William T. Lawrence

A Technique for Using Composite DMSP/OLS "City Lights"Satellite Data to Map Urban Area

Abstract A Tresholding technique was used to convert a prototype “city lights” data set from the National Oceanic and Atmospheric Administrations National Geophysical Data Center (NOAAINGDC) into a map of “urban areas” for the continental United States. Thresholding was required to adapt the Defense Meteorological Satellite Programs Operational Linescan System (DMSPIOLS)-based NGDC data set into an urban map because the values reported in the prototype represent a cumulative percentage lighted for each pixel extracted from hundreds of nighttime cloud screened orbits, rather than any suitable land-cover classification. The cumulative percentage lighted data could not be used alone because the very high gain of the OLS nighttime photomultiplier configuration can. lead to a pixel (2.7X2.7 km) appearing “lighted” even with very low intensity, nonurban light sources. We found that a threshold of %89% yielded the best results, removing ephemeral light sources and “blooming” of light onto water when adjacent to cities while still leaving the dense urban core intact. This approach gave very good results when compared with the urban areas as defined by the 1990 U. S. Census; the “urban” area from our analysis being only 5% less than that of the Census. The Census was also used to derive population.- and housing-density statistics for the continent-wide “city lights” analysis; these averaged 1033 persons/km 2 and 426 housing units/ king, respectively. The use of a nighttime sensor to determine the location and estimate the density of population based on light sources has proved feasible in this exploratory effort. However, issues concerning the use of census data as a benchmark for evaluating the accuracy of remotely sensed imagery are discussed, and potential improvements in the sensor regarding spatial resolution, instrument gain, and pointing accuracy are addressed.

Using nighttime DMSP/OLS images of city lights to estimate the impact of urban land use on soil resources in the United States

Abstract Nightime “city light” footprints derived from DMSP/OLS satellite images were merged with census data and a digital soils map in a continental-scale test of a remote sensing and geographic information system methodology for approximating the extent of built-up land and its potential impact on soil resources in the United States. Using image processing techniques and census data, we generated maps where the “city lights” class represented mean population densities of 947 persons km −2 and 392 housing units km −2 , areas clearly not available to agriculture. By our analysis, such “city lights” representing urban areas accounted for 2.7% of the surface area in the United States, an area approximately equal to the State of Minnesota or one half the size of California. Using the UN/FAO Fertility Capability Classification System to rank soils, results for the United States show that development appears to be following soil resources, with the better agricultural soils being the most urbanized. Some unique soil types appear to be on the verge of being entirely coopted by “urban sprawl.” Urban area figures derived from the DMSP/OLS imagery compare well to those derived from statistical sources. Further testing and refinement of the methodology remain but the technique shows promise for possible extension to global evaluations of urbanization, population and even global productivity.

The use of multisource satellite and geospatial data to study the effect of urbanization on primary productivity in the United States

Data from two different satellites, a digital land cover map, and digital census data were analyzed and combined in a geographic information system to study the effect of urbanization on photosynthetic productivity in the United States. Results show that urbanization can have a measurable but variable impact on the primary productivity of the land surface. Annual productivity can be reduced by as much as 20 days in some areas, but in resource limited regions, photosynthetic production can be enhanced by human activity. Overall, urban development reduces the productivity of the land surface, and those areas with the highest productivity are directly in the path of urban sprawl.

Energy and Carbon Acquisition

This chapter describes the patterns of energy and carbon acquisition in plants growing at Echo Valley in southern California and Fundo Santa Laura in central Chile. The pattern of temperature and light dependency of photosynthesis is presented and evaluated, and geographic variability is discussed. Resource-use efficiency in important species is compared. Also, the relationship between carbon acquisition and species abundance in the vegetation is considered.

Laser altimetry waveform measurement of vegetation canopy structure

A profiling airborne laser altimeter system operating at 1.06 /spl mu/m has been developed to provide rapid, direct measurement of vegetation canopy structure by digitization of the amplitude versus time history of return laser pulse energy. The resulting waveforms are a measure of the vertical distribution of reflecting elements within a single laser footprint, including foliage, branches and ground. Vegetation height can be extracted from the waveform data based on the time difference between first and last returns. The altimeter system was deployed to the Pacific Northwest in September, 1993 where 5 flight missions were conducted over a variety of vegetated terrains, yielding approximately 4,000 km of georeferenced waveform profiles. Analysis of data from the Gifford Pinchot National Forest (GPNF) demonstrate good agreement between waveform-derived and ground-based measurements of vegetation height. The GPNF is a region of extensive timber harvesting, providing homogeneous areas of clear-cut, replanted conifers of increasing maturity, and old growth stands. Ground observations of canopy height and closure are available for 14 calibration stands that were differentiated, based on Landsat Thematic Mapper spectral characteristics, into 7 classes. Laser altimeter waveform data with a vertical sampling resolution of 22 cm were collected over calibration stands for 5 of the spectral classes. Last return pulses consistent with a ground measurement were acquired on every laser shot. Tree heights recovered from the altimeter waveforms show sub-meter agreement with ground based measurements, with essentially no vegetation cover on the clear cuts increasing to a mean tree height of 13 m on the most mature replanted sites. Altimeter-based tree heights for the old-growth stands typically range between 30 and 45 m, consistent with the ground measurements.<<ETX>>

BioSAR/sup TM/: an inexpensive airborne VHF multiband SAR system for vegetation biomass measurement

A pulse coherent synthetic aperture radar (SAR) operating between 80-120 MHz has been developed in an attempt to measure heavy forest biomass. The sensor uses a nadir-pointing antenna configuration and collects data in a 300-m wide swath on the ground along the flight line.

Relationships between soil properties and vegetation at the Northern Experimental Forest, Howland, Maine

Abstract This research relates the results of a survey and detailed analysis of soils in a northern mixed conifer forest to vegetation characteristics as represented by remotely sensed data. The work was conducted at International Papers Northern Experimental Forest (NEF) at Howland, Maine as part of NASAs Forest Ecosystem Dynamics (FED) project. An intensive soil survey was performed and relationships between soil properties (i.e., drainage class, depth of active zone, water holding capacity, carbon / nitrogen ratio, pH, and sum of bases), species composition, and normalized difference vegetation index (NDVI) from the Advanced Visible and Infrared Imaging Spectrometer (AVIRIS) were derived. Results showed that there was great variability in soil properties across the landscape due to complex regional glacial activity and recent alluvial events. Significant statistical differences were observed in species composition and NDVI between soil mapping units and with soil drainage class. However, other specific soil properties could not be used to explain these differences given the number of soil samples characterized, or without taking disturbance and management history into account. Simulation modeling, which would include soil data and stand history information as inputs, would provide an additional means of interpreting the relationship between remotely sensed imagery, inferred ecosystem properties, and complex, landscape-level patterns of soil characteristics.

Quantifying urban land use and impact on soils in Egypt using diurnal satellite imagery of the earth surface

Conversion of agricultural land to urban use represents a potential loss of agricultural productivity, especially in areas where arable land is in short supply. Using derived products from both daytime (Landsat sensor data) and night-time imaging systems (U.S. Air Force Defense Meteorological Satellite Programs Operational Linescan System (DMSP/OLS)) we examined the impacts of urbanization on soils in Egypt; a country with very limited agricultural land. We concluded that urban land cover types to occupy 3.7% of the total area of Egypt and that over 30% of the soils most suitable for agriculture are under urban land cover. Analysis of multiyear historical DMSP/OLS data sets (digitized from paper images) proved unreliable for long-term urban growth estimates.

Carbon Allocation and Utilization

This chapter describes the patterns of carbon metabolism and utilization in plants from southern California and central Chile. Rates of dark respiration and total carbon cost of leaves, stems, and roots are presented and compared. Growth and maintenance respiration rates for roots are presented, as is the effect of light on net carbon dioxide evoluation by stems. Allocation of carbon to various organic chemical fractions in leaves and stems is analyzed.

Comparative analysis of data acquired by three narrow-band airborne spectroradiometers over subboreal vegetation

Abstract Calibrated radiance data were acquired with three airborne sensor systems on 8 September 1990 over a northern forest as part of the Forest Ecosystem Dynamics Multisensor Aircraft Campaign. The spectral data were acquired nearly simultaneously under extremely clear sky conditions with NASAs AVIRIS and ASAS imaging spectroradiometers, and an SE-590 spectroradiometer mounted on a NASA UH-1B helicopter. After atmospheric corrections were applied to these data, intercomparisons of nadir reflectance factor measurements from each of these sensors were made for four important vegetation communities including a bog and individual forest stands dominated by spruce ( Picea sp.), eastern hemlock ( Tsuga canadensis ), and mixed northern hardwoods (dominated by Acer sp., Populus sp., and Betula sp.), respectively. The reflectance factor spectra from the different instruments were comparable for each of these cover types, suggesting the possible interchangeable use of the three datasets over comparable wavelength regions. These comparisons also serve to graphically illustrate the importance of applying atmospheric corrections to such data, even if acquired under extremely clear sky conditions. This remote sensing data set appears suitable for assessing the applicability of multistage, multisensor data in largescale ecological research.