Wetlands MEaSUREs – Product Specification Guide

Guide Available in PDF Format

The Alaska Satellite Facility (ASF) DAAC acquired the MEaSUREs (Making Earth System Data Records for Use in Research Environments) Wetlands dataset from the Jet Propulsion Laboratory in 2012. The dataset contains the first level-2, derived synthetic aperture radar (SAR) products available from ASF. The dataset includes a global-scale Earth System Data Record (ESDR) of inundated wetlands to facilitate investigations on their role in climate, biogeochemistry, hydrology, and biodiversity. This ESDR provides an accurate, consistent, and comprehensive global-scale dataset of wetland inundation and vegetation, including continental-scale, multi-temporal, and multi-year monthly inundation dynamics at varying scales.

ASF DAAC’s MEaSUREs Wetlands holdings are available

Data Set Overview

MEaSUREs Wetlands data were gathered from these SAR sensors and satellites: 

  • PALSAR (Phased Array type L-Band Synthetic Aperture Radar)/ ALOS (Advance Land Observing Satellite)
  • QuikScat-EOS (AMSR-E)(Advanced Microwave Scanning Radiometer) (AMSR-E)/Aqua
  • SeaWinds/Quick Scatterometer

Introduction
The MEaSUREs Wetlands project used data from three sources:

  1. PALSAR was one of the three remote-sensing instruments onboard ALOS. ALOS was launched on January 2006 by JAXA for the purpose of acquiring highly precise observations of land coverage. The satellite, which lost power in 2011, used advanced technology to accurately determine spacecraft position and altitude. It was also capable of handling large capacity mission data at high speeds.
  2. Aqua is a NASA Earth Science satellite mission, which launched in 2002 and is named for the large amount of information that the mission is collecting about the Earth’s water cycle—including evaporation from the oceans, water vapor in the atmosphere, clouds, precipitation, soil moisture, sea ice, land ice, and snow cover on land and ice. Additional variables also being measured by Aqua include radiative energy fluxes, aerosols, vegetation cover on land, phytoplankton, and dissolved organic matter in the oceans, as well as air, land, and water temperatures.
  3. NASA’s ocean-observing satellite, QuikScat, was launched in 1999 and was operational for 9.5 months. It carried a SeaWinds scatterometer, and the mission objectives were to:
  • Acquire all-weather, high-resolution measurements of near-surface winds over global oceans.
  • Determine atmospheric forcing, ocean response, and air-sea interaction mechanisms on various spatial and temporal scales.
  • Combine wind data with measurements from scientific instruments in other disciplines to help researchers better understand the mechanisms of global climate change and weather patterns.
  • Study both annual and semi-annual rainforest vegetation changes.
  • Study daily/seasonal sea ice edge movement and Arctic/Antarctic ice pack changes.

The mission’s operational objectives were to:

  • Improve weather forecasts near coastlines by using wind data in numerical weather- and wave-prediction models.
  • Improve storm warning and monitoring.

Program Management

MEaSUREs Wetlands is a NASA/Jet Propulsion Laboratory Earth observation project.

Mission Objectives

MEaSUREs is a NASA-funded program to support research scientists and groups in data product creation, using a multitude of data sources and robust algorithms. These projects generate coherent time series and facilitate the synthesis of datasets in the development of comprehensive Earth system models. The MEaSUREs Wetlands purpose was to construct a global-scale ESDR of inundated wetlands to facilitate investigations on their role in climate, biogeochemistry, hydrology, and biodiversity.

Parameters

1. ALOS was the largest satellite developed in Japan and carried three remote sensing instruments: the along-track 2.5-m resolution Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), the 10-m resolution Advanced Visible and Near-Infrared Radiometer type 2 (AVNIR-2), and the polarimetric PALSAR.

ALOS was launched from JAXA’s Tanegashima Space Center in southern Japan in January 2006. With a total weight of 4,000 kg, ALOS was launched with an H-IIA rocket vehicle, and placed in a sun-synchronous orbit at 691 km, with an orbital revisit period of 46 days.

Fifteen minutes after lift-off, ALOS reached its nominal orbit and separated from the rocket. It established its 3-axis attitude and initiated ground station contact. Communications for tracking and control with local ground stations were performed through the X-band antenna mounted at the nadir side of the satellite body. During nominal operations, this antenna was also used for direct (120-140 Mbps) downlink of Earth observation data.

Additional ALOS parameters are available. A summary table is provided below.

Table 1. ALOS Orbit and Equipment Parameters
Item Characteristics
Orbit Sun synchronous, Sub recurrent
Equator pass time ~10.30 (desc.); ~22.30 (asc.)
Altitude 691.65 km
Inclination 98.16 deg.
Recurrence cycle 46 days
Orbital control +/- 2.5 km (at equator)
GPS orbital position accuracy 1 m (off-line)
Star Tracker attitude determination accuracy 0.0002 deg (off-line) (~2.5 m on the ground)
High-speed Solid State Recorder (HSSR) Capacity: 96 Gbytes
High-speed Solid State Recorder (HSSR) Data rate (max): 360 Mbps (recording)/240 Mbps (playback)
Data transmission: Ka-band antenna 240 Mbps (via DRTS)
Data transmission: X-band antenna 120 Mbps (direct GS down-link)
Solar Array Paddle 3 m x 22 m, 9 segments
Generated power > 7 kW at EOL
Total weight 4000 kg

2. The Aqua mission is a part of the NASA-centered, international Earth Observing System (EOS). Aqua was formerly named EOS PM, signifying its afternoon equatorial crossing time. A timeline of Aqua on-orbit progress through the initial 120-day check-out period.

Aqua was launched on May 4, 2002, and has six Earth-observing instruments on board, collecting a variety of global datasets. Aqua was the first member launched of a group of satellites termed the Afternoon Constellation, or sometimes the A-Train. Additional Aqua parameters are available.

3. NASA’s QuikScat was lofted into space at 7:15 p.m. Pacific Daylight Time on June 19, 1999, atop a U.S. Air Force Titan II launch vehicle from Space Launch Complex 4 West at California’s Vandenberg Air Force Base. The satellite was launched in a south-southwesterly direction, soaring over the Pacific Ocean at sunset as it ascended into space to achieve an initial elliptical orbit with a maximum altitude of about 800 km (500 mi) above Earth’s surface. QuikScat operates in a near polar orbit. It flies in a circular orbit and completes a full orbit in about 101 minutes, which translates to a little more than 14 orbits per day. Additional QuikScat parameters are available.

SAR (Synthetic Aperture Radar) Sensors

1. PALSAR is an enhanced version of the SAR on JERS-1 (L-band; HH-polarization; 35°off-nadir angle). Like its predecessor, PALSAR was developed jointly by JAXA and the Japan Resources Observation Systems Organization (JAROS).

PALSAR is a fully polarimetric instrument, operating in fine-beam mode with single polarization (HH or VV), dual polarization (HH+HV or VV+VH), or full polarimetry (HH+HV+VH+VV). It also features wide-swath ScanSAR mode, with single polarization (HH or VV). The center frequency is 1270 Mhz (23.6 cm), with a 28 MHz bandwidth in fine beam single polarization mode, and 14 MHz in the dual-, quad-pol and ScanSAR modes. The off-nadir angle is variable between 9.9° and 50.8° (at mid-swath), corresponding to a 7.9-60.0° incidence angle range. In 5-beam ScanSAR mode, the incidence angle range varies from 18.0° to 43.0°.

The antenna PALSAR consists of 80 T/R modules on 4 segments, with a total size of 3.1 by 8.9 m when deployed. As a result of the relatively small antenna size, orbit altitude, and large Doppler bandwidth, the pulse repetition frequency varies (1500-2500 Hz) along the orbit.

Table 2. PALSAR Specifications
Item Specifications
Center frequency 1270 MHz / 23.6 cm
Chirp band width 28 MHz (single polarization),
14 MHz (dual, quad-pol., ScanSAR)
Transmission power 2 kW (peak power)
Pulse Repetition Frequency 1500 – 2500 Hz (discrete stepping)
Image modes Single polarization (HH or VV), Dual pol. (HH+HV or VV+VH), Quad-pol. (HH+HV+VH+VV),

ScanSAR (HH or VV; 3/4/5-beam)
Bit quantization 3 or 5 bits (5 bits standard)
Off-nadir angle Variable: 9.9 – 50.8 deg. (inc. angle range: 7.9 - 60.0),
ScanSAR: 20.1-36.5 (inc. 18.0-43.3)
Look direction Right
Yaw steering ON
Swath width 70 km (single/dual pol. at 41.5°),
30 km (quad-pol. at 21.5°)
350 km (ScanSAR 5-beam)
Ground resolution
Rg (1 look) x ~ 9 m x 10 m (single pol. at 41.5°),
~ 19 m x 10 m (dual pol. at 41.5°),
~ 30 x 10 m (quad-pol. at 21.5°),
~ 71-157m (4 look) x 100m (2 look)
Az (2 looks) (ScanSAR 5-beam)
Data rates 240 Mbps (single/dual/quad-pol) 120 or 240 Mbps (ScanSAR)

2. AMSR-E is a 12-channel, six-frequency, total power passive microwave radiometer at all channels. The Earth-emitted microwave radiation is collected by an offset parabolic reflector 1.6 meters in diameter that scans across the Earth along an imaginary conical surface, maintaining a constant Earth incidence angle of 55° and providing a swath width array of six feedhorns, which then carry the radiation to radiometers for measurement. Calibration is accomplished with observations of cosmic background radiation and an on-board warm target. Spatial resolution of the individual measurements varies from 5.4 km at 89.0 GHz to 56 km at 6.9 GHz.

AMSR-E Instrument Characteristics

  • Passive microwave radiometer, 12 channels, 6 frequencies, dual polarization, conically scanning.
  • Measures precipitation rate, cloud water, water vapor, sea surface winds, sea surface temperature, ice, snow and soil moisture.
  • All-weather measurements of geophysical parameters supporting several global change science and monitoring efforts.
  • External cold load reflector and a warm load for calibration.
  • Offset parabolic reflector, 1.6 m in diameter, and rotating drum at 40 rpm.
  • Multiple feedhorns (6) to cover six bands from 6.9 to 89 GHz with 0.3 to 1.1 K radiometric sensitivity; vertical and horizontal polarization.

3. The SeaWinds on QuikScat mission is a “quick recovery” mission to fill the gap created by the loss of data from the NASA Scatterometer (NSCAT), when the satellite carrying it lost power in June 1997. The SeaWinds instrument on the QuikScat satellite is a specialized microwave radar that measures near-surface wind speed and direction over Earth’s oceans under all weather and cloud conditions.

SeaWinds uses a rotating dish antenna with two spot beams that sweep in a circular pattern. The antenna radiates microwave pulses at a frequency of 13.4 GHz across broad regions on Earth’s surface. The instrument will collect data over ocean, land, and ice in a continuous, 1,800-km-wide band, making approximately 400,000 measurements and covering 90 percent of Earth’s surface in one day.

SeaWinds Instrument Characteristics

  • Radar: 13.4 GHz; 110-watt pulse at 189-Hz pulse repetition frequency (PRF)
  • Antenna: 1-m diameter rotating dish that produces two spot beams, sweeping in a circular pattern
  • Mass: 200 km
  • Power: 220 watts
  • Average Data Rate: 40 KB per second

Data Acquisition and Processing

Data were collected using the following SAR sensors and satellite missions:

  • PALSAR/ALOS
  • AMSR-E/Aqua
  • SeaWinds/QuikScat.

Data were processed by the MEaSUREs Wetlands team:

Principal Investigators
Kyle C. McDonald, Ph.D.
Terry Elkes Professor, Department of Earth and Atmospheric Sciences
CUNY Environmental Crossroads Initiative and CREST Institute
The City College of New York, City University of New York
MR 925, 160 Convent Ave. & W. 138th St., New York, NY 10031 USA
Phone: 212-650-8218; Mobile: 818-434-8937; FAX: 212-650-7064

AND

Jet Propulsion Laboratory, California Institute of Technology
4800 Oak Grove Drive; Pasadena, California 91109-8099 U.S.A.

Project Members
Bruce Chapman (JPL)
Laura Hess (University of California, Santa Barbara)
Mahta Moghaddam (The University of Michigan)
John Kimball (University of Montana)

Collaborators
Dr. Martti Hallikainen (Helsinki University of Technology)
Ake Rosenqvist (JRC — Italy)
Masanobu Shimada (EORC-JAXA — Japan)
Max Finlayson (International Water Management Institute)
Nick Davidson (Ramsar)
Wenjun Chen (CCRS)
Albert Jimenez (Columbia University)
Adane Metaferia (California State University, Chico)

Data Description

Spatial Characteristics
The ESDR is comprised of two complementary components:
1. Fine-resolution, 100-m maps of wetland extent, vegetation type, and seasonal inundation dynamics, derived from SAR for continental-scale areas covering crucial wetland regions.

2. The second component is comprised of global monthly mappings of inundation extent at ~25 km resolution.

Data Naming Convention
ASF’s MEaSUREs Wetlands data products do not follow a strict naming convention. Examples of common naming schema are below:

  • alaska_wetlands_map.tif
  • 20070104_430_HH_003_19M.cls
  • south-america-alos-scansar.gif

GeoTIFF Product (.tif)

GeoTIFF is a public domain metadata standard that allows georeferencing information to be embedded within a TIFF file. The GeoTIFF data products are geocoded to the Universal Transverse Mercator (UTM) map projection, using the zone that best represents the data’s geolocation. The ASF MEaSUREs Wetlands GeoTIFF products have the file extension .tif.

GIF Product (.gif)
The Graphics Interchange Format is a bitmap image format supports animations and allows a separate palette of up to 256 colors for each frame. GIF images are compressed using the Lempel-Ziv-Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality.

Data Quality Issues

Please refer to the following publication for a detailed description of data quality issues associated with the Alaska Wetlands Map:

Alaska Wetlands Map derived from JERS-1 data. Whitcomb, J., M. Moghaddam, K. McDonald, J. Kellndorfer, and E. Podest, “Mapping wetlands of Alaska from L-band SAR imagery,” C. J. Remote Sensing, vol. 35, no. 1, pp. 54-72, February 2009. 

For other data quality questions, please contact:

Principal Investigator Kyle C. McDonald, Ph.D.
Terry Elkes Professor, Department of Earth and Atmospheric Sciences
CUNY Environmental Crossroads Initiative and CREST Institute
The City College of New York, City University of New York
MR 925, 160 Convent Ave. & W. 138th St., New York, NY 10031 USA
Phone: 212-650-8218; Mobile: 818-434-8937; FAX: 212-650-7064
https://www.ccny.cuny.edu/profiles/kyle-mcdonald

OR

Jet Propulsion Laboratory, California Institute of Technology
4800 Oak Grove Drive; Pasadena, California 91109-8099 U.S.A.
http://science.jpl.nasa.gov/people/McDonald

Using MEaSUREs Wetlands Products

The MEaSUREs Wetlands data products are currently supported to varying degrees by a number of software tools and packages that can be used to investigate and visualize the data.

Data exploration through the ASF Wetlands data portal

ASF’s time-series tool allows users to easily visualize wetland inundation dynamics across the globe by letting users select a point on a map interface that generates a graph of wetlands inundation and/or snow cover.

Data exploration through other software packages

  1. ENVI is a commercial geospatial software that processes and analyzes imagery. It integrates with ArcGIS® from Esri. 
  2. Google Earth
  3. GDAL
  4. ArcGIS® from Esri is a commercial geography platform enabling users to create, organize, and share geographic information and tools with anyone by using intelligent online maps and useful apps.
  5. MapReady

Data Access

To Obtain ASF MEaSUREs Wetlands Data:

Data are available to users under NASA’s open-access data policy. 
View and download holdings.

For more information, visit the Alaska Satellite Facility website.

Contact Information:
Alaska Satellite Facility
Geophysical Institute
2156 Koyukuk Dr.
P.O. Box 757320
Fairbanks, AK   99775-7320

Phone: (907) 474-5041
Fax: (907) 474-2665
Email: uso@asf.alaska.edu

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document:

ALOS Advanced Land Observation Satellite
AMSR-E Advanced Microwave Scanning Radiometer — EOS
ASF Alaska Satellite Facility
AVNIR-2 Advanced Visible and Near-Infrared Radiometer type 2
Az Azimuth
CCRS Canada Centre for Remote Sensing
EORC-JAXA Earth Observation Research Center-Japan Aerospace Exploration Agency
EOS Earth Observing System
ESDR Earth System Data Record
GPS Global Positioning System
GHz GigaHertz
HSSR High-speed Solid State Recorder
JAROS Japan Resources Observation Systems Organization
JAXA Japan Aerospace Exploration Agency
JPL Jet Propulsion Laboratory
JRC Joint Research Centre, European Commission
MEaSUREs Making Earth System Data Records for Use in Research Environments
NASA National Aeronautics and Space Administration
NSCAT NASA Scatterometer
PALSAR Phased Array L-Band Synthetic Aperture Radar
PRF Pulse Repetition Frequency
PRISM Panchromatic Remote-sensing Instrument for Stereo Mapping
QuikScat Quick Scatterometer
Rg Range
SAR Synthetic Aperture Radar
TIFF Tagged Image File Format
UTM Universal Transverse Mercator

Last updated: September 20, 2013