Terrestrial Ecology – How To Cite

Citing Terrestrial Ecology Dataset

Cite datasets in publications such as journal papers, articles, presentations, posters, and websites. Please send copies of, or links to, published works citing data, imagery, or tools accessed through ASF to uso@asf.alaska.edu with “New Publication” on subject line.

Also see ALOS PALSAR Terms and Conditions and How to Cite ALOS-1 PALSAR data.

Format Example
Dataset: SAR Subsets for Selected Field Sites, ASF DAAC, ORNL DAAC, 2010. Retrieved from] ASF DAAC [day month year of data access]. Includes Material © JAXA/METI [year of data acquisition]. Dataset: SAR Subsets for Selected Field Sites, ASF DAAC, ORNL DAAC, 2010. Retrieved from ASF DAAC 11 June 2015. Includes Material © JAXA/METI 2007.

Crediting Terrestrial Ecology Imagery

Include credit with each image shown in publications such as journal papers, articles, presentations, posters, and websites.

Format Example
[creator credit, year created]; Includes Material © JAXA/METI [year of data acquisition]. ASF DAAC, ORNL DAAC 2010; Includes Material © JAXA/METI 2007.

Terrestrial Ecology – Data Acquisition

Imagery from synthetic aperture radar (SAR) satellites is not a familiar data set for most users of geographic information systems (GIS). There are several reasons why radar imagery is not commonly used, primarily because of the nature of the technology and its specialized applications. Another is that radar imagery is not optical, requiring more technical processing and specialized image interpretation skills.

Overview

The SAR satellite used to create these images is the Advanced Land Observing Satellite (ALOS). ASF is an archive facility for ALOS data collected over the Americas. The SAR sensor is an L-Band phased array radar capable of imaging in several resolutions and polarizations. Because radar data is ranging data that measures the strength and scatter of the radar pulse, it is not like optical imagery which is visually intuitive. To make the SAR scenes more user friendly, the polarization data was classified as reds, greens, and blues in the image. Another aspect of radar remote sensing is that the ranging data must be terrain-corrected by a process that assigns the ranging values to geographic coordinates by utilizing a digital surface model (DSM). High resolution DSM data are not available for the entire planet and existing data at high latitudes is problematic, especially in areas of very little terrain relief, such as sheet glaciers. To use a consistent DSM for this project and all of the sites being investigated, the DSM data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging instrument was used for the terrain correction.

ALOS PALSAR

Launched on January 24th, 2006 aboard the Advanced Land Observing Satellite (ALOS), the Phased Array Type L-band Synthetic Aperture Radar (PALSAR) instrument has promising applications for natural resource and land applications including parameters applicable to terrestrial nutrient cycle estimates. Research has shown that SAR data by itself, or combined with other optical or active systems, can enhance land characterization with information not otherwise available from passive remote systems. Because Radar emits its own signal, imaging can occur anytime of the day or night independent of sun angle. This is in contrast to passive imaging systems that require the Sun’s illumination. Due to its longer wavelength than visible light, the microwaves used in Radar also have the advantage of not being impeded by cloud cover or other atmospheric contamination. Some examples of PALSAR land applications include estimates and mapping of vegetation above ground biomass, deforestation mapping, wetland (including high latitude) characterization, and cropland monitoring.

Radar Imaging Basics

The PALSAR instrument is a type of Synthetic Aperture Radar (SAR) that emits energy in the long wavelength L-Band (1270 MHz) frequency. SAR radar systems are able to generate high-resolution imagery with a synthetic aperture (or virtual long antenna) by combining signals received by the physically short (real) antenna as it moves along its flight track.

As an imaging radar system moves along a flight path it emits and receives pulses in a single particular microwave wavelength and orientation (waves polarized in a single vertical (V) or horizontal (H) plane). The radar pulse interacts with the Earth’s surface and is scattered in all directions, with some energy reflected back toward the radar’s antenna. Known as backscatter, the returned signal is received by the antenna a fraction of a second later and in a specific polarization (H or V). The brightness, or amplitude, of the backscatter is measured and recorded and the data are used to derive an image. Radar waves interact differently with soil, vegetation, water, ice, and man-made objects such as buildings and roads because the backscatter is affected by the surface properties of objects. For a smooth surface such as water or a road, most of the incident energy is reflected away from the radar system resulting in a very low return signal. In contrast, rough surfaces will scatter the emitted energy in all directions and return a significant portion back to the antenna. In general, vegetation is usually moderately rough with most radar wavelengths.

Terrestrial Ecology – Data Application

PALSAR Terrestrial Biophysical Applications

The data can be used for a number of purposes: (1) to validate the synthetic aperture radar (SAR) measurements using flux tower site characterization data; (2) to examine the impacts of vegetation dynamics on climate; (3) to understand human impacts on vegetation at a local scale; (3) to detect deforestation and forest degradation; (4) to map and differentiate growth stages and change; (5) to retrieve woody biomass and structural attributes; and (6) to characterize, map and monitor ecoregions such as mangroves and wetlands.

Satellite radar can be important to Earth system monitoring because the properties of the signal return are better suited for certain vegetative biophysical estimates and are more accurate or not otherwise obtainable by passive remote sensing systems. A number of studies have shown a significant relationship between L-Band SAR backscatter coefficients and forest structure parameters including above ground biomass and vegetative structural attributes. Other examples of terrestrial applications include wetland characterization, mapping, and monitoring and forest change analysis.

The Phased Array L-band Synthetic Aperture Radar (PALSAR) subsets provided in this data set might be useful for visual interest and preliminary analysis of the field area. For in-depth analyses, such as biomass estimation, vegetation characterization, etc., users might have to download the lower level products from ASF.

Quantitatively Comparing Multi-Temporal Data

The data values in the image are Digital Numbers (DN) that can be used in the following equation to extract the Normalized Radar Cross Section (NRCS).

NRCS (dB) = 10*log10(<DNˆ2>) + CF

Where the Calibration Factor (CF) is a constant -83. 

The cross section parameter is useful to quantitatively compare multi-temporal data.

The figure shows locations of sites with SAR images and Table 1 lists the site, and its physical attributes.

Terrestrial Ecology – Data Description

Dataset Description:

  • SAR — synthetic aperture radar
  • 2007-2010
  • 42 sites in North and South America, and Greenland
  • Monitoring networks include FLUXNET, Ameriflux, LTER, and the Greenland Climate Network (GC-Net)
  • GeoTIFF format in Universal Transverse Mercator (UTM) projection and 15-meter resolution

Data File Information

Each scene is available in GeoTIFF format with a XML file containing metadata. A PDF document file is also available for each site and contains image-specific metadata, image analysts notes about channel assignments and colors, and a thumbnail of the SAR image. For sites with multiple images, only one thumbnail is included as images are quite similar in appearance.

Example PDF File:

Site Name: Baltimore Ecosystem Study (BES1)
GeoTIFF: Baltimore_Ecosystem_Study_20090728.tif
Imagery Date: 28-Jul-2009, 03:32:51
Location: Maryland
The SAR image has greens, pinks, blacks and some gray colors. By assigning the HH to the red and blue channels
and the HV polarization to the green, we get these slightly more intuitive colors. Green is tree canopy. Black is water.
Polarization: FBD 34.3 HH+HV
Bands: HH (red and blue)
Bands: HV (green)

Spatial Coverage

The figure shows locations of sites with SAR images and Table 1 lists the site, and its physical attributes.

Sites: The figure shows locations of sites with SAR images and the following table lists the site, and its physical attributes.

Site Name Site Number Land Unit Latitude Longitude Site Type Vegetation type - IGBP Class
Arctic LTER (ARC1) 789 North America 68.62833 -149.593331 LTER Site Open shrublands
Baltimore Ecosystem Study (BES1) 945 North America 39.400281 -76.7702806 LTER Site Urban and built-up
Bartlett Experimental Forest 823 North America 44.06464 -71.2880769 Flux Tower Deciduous broad-leaf forest
BOREAS NSA — Old Black Spruce 234 North America 55.87962 -98.48081 Flux Tower Evergreen needle-leaf forest
BOREAS SSA — Young Aspen 285 North America 53.65601 -105.32314 Flux Tower Mixed forest
British Columbia — Campbell River — Clearcut Site 121 North America 49.87048 -125.29087 Flux Tower Evergreen needle-leaf forest
British Columbia — Campbell River — Mature Forest Site 120 North America 49.86725 -125.3336 Flux Tower Evergreen needle-leaf forest
Buffalo13 ESE — SDSU Antelope Research Station (Calving Pasture Site) 1060 North America 45.516 -103.3017 Climate reference network station Grasslands
Cascades/H.J. Andrews LTER — Oregon 809 North America 44.24885 -122.180347 Evergreen needle-leaf forest
Chamela Biological Station 644 North America 19.509281 -105.040175 Flux Tower Deciduous broad-leaf forest
CP1 2723 Europe 69.8819 -46.9736 GC-Net
Duke Forest Hardwoods 868 North America 35.973582 -79.1004304 Flux Tower Mixed forest
Harvard Forest EMS Tower (HFR1) 886 North America 42.537756 -72.1714778 Flux Tower Mixed forest
HJ Andrews Aeronet Sunphotometer (AND1) 1033 North America 44.238889 -122.223889 LTER Site Evergreen needle-leaf forest
Howland Forest (Main Tower) 890 North America 45.20407 -68.7402778 Flux Tower Mixed forest
Humboldt Gl. 2731 Europe 78.5266 -56.8305 GC-Net
Juniper Woodland Site 1050 North America 40.259322 -112.478125 Flux Tower Grassland
KULU 2738 Europe 65.7584 -39.6018 GC-Net
Lost Creek 931 North America 46.08268 -89.97919 Flux Tower Deciduous broad-leaf forest
Luquillo LTER (LUQ1) 681 North America 18.323889 -65.8175 LTER Site Evergreen broad-leaf forest
Metolius Eyerly Burn 954 North America 44.579442 -121.500076 Flux Tower Evergreen needle-leaf forest
Metolius Intermediate Pine 955 North America 44.452432 -121.557166 Flux Tower Evergreen needle-leaf forest
Missouri Ozark Site 967 North America 38.74411 -92.200009 Flux Tower Deciduous broad-leaf forest
NASA-E 2727 Europe 75 -29.9997 GC-Net
NGRIP 2729 Europe 75.0998 -42.3326 GC-Net
Niwot Ridge (LTER NWT1) 997 North America 40.032878 -105.546403 Flux Tower Evergreen needle-leaf forest
Park Falls 1036 North America 45.945878 -90.2723042 Flux Tower Deciduous broad-leaf forest
Phillips Creek Marsh (PHCK) 1091 North America 37.46069 -75.8347115 LTER Site Woody Savannas
Rond. — Faz. Nossa Senhora-Ji Parana — Pasture 71 South America -10.76181 -62.3572222 Flux Tower Savannas
Rond. — Rebio Jaru Ji Parana — Tower B 73 South America -10.07806 -61.9330972 Flux Tower Evergreen broad-leaf forest
Santarem — Km77 Pasture 84 South America -3.011896 -54.53652 Flux Tower Cropland/natural vegetation mosaic
Sask — SSA Old Aspen 258 North America 53.62889 -106.19779 Flux Tower Mixed forest
Sask — SSA Old Jack Pine 260 North America 53.91634 -104.69203 Flux Tower Evergreen needle-leaf forest
Sioux Falls Portable 2755 North America 43.2408 -96.902 Croplands
Sky Oaks 1067 North America 33.384444 -116.640261 Flux Tower Closed shrublands
Summit 2741 Europe 72.5794 -38.5042 GC-Net
Swiss Camp 2742 Europe 69.5732 -49.5952 GC-Net
Tablelands Juniper Savanna 2712 North America 34.425489 -105.861545 Open shrublands
Tonzi Ranch 1078 North America 38.4316 -120.965983 Flux Tower Woody savannas
Valles Caldera Mixed Conifer 2715 North America 35.888447 -106.532114 Woody savannas
Walker Branch Watershed 1096 North America 35.958767 -84.2874333 Flux Tower Deciduous broad-leaf forest
Western Peatland — LaBiche-Black Spruce/Larch Fen 292 North America 54.95384 -112.46698 Flux Tower Mixed forest

Collection boundaries: (All latitude and longitude given in decimal degrees)

Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
-156.6650 -29.9997 78.5266 -10.7618

Temporal Coverage

SAR subsets were extracted for the dates shown in the table below. The exact time of the image is included in the documentation. The selected sites, the name of their respective compressed image files, the date(s), and projections of the SAR subset image(s) are provided.

Site Name Site Number Image Date(s) Image Projection
Arctic LTER (ARC1) 789 2010/07/11 WGS84, UTM, Zone 6N
Baltimore Ecosystem Study (BES1) 945 2009/07/28 WGS84, UTM, Zone 18N
Bartlett Experimental Forest 823 2007/07/20, 2007/09/04, 2007/10/20, 2008/06/06, 2009/07/25, 2009/10/25, 2010/07/28, 2010/09/12, 2010/10/28 WGS84, UTM, Zone 19N
BOREAS NSA — Old Black Spruce 234 2010/09/24 WGS84, UTM, Zone 14N
BOREAS SSA — Young Aspen 285 2010/07/19 WGS84, UTM, Zone 13N
British Columbia — Campbell River — Clearcut Site 121 2010/06/05 WGS84, UTM, Zone 10N
British Columbia — Campbell River — Mature Forest Site 120 2010/06/05 WGS84, UTM, Zone 10N
Buffalo13 ESE — SDSU Antelope Research Station (Calving Pasture Site) 1060 2010/10/02 WGS84, UTM, Zone 13N
Cascades/H.J. Andrews LTER — Oregon 809 2008/10/25 WGS84, UTM, Zone 10N
Chamela Biological Station 644 2010/10/10 WGS84, UTM, Zone 13N
CP1 2723 2009/11/10 WGS84, UTM, Zone 23N
Duke Forest Hardwoods 868 2010/09/25 WGS84, UTM, Zone 17N
Harvard Forest EMS Tower (HFR1) 886 2007/08/23, 2010/08/31, 2010/10/16 WGS84, UTM, Zone 18N
HJ Andrews Aeronet Sunphotometer (AND1) 1033 2010/10/25 WGS84, UTM, Zone 10N
Howland Forest (Main Tower) 890 2010/10/18 WGS84, UTM, Zone 19N
Humboldt Gl. 2731 2010/06/29 WGS84, UTM, Zone 21N
Juniper Woodland Site 1050 2010/07/20 WGS84, UTM, Zone 12N
KULU 2738 2008/05/21, 2008/07/06, 2008/08/21 WGS84, UTM, Zone 24N
Lost Creek 931 2010/10/08 WGS84, UTM, Zone 15N
Luquillo LTER (LUQ1) 681 2010/10/11 WGS84, UTM, Zone 20N
Metolius Eyerly Burn 954 2010/06/29 WGS84, UTM, Zone 10N
Metolius Intermediate Pine 955 2010/06/29 WGS84, UTM, Zone 10N
Missouri Ozark Site 967 2010/08/04 WGS84, UTM, Zone 15N
NASA-E 2727 2009/12/23 WGS84, UTM, Zone 25N
NGRIP 2729 2010/06/29 WGS84, UTM, Zone 23N
Niwot Ridge (LTER NWT1) 997 2007/06/05, 2007/07/21, 2007/10/21, 2008/06/07, 2009/07/26, 2010/06/13, 2010/07/29, 2010/10/29, 2010/12/14 WGS84, UTM, Zone 13N
Park Falls 1036 2010/10/08 WGS84, UTM, Zone 15N
Phillips Creek Marsh (PHCK) 1091 2010/10/31 WGS84, UTM, Zone 18N
Rond. — Faz. Nossa Senhora-Ji Parana — Pasture 71 2010/10/21 WGS84, UTM, Zone 20S
Rond. — Rebio Jaru Ji Parana — Tower B 73 2010/07/17 WGS84, UTM, Zone 20S
Santarem — Km77 Pasture 84 2007/06/12, 2008/05/30, 2009/06/18, 2009/08/03, 2010/06/21, 2010/07/21, 2010/08/06, 2010/11/06 WGS84, UTM, Zone 21S
Sask — SSA Old Aspen 258 2010/11/05 WGS84, UTM, Zone 13N
Sask — SSA Old Jack Pine 260 2010/10/31 WGS84, UTM, Zone 13N
Sioux Falls Portable 2755 2010/03/20, 2010/06/29, 2010/07/16, 2010/08/31, 2010/10/16, 2010/12/01 WGS84, UTM, Zone 14N
Sky Oaks 1067 2009/11/18 WGS84, UTM, Zone 11N
Summit 2741 2010/01/23 WGS84, UTM, Zone 24N
Swiss Camp 2742 2010/01/05 WGS84, UTM, Zone 22N
Tablelands Juniper Savanna 2712 2010/09/18 WGS84, UTM, Zone 13N
Tonzi Ranch 1078 2010/09/17 WGS84, UTM, Zone 10N
Valles Caldera Mixed Conifer 2715 2010/10/05 WGS84, UTM, Zone 13N
Walker Branch Watershed 1096 2010/10/27 WGS84, UTM, Zone 16N
Western Peatland — LaBiche-Black Spruce/Larch Fen 292 2010/09/23 WGS84, UTM, Zone 12N