includes being able to easily upload photos and location, wherever you are.
MyMaps is Google’s lightweight mapping tool to make it easy to make maps, import Sheets data and share with others. It is now possible to sync between Sheets and Maps so they can be kept updated, and merging multiple datasets is now easier than ever.
And for Earth Engine (apart from the big news of the year about them moving to a commercial offering) the key updates were in the new data added to the catalogue. This includes data from the new Landsat 9 continuing the multi-decade Landsat dataset, additional data from the canopy laser scanner on the ISS, GEDI ( L4B 1km gridded biomass and L2A top height) and the new inclusion of the Dynamic World land classification layer. Dynamic World is updated with every Sentinel 2 image acquisition, and provides a % probability that a pixel lies within one of the 9 classes. Built in collaboration with WRI, this 10m resolution data layer can be used as a land cover classification layer “as is”, but it can also be used as an input layer to create new locally-specific land cover classifications. Incredibly powerful, and it will be amazing to see its full potential, especially when we include it within Earth Blox.
Finally, we also saw an introduction to the new Google Environmental Insights Explorer. This is designed to help city planners adapt to low carbon economies by tracking carbon emission inventories. It incorporates transport and building emissions (using Google Maps data) and calculates the total solar rooftop potential of buildings inside a city. They have now expanded the building coverage to 14,000 cities for as much as four years of historical data for some cities. The most recent addition (for some cities) is a tree canopy map for tracking urban trees.
With the announcement earlier this year that Google is now offering commercial access for Earth Engine there was also a lot of interest in the session on “Sustainability Impacts: A Commercial Perspective” where Brian Sullivan and Jen Bennett described how Earth Engine and Google Cloud Platform are coming together to achieve sustainability impacts. Google-wide, they have ambitious targets for the company to go “beyond carbon neutral” and to support their partners (companies, non-profits, researchers, policymakers, etc) to scale up climate solutions. They see Earth Engine as one of these scalable solutions, with huge impacts on protecting the world’s forests by working with WRI on Global Forest Watch, and with Unilever on helping create deforestation-free supply chains.
Earth Engine for Non-Coders
Making geo technologies accessible is critical to accelerating and scaling solutions in the fight against climate change. At Earth Blox, our mission is to increase access to big Earth data to accelerate the transition to a much more sustainable, equitable and inclusive world. We do this today through a no-code interface to Google Earth Engine and so understanding the beginner’s journey is really important to us.
Projects making an impact
The Community Talks at Geo for Good are a highlight as this is where we get to see the real world applications of the technology and the problems it is solving. Perhaps two of the most inspirational projects were Navajo Nation drought monitor and the search for the Andean Cat.
Dr. Rocio Palacios, from the Andean Cat Alliance, explained how the Andean Cat has been an elusive species, only being tracked down as recently as 20 years ago. It is a small cat, not much bigger than a domestic cat, but has an important role in Andean folklore and is sacred amongst indigenous groups of the area. But it is at risk, with only 1,400 adult Andean Cats known to be alive across four countries: Peru, Bolivia, Chile, and Argentina. With such a low population density, it is a hard species to study, but with the help of Google Earth Pro, Dr Palacios and her team have managed to evaluate the cat’s ecosystem and set camera traps that have allowed them to create the first ever comprehensive population assessment map. The accessible nature of Google Earth has ensured that the process has brought together a range of stakeholders, including isolated communities, so that instead of being invisible, the Andean Cat is now “in everyone’s mind”.
Working with the Navajo Nation, Nikki Tulley, from BAERI/NASA Ames Research, has been developing the Drought Severity Evaluation Tool, an Earth Engine app that monitors drought conditions in the Navajo Nation. It allows easy access to analyse and visualise the data, and creates on-the-fly maps and time series graphs for users from non-technical backgrounds. A key message of this project was about recognising the sovereignty of indigenous nations. Often when using satellite data it is easy to forget that there are histories, traditions and beliefs that need to be recognised and included through consultation and engagement with the people who are connected to the landscape being observed from space.
Diversity and inclusion
A key plenary session was the panel on An Inclusive Future for the Geo for Good Community, which asked the question what does an inclusive future mean to you, and what actions can we take as individuals and as a community to make it a reality? Excellently introduced and moderated by Morgan Crowley (Ladies of Landsat) and Sabrina Szeto (Women+ in Geospatial) the session panel provided a strong collective message in support of diversity and inclusion in the geospatial industry. Our own Genevieve Patenaude was also one of the panel members, and those of you who saw her heartfelt presentation at the Living Planet Symposium earlier this year will know she’s a passionate advocate for equality, diversity and inclusion in all things “geo”, and at the root of it all is simply being kind.
Ultimately, we loved attending Geo for Good 2022 because we were able to meet so many people in person that we’ve only met via Google Meet or social media. Earth Blox is a people-centric company, so conversations with speakers and Google staff over a coffee or lunch is always inspiring. The great thing about Geo for Good is that you can meet the people that make the tools, and if you don’t meet them at break times, you can find them camped out in little tents around the venue with bookable time-slots to sit and ask questions of the experts. Whether it’s how to wrangle some data on Earth Engine or importing GeoTIFFs into Google Earth, whatever your problem there is someone there to help. It really is a “festival of geo.” If you get the opportunity to attend in person, seize it. I promise you won’t regret it.
We invite the Geoawesome community to register for free, early access to Earth Blox – use the code Geoawesome22.