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N.M. Milton

Publications and source records attributed to N.M. Milton.

13 recordsLinked to original sources
USGS2012

Discrimination of a chestnut-oak forest unit for geologic mapping by means of a principal component enhancement of Landsat multispectral scanner data

A principal component image enhancement has been effective in applying Landsat data to geologic mapping in a heavily forested area of eastern Virginia. A chestnut-oak forest unit, which occurs on metavolcanic rocks and some metaclastic rocks in the western Piedmont and on highly weathered upland gravel deposits in the eastern Piedmont, can be discerned on a digitally enhanced Landsat winter image. The image enhancement procedure consists of a principal component transformation, a histogram normalization, and the inverse principal component transformation. The enhancement preserves the independence of the principal components, yet produces a more readily interpretable image than does a single principal component transformation. To determine how the chestnut-oak forest unit was being enhanced, average Landsat multispectral scanner (MSS) values were extracted for four sample forest types and were calculated through the inverted principal component transformation. Slope and intercept values for the linear histogram normalization were chosen to keep the scale between the raw MSS bands and the inverted principal component (PC) bands constant. Plots of the inverted principal component data show that the most separation between forest types is in inverted PC band 5. The chestnut-oak forest unit is characterized by a high value for inverted PC band 5 as opposed to a low value for inverted PC band 4. In contrast, raw MSS band 4 is greater than MSS band 5 for the four forest types sampled in the winter image. Such observations cannot be readily deduced from analysis of only the principal component rotation matrix. They may ultimately provide a means to map the distribution of chestnut-oak forest from Landsat.

Geophysical Research Letters↗
USGS2012

Seasat synthetic aperture radar ( SAR) response to lowland vegetation types in eastern Maryland and Virginia

Examination of SEASAT SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the SCWigital number (DN) increase observed in the digital SEASAT data. The brightest areas in the Chickahominy, Virginia, drainage, containing P. virginica about 0.4 m high, contrast with the brightest areas in the Blackwater, Maryland, marshes, which contain mature loblolly pine in standing water. The darkest vegetated area in the Chickahominy drainage contains a forest of Nyssa aquatica (water tupelo) about 18 m high, while the darkest vegetated area in the Blackwater marshes contains the marsh plant Spartina alterniflora, 0.3 m high. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.

Journal of Geophysical Research - Oceans↗
USGS2007

Significance of non-isotropic scattering from vegetation for geobotanical remote sensing

Although it has been known for quite some time that individual leaves display non-Lambertian scattering at wavelengths of strong absorption in the visible part of the spectrum, while displaying near-Lambertian behaviour at wavelengths of little absorption in the near-infrared, this is widely ignored in geobotanical remote sensing investigations. Preliminary data show that non-Lambertian behaviour may have a significant effect on the ratio of infrared/red reflectance with changing illumination and observation angles, but little or no efTect on the location of the steep rise in reflectance from the red to the infrared (‘red edge’). These results indicate the need for a complete assessment of directional scattering from different vegetation and canopy types, and strongly suggest the need for caution in interpretation of observational data taken without regard for illumination and observation angles.

International Journal of Remote Sensing↗
USGS1991

Effect of phosphorus deficiency on spectral reflectance and morphology of soybean plants

Soybean plants were grown in hydroponic solutions having three concentration levels of phosphorus. Spectral reflectance changes included higher reflectance in the green and yellow portions of the electromagnetic spectrum in phosphorus-deficient plants and a difference in position of the long wavelength edge (the red edge) of the chlorophyll absorption band centered near 0.68 ??m. Plants having the least phosphorus in the growing medium did not show the normal shift of the red edge to longer wavelength which occurs as leaves mature. Shoot and root biomass were significantly lower in the phosphorus-deficient plants. These results are consistent with those obtained when soybean plants are dosed with elevated concentrations of metallic elements. We hypothesize that nutrient imbalances or anomalous metal concentrations in the soil set up physiological conditions at the soil/root interface that are responsible for the reflectance differences observed in laboratory and field studies of plants growing in substrates enriched in metallic elements.

Remote Sensing of Environment↗
USGS1989

Arsenic- and selenium-induced changes in spectral reflectance and morphology of soybean plants

Soybean (Glycine max) plants were grown in hydroponic solutions treated with high concentrations of either arsenic or selenium. Spectral reflectance changes in arsenic-dosed plants included a shift to shorter wavelengths in the long-wavelength edge of the chlorophyll absorption band centered at 680 nm (the red edge) and higher reflectance in the 550-650 nm region. These results are consistent with vegetation reflectance anomalies observed in previous greenhouse experiments and in airborne radiometer studies. The selenium-dosed plants contrast, exhibited a shift to longer wavelengths of the red edge and lower reflectance between 550 nm and 650 wh when compared with control plants. Morphological effects of arsenic uptake included lower overall biomass, stunted and discolored roots, and smaller leaves oriented more vertically than leaves of control plants. Selenium-dosed plants also displayed morphological changes, but root and leaf biomass were less affected than were those of arsenic-dosed plants when compared to control plants.

Remote Sensing of Environment↗
USGS1988

Thermal infrared (2.5- to 13.5-µm) directional hemispherical reflectance of leaves

Previous biconical reflectance measurements of 13 different plant species have shown that leaves display spectral signatures in the 8- to 14-??m atmospheric window that vary with species. Directional hemispherical reflectance measurements of six species reported here document the absolute magnitude of such spectral features for the first time. If half of the spectral contrast in leaf spectra is preserved in emittance from a broad-leaf planophile canopy, then at least some broad-leafed species could be mapped remotely by using currently available airborne instrumentation. -Authors

Photogrammetric Engineering and Remote Sensing↗
USGS1983

Remote detection of metal anomalies on Pilot Mountain, Randolph County, North Carolina

Pilot Mountain, a hydrothermally altered monadnock within the Carolina slate belt, contains areas of anomalously high amounts of Cu, Mo, and Sn in the soils. Leaves of canopy trees in the mineralized zone also contain more copper than trees in a nearby control area. Spectral data were processed using a wave-form analysis technique to minimize background noise caused by canopy variations and slope effects. Areas of spectral changes in the chlorophyll absorption region seem to correlate well with areas containing anomalous metals.

Economic Geology↗
USGS1982

Remote detection of metal anomalies on Pilot Mountain, Randolph County, North Carolina

A biogeophysical technique used successfully to delineate mineralized zones under coniferous forests has been extended to a deciduous region in the Piedmont physiographic province of North Carolina. Pilot Mountain, a hydrothermally altered monadnock within the Carolina slate belt, contains areas of anomalously high amounts of Cu, Mo, and Sn in the soils. Leaves of canopy trees in the mineralized zone also contain significant amounts of Cu. Spectral data acquired from a high-resolution airborne spectroradiometer were processed using a waveform analysis technique to minimize background noise caused by canopy variations and slope effects. Areas containing anomalous metals were detected by spectral changes in the chlorophyll absorption region.

Open-File Report↗