NASA SNF Project

Description

An inventory of NASA's airborne and field campaigns for Earth Science

SNF_ASP_CVR_140

The purpose of the Superior National Forest (SNF) study was to improve our understanding of the relationship between remotely sensed observations and important biophysical parameters in the boreal forest. A key element of the experiment was the development of methodologies to measure forest stand characteristics to determine values of importance to both remote sensing and ecology. Parameters studied were biomass, leaf area index, above ground net primary productivity, bark area index and ground coverage by vegetation. Thirty two quaking aspen and thirty one black spruce sites were studied. For the aspen sites, in each plot a visual estimation of the percent coverage of the canopy, subcanopy and understory vegetation was made. The site averages of these coverage estimates are presented in this data set.

SNF_BIOMASS_141

The purpose of the SNF study was to improve our understanding of the relationship between remotely sensed observations and important biophysical parameters in the boreal forest. A key element of the experiment was the development of methodologies to measure forest stand characteristics to determine values of importance to both remote sensing and ecology. Parameters studied were biomass, leaf area index, above ground net primary productivity, bark area index and ground coverage by vegetation. Thirty two quaking aspen and thirty one black spruce sites were studied. Aspen is an early successional, shade intolerant species. Aspen stands are essentially even aged, and stand age appears to be the most significant difference among sites in determining stand density, average diameter, and biomass density. Biomass density was highest in stands of older, larger trees and decreased in younger stands with smaller, denser stems. Since all aspen stands had closed canopies, the inverse relationship between biomass density and stem density suggests a series of stands in various stages of self thinning. Biomass density and projected LAI were much more variable for spruce than aspen. Spruce LAI and biomass density have a tight, nearly linear relationship. Stand attributes are often determined by site characteristics. Net primary productivity was estimated from the average radial growth over five years measured from the segments cut from the boles and the terminal growth measured as the height increase of the tree. Allometric equations were used to find the height and radial increment as a function of crown height and diameter at breast height. Spruce used an additional parameter of stem density. The models were used to back project five years and determine biomass at that time. The change in biomass over that time was used to determine the productivity. Measurements of sacrificed trees were used to develop relationships between the biophysical parameters (biomass, leaf area index, bark area index and net primary productivity) and the measurements made at each site (diameter at breast height, tree height, crown depth and stem density). These relationships were then used to estimate biophysical characteristics for the aspen and spruce study sites that are provided in the Forest Biophysical Parameters (SNF) data set.

SNF_HELO_MMR_144

A major aspect of the ground data collection effort in the SNF during the summers of 1983 and 1984 was the acquisition of helicopter canopy reflectance measurements. Canopy measurements were made at numerous sites with a helicopter-mounted Barnes multiband radiometer (MMR). MMR data were collected on ten dates in 1983 and eight dates in 1984. An additional Barnes radiometer was used to make simultaneous reference panel measurements. The canopy reflectance was derived from the canopy and reference panel measurements. All canopy and reference panel measurements were made under clear sky conditions. A majority of the helicopter measurements were taken at nadir view, although some off-nadir view angle measurements were taken primarily over black spruce and aspen sites. The reflectance factor is the ratio of radiant flux of the canopy measurement to that of the reference or calibration panel. Another component to be considered is atmospheric scatter, especially for aircraft measurements taken at higher altitudes. The amount of atmospheric scattering can be determined by using reflectance measurements of water targets. Reflectance measurements over water targets are included for all acquisitions in 1983. No water target measurements were taken during the 1984 field campaign. The summarized MMR data for both years, 1983 and 1984, are included in this data set. Fields include site ID number, number of observations averaged, code for altitude of instrument above the canopy, the time at which observations begin, the time at which observations end, sun zenith angle, sun azimuth angle, and reflectance for each of the bands (with standard deviations included within parenthesis). All measurements were taken at nadir, except where otherwise indicated. In 1984, MMR data were collected using off nadir view angles to measure the bi-directional reflectance characteristics of the forests.

SNF_MET_1972_158

Weather data were collected by the National Weather Service in International Falls, Minnesota. International Falls is about 80 miles from the SNF, but the weather data is representative of the area. Total solar insolation measurements were made at Fall Lake Dam in Winton, Minn. by Prof. Donald Baker of the Department of Soil Science at the University of Minnesota, St. Paul. Insolation values were measured using a Yellow Springs solar cell calibrated against an Eppley Pyranometer.

SNF_LEAF_EXP_180

The purpose of the SNF study was to improve understanding of the relationship between remotely sensed observations and important biophysical parameters in the boreal forest. A key element of the experiment was the development of methodologies to measure forest stand characteristics to determine values of importance to both remote sensing and ecology. Parameters studied were biomass, leaf area index, above-ground net primary productivity, bark area index and ground coverage by vegetation. Thirty two quaking aspen and thirty one black spruce sites were studied. Sites were chosen in uniform stands of aspen or spruce. Use of multiple plots within each site allowed estimation of the importance of spatial variation in stand parameters. Deciduous vegetation undergoes dramatic changes over the seasonal cycle. The varying amount of green foliage in the canopy effects the transpiration and productivity of the forest. Measurements of changes in the canopy and subcanopy green foliage amount over the spring of 1984 have been made. From above the subcanopy, photographs of the aspen canopy were taken, pointing vertically up. The photographs were taken at two locations in sites 16 and 93 on several different days. Foliage coverage was determined by overlaying grids with 200 points onto the photos of the canopy. The number of points obscured by vegetation were counted. These counts were adjusted for the area of the branches, which had been determined by photos taken before leaf out. The number of foliage points were then scaled between zero, for no leaves, to one, for maximum coverage. Subcanopy leaf extension was measured for beaked hazelnut and mountain maple, the two most common understory shrubs. For selected branches on trees in sites 16 and 93, the length and width of all leaves were measured on several days. These measurements were used to calculate a total leaf area which was scaled between 0 and 1 as with the aspen. The aspen canopy measurements have been combined with the subcanopy measurements and are available in this data set (i.e., SNF Forest Phenology/Leaf Expansion Data). These measurements of leafout show that the subcanopy leaf expansion lags behind that of the canopy. Subcanopy leaf expansion only begins in earnest after the canopy has reached nearly full coverage.

SNF_LEAFCARY_183

Knowledge of the optical properties of the components of the forest canopy is important to the understanding of how plants interact with their environment and how this information may be used to determine vegetation characteristics using remote sensing. During the summers of 1983 and 1984, samples of the major components of the boreal forest canopy (needles, leaves, branches, moss, litter) were collected in the Superior National Forest (SNF) of Minnesota and sent to the Johnson Space Center (JSC). At JSC, the spectral reflectance and transmittance characteristics of the samples were determined for wavelengths between .35 and 2.1 micrometers using the Cary-14 radiometer. This report presents plots of these data as well as averages to the Thematic Mapper Simulator (TMS) bands. There were two main thrusts to the SNF optical properties study. The first was to collect the optical properties of many of the components of the boreal forest canopy. The second goal of the study was to investigate the variability of optical properties within a species. The results of these studies allow a comparison of the optical properties of a variety of different species and a measure of the variability within species. These data provide basic information necessary to model canopy reflectance patterns.

SNF_NS001_185

The NS001 Thematic Mapper Simulator (TMS) was flown on the NASA C-130 aircraft over the Superior National Forest study area. TMS data were collected and processed for three days: July 13 and August 6, 1983; and June 28, 1984. The TMS was a scanning radiometer with eight wavelength bands. Band 8 was a thermal band and not processed in this study. The C-130 flew a "crisscross" pattern over the SNF, which provided a variety of sun and view angles. The TMS data were processed to provide reflectance values of study sites. These data are useful in the analysis of the bi-directional reflectance function of forest canopies. The TMS radiance values were converted to reflectance using values for insolation, atmospheric transmittance, and path scattered radiance for the appropriate solar and view angles. No measurement of these values were made, so the LOWTRAN6 atmosphere model was used to generate them. Scattering contributions calculated from the path between the canopy and the sensor were subtracted from the sensor detected radiances and divided by the incident flux to generate reflectance factors. Corrected canopy reflectance values for three days are included in the data set. Standard spherical polar coordinates, with zero degree azimuth due north, are given. Errors in the determination of these angles are possible due to the lack of precise aircraft position. The sensor zenith angles were determined from the sensor scan angle and should be accurate to within a degree. The sensor azimuth angles were determined from plotting the center points of a nadir view camera on an air photo of the area and connecting them to determine the aircraft heading. Because of the errors in this method, view azimuth accuracy is probably no more than two to three degrees. Solar zenith and azimuth were determined computationally from the time at the beginning of each flight line and should be within a degree. Sites referred to as 0 and 99 in the tables are observations of water.

SNF_SAT_INV_186

The purpose of the SNF Study was to develop the techniques to make the link from biophysical measurements made on the ground to aircraft radiometric measurements and then to scale up to satellite observations. Therefore, satellite image data were acquired for the Superior National Forest study site. These data were selected from all the scenes available from Landsat 1 through 5 and SPOT platforms. Image data substantially contaminated by cloud cover or of poor radiometric quality was not acquired. Of the Landsat scenes, only one Thematic Mapper (TM) scene was acquired, the remainder were Multispectral Scanner (MSS) images. Some of the acquired image data had cloud cover in portions of the scene or other problems with the data. These problems and other comments about the images are summarized in the data set. This data set contains a listing of the scenes that passed inspection and were acquired and archived by Goddard Space Flight Center. Though these image data are no longer available from either the Goddard Space Flight Center or the ORNL DAAC, this data set has been included in the Superior National Forest data collection in order to document which satellite images were used during the project.

SNF_CJ_SITES_187

This data set documentation is currently in work. In the interim, an abstract of the entire Superior National Forest (SNF) data collection activity from which the SNF Site Characterization Data: C.Jarvis data set is a product is being provided. During the summers of 1983 and 1984, the National Aeronautics and Space Administration (NASA) conducted an intensive experiment in a portion of the Superior National Forest (SNF) near Ely, Minnesota, USA. The purpose of the experiment was to investigate the ability of remote sensing to provide estimates of biophysical properties of ecosystems, such as leaf area index (LAI), biomass and net primary productivity (NPP). The study area covered a 50 x 50 km area centered at approximately 48 degrees North latitude and 92 degrees West longitude in northeastern Minnesota at the southern edge of the North American boreal forest. The SNF is mostly covered by boreal forest. Boreal forests were chosen for this project because of their relative taxonomic simplicity, their great extent, and their potential sensitivity to climatic change. Satellite, aircraft, helicopter and ground observations were obtained for the study area. These data comprise a unique dataset for the investigation of the relationships between the radiometric and biophysical properties of vegetated canopies. This is perhaps the most complete dataset of its type ever collected over a forested region. A key goal of the experiment was to use the aircraft measurements to scale up to satellite observations for the remote sensing of biophysical parameters.

SNF_SITE_86_188

This data set documentation is currently in work. In the interim, an abstract of the entire Superior National Forest (SNF) data collection activity from which the SNF Site Characterization Validation Data Set is a product is being provided. During the summers of 1983 and 1984, the National Aeronautics and Space Administration (NASA) conducted an intensive experiment in a portion of the Superior National Forest (SNF) near Ely, Minnesota, USA. The purpose of the experiment was to investigate the ability of remote sensing to provide estimates of biophysical properties of ecosystems, such as leaf area index (LAI), biomass and net primary productivity (NPP). The study area covered a 50 x 50 km area centered at approximately 48 degrees North latitude and 92 degrees West longitude in northeastern Minnesota at the southern edge of the North American boreal forest. The SNF is mostly covered by boreal forest. Boreal forests were chosen for this project because of their relative taxonomic simplicity, their great extent, and their potential sensitivity to climatic change. Satellite, aircraft, helicopter and ground observations were obtained for the study area. These data comprise a unique dataset for the investigation of the relationships between the radiometric and biophysical properties of vegetated canopies. This is perhaps the most complete dataset of its type ever collected over a forested region. A key goal of the experiment was to use the aircraft measurements to scale up to satellite observations for the remote sensing of biophysical parameters.

SNF_CJ_VEG_189

This data set documentation is currently in work. In the interim, an abstract of the entire Superior National Forest (SNF) data collection activity from which the SNF Vegetation Cover Data: C. Jarvis Data Set is a product is being provided. During the summers of 1983 and 1984, the National Aeronautics and Space Administration (NASA) conducted an intensive experiment in a portion of the Superior National Forest (SNF) near Ely, Minnesota, USA. The purpose of the experiment was to investigate the ability of remote sensing to provide estimates of biophysical properties of ecosystems, such as leaf area index (LAI), biomass and net primary productivity (NPP). The study area covered a 50 x 50 km area centered at approximately 48 degrees North latitude and 92 degrees West longitude in northeastern Minnesota at the southern edge of the North American boreal forest. The SNF is mostly covered by boreal forest. Boreal forests were chosen for this project because of their relative taxonomic simplicity, their great extent, and their potential sensitivity to climatic change. Satellite, aircraft, helicopter and ground observations were obtained for the study area. These data comprise a unique dataset for the investigation of the relationships between the radiometric and biophysical properties of vegetated canopies. This is perhaps the most complete dataset of its type ever collected over a forested region.

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https://impact.earthdata.nasa.gov/casei/campaign/SNF/

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NASA SNF Project was accessed on DATE from https://registry.opendata.aws/nasa-snf.