Alaska Satellite Facility
Delivering Remote Sensing Data Since 1991

The Importance of Monitoring Wetlands

Wetlands help control climate, filter and purify water, cycle carbon and water, control flooding, stabilize shorelines, and are the most biologically diverse of all ecosystems. Yet much about wetlands remains to be discovered, in part because of their complexity and inaccessibility.

Wetlands can hold freshwater, brackish water or saltwater, and they can take the form of swamps, marshes, bogs, or fens. Their secrets range from how much of the planet they occupy to the details of how they affect and are affected by climate. Remote sensing gives scientists powerful tools for collecting wetlands data on their distribution and dynamics. These data enable researchers to map habitat, identify vegetation types, time the rise and fall of water levels, and more. Spaceborne microwave sensing is particularly sensitive to surface water and vegetation structure, and it allows monitoring of large inaccessible areas over time regardless of atmospheric conditions or solar illumination.


MEaSUREs (Making Earth System Data Records for Use in Research Environments) is a NASA-funded program to support research scientists and groups in data product creation, using a multitude of data sources and robust algorithms. MEaSUREs projects generate coherent time series and facilitate the synthesis of data sets in the development of comprehensive Earth system models. The products are subject to rigorous standards for data quality, validation, algorithm description, documentation, and delivery.

ASF archives and distributes the MEaSUREs Wetlands project, which has constructed a global-scale Earth System Data Record (ESDR) of inundated wetlands to facilitate investigations on their role in climate, biogeochemistry, hydrology, and biodiversity.

The data record has two parts:

  1. Fine-resolution, 100-meter, maps of wetland extent, vegetation type, and seasonal inundation dynamics, derived from Synthetic Aperture Radar (SAR) for continental-scale areas covering crucial wetland regions. These were created with newly available data (HH/HV) from the Phase Array L-Band SAR sensor mounted on the Advanced Land Observing Satellite built and operated by the Japan Aerospace Exploration Agency. The wetland products were generated using algorithms based on an object oriented image segmentation approach and a statistically based decision tree classifier.
  2. Global, 10-day mappings of inundation extent at ~25 km resolution derived from multiple satellite remote sensing observations including passive and active microwave sensors and optical data sets optimized specifically for inundation detection. A clustering model and a mixture model comprise the classification and fractional inundation calculations of the algorithm used. Monthly data were used to construct annual summary products, including maximum spatial distribution and area, and annual inundation duration of inundated wetlands.

MEaSUREs scientists now plan comparative analyses of various high-resolution products and low-resolution inundation mappings in order to ensure consistency and accuracy of ESDR products.


ASF focuses on synthetic aperture radar data as one of 12 theme-based NASA Earth science data centers in the nation known as Distributed Active Archive Centers (DAACs). The DAACs are major components of the Earth Observing System Data and Information System (EOSDIS), which in turn is part of NASA’s Earth Science Data Systems Program.

Links to additional MEaSUREs data at ASF and other DAACs:

This landmark, high-resolution map of Alaska wetlands, published in 2009, was created with mosaics of radar imagery. © JAXA 1993-1998.This landmark, high-resolution map of Alaska wetlands, published in 2009, was created with mosaics of radar imagery. © JAXA 1993-1998.
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