Earth observation (EO) satellites create increasingly significant volumes of data with far-reaching global coverage. The application of EO satellite data and geospatial information, coupled with analysis and innovation in technology deliver great impact to important environmental, economic and social policies at local, regional and even global scales.
A range of software (open source and proprietary), tools, and analysis platforms exist for accessing, storing, processing, and facilitating the use of EO satellite data. Open Data Cube (ODC) technology, for example, increases the value and impact of EO satellite data by providing an open and freely accessible architecture. The combination of EO satellite data and such platforms enables users to easily integrate EO satellite data to provide new insights and support better policy-making across a diverse range of issues from water resource management to urbanization and environmental accounting.
ODC Technology to Quantify Nationwide Land-use Change
The Pollutant Inventories and Reporting Division (PIRD) in Canada was tasked with creating a greenhouse gas inventory of the country and a key part of this analysis is the use of remotely sensed data to quantify areas of land-use change to calculate CO2.
But quantifying the impact of land-use change on greenhouse gases is complicated. The amount of emissions and sequestrations of greenhouse gases for a developed area varies depending on the change that occurred.
“We have to understand not only what areas changed, but what they changed from and what they become afterward,” Doug MacDonald, Ph.D., manager of the Land Use Section at PIRD, told GIM International. “What the land becomes influences the total carbon balance.”
For example, when developing a residential community, a certain amount of CO2 sequestrated in the soil is emitted into the atmosphere. Yet, the new neighborhood will likely have grass and trees and, to some degree, these will contribute to sequestration.
“The biggest challenge is monitoring change in a land sector the size of Canada,” said MacDonald. “It’s difficult to capture all the diverse changes that happen across the Canadian landscape.”
Canada is the world’s second-largest country, stretching across 3.8 million square miles (9.9 million square kilometers), where thousands of miles of previously unindustrialized land area have been transformed into residential areas, shopping centers, office buildings, etc. Therefore, PIRD will have to perform multi-temporal change detection analysis on satellite images spanning decades.
In order to do this, the agency partnered with PCI Geomatics, a Toronto-based provider of geospatial software, to leverage ODC technology to enhance the efficiency, accuracy, and granularity of analyzing the enormous volumes of data.
Monitoring the Murray-Darling Basin from Space
The Murray-Darling Basin (the Basin), located in southeast Australia, is one of the most important agricultural regions in the country. It covers more than 386,000 square miles (one million square kilometers) and runs across the Australian Capital Territory (ACT), parts of Queensland, New South Wales, Victoria, and South Australia. The Basin includes 23 river valleys and 48,000 miles (77,000 kilometers) of rivers. It is home to more than 30,000 wetlands, some of which are fundamental to the health and viability of the whole region.
In 2012, the Basin Plan passed into law in Australia as a major step forward for managing this complex system. It provides a coordinated approach to water use across the Basin’s four states and the ACT. It was a major step forward in Australian water reform. But on July 2017, an episode of Four Corners, aired on ABC and made allegations of substantial water theft in the Basin. In response, more proactive approaches to environmental water protection rules and policies were adopted.
A crucial part of these new approaches is the testing and trialing of the use of remote sensing, particularly the use of EO satellites, to assist with future compliance checking and investigation. EO satellite data provides an important method for consistently measuring water use and water presence over spatial scales as large as the Basin.
In order to help manage the water in the Basin, Geoscience Australia and the New South Wales government are leveraging one of Australia’s first analysis-ready data platform, Water Observations from Space (WOfS). It detects water on the land surface from Landsat imagery. Australia uses the WoFS algorithm, updated for every Landsat pass, and a map of the locations and spatial extent of over 60,000 water storages—referred to as farm dams—to estimate how full these farm dams are on a monthly basis.
WOfS provides an understanding of where water is at present, where it is seldom observed, and where inundation of the surface has been occasionally observed by EO satellites.
Mapping Natural Resources
For more than 50 years, the Geographic Division in the National Institute of Statistics and Geography (INEGI), the National Mapping Agency in Mexico, has been tasked with producing maps for multiple purposes such as topographic, census area, water, soils, climate, and vegetation maps for the entire country. With its mapping efforts based on remotely sensed imagery, the INEGI needed a way to manage, process, and analyze the massive amounts of EO satellite data in an effective way.
Efforts to enhance the analysis of the Earth’s surface with EO satellites have led the scientific community to develop different techniques and methodologies. The ODC, an open-source solution for accessing, managing, and analyzing large amounts of data,increases the value and impact of EO satellite data by providing an open and freely accessible framework where multiple data sources can produce information for multiple uses.
INEGI has initiated a collaboration with Geoscience Australia, a collaborator of ODC, to detail a local implementation of ODC in Mexico. The goal is to implement ODC’s open source technology and adopt it in the agency’s processes related to EO satellite images.
By leveraging the ODC framework, it is possible to execute different algorithms, perform supervised and unsupervised classifications, extract training samples efficiently, and identify and fill contaminated pixels (cloud, cloud shadow) with optimal pixels from the dataset archive.
Using ODC technology INEGI expects to promote more timely and accessible information, varied geospatial and statistical data about natural resources and the environment, and encourage the exchange of data analysis methodologies.
Featured Image: Conversion of raw satellite imagery to Analysis Ready Data using PCI Geomatics ARD Tools (from left: RGB, Spectral based pre-classification, topographically normalized ARD image) | Photo Credit: GIM International