Airborne Video Imagery Research Articles

The Biological Flora of Coastal Dunes and Wetlands:Avicennia germinans(L.) L.

ABSTRACT Lonard, R.I.; Judd, F.W.; Summy, K.R.; DeYoe, H., and Stalter, R., 2017. The biological flora of coastal dunes and wetlands: Avicennia germinans (L.) L. Avicennia germinans (L.) L. is a pantropical, subtropical, and occasionally warm-temperate mangrove species that occurs on shorelines that have a broad horizontal tidal range. Also known as black mangrove, stands typically develop under anoxic, water-logged conditions in substrates of silt or clay. Black mangrove can tolerate salinity values ranging from 0 to 90 parts per thousand. Salt is excreted from salt glands on both leaf epidermal surfaces, and aerosol salt spray and salt crystals are frequently observed on the upper leaf epidermis. Avicennia germinans is viviparous. The embryos have no dormancy requirements, and there is no seed bank. This mangrove species has the northernmost distributional range of any mangrove species in North America. It occurs in Louisiana and northern Florida. Color-infrared photography and airborne video imagery te...

A multilayer feedforward neural network for automatic classification of eucalyptus forests in airborne video imagery

Eucalypt tree dieback is a disease that threatens the survival of woodlands in Australian national parks. For mapping and monitoring the spatial distribution of dieback, airborne imaging technologies can be more effective than ground surveys. Amongst the numerous types of airborne sensors, the video camera provides images with very high spatial resolution. In order to detect individual defoliated Eucalyptus trees at Mt Eccles national park (south‐western Victoria), aerial video data was acquired across the study site. Highlighting the health status of sparse and mainly unclustered defoliated eucalypts at Mt Eccles through video images was deemed to be achievable in several steps. This paper introduces a classification method based on a feedforward neural network, whose main goal is to perform a segmentation of the video frames into three classes, namely, bare branches or trunks, healthy canopy and understorey vegetation. The aim of the algorithm is to create a subset of the eucalypt tree group, including defoliated and dead trees, for further analysis. The results suggest that the recognition of trunks and systems of bare branches is feasible using the neural network architecture. This provides a means to pre‐process the video data so as to analyse the health of trees and thus assist park managers with managing dieback.

Short‐term changes in the plan shape of a sandy beach in response to sheltering by a nearshore mud bank, Cayenne, French Guiana

AbstractMontjoly is a headland‐bound embayed sandy beach in Cayenne, French Guiana, that shows long‐term plan shape equilibrium in spite of periodic changes in accretion and erosion that alternately affect either end of the beach. These changes are caused by mud banks that move alongshore from the Amazon. The mechanisms involved in changes in the plan shape of the beach in response to the passage of one of these mud banks were monitored between 1997 and 2000 from airborne video imagery and field work. The beach longshore drift to the northwest, driven by the incident easterly to northeasterly swell usually affecting this coast, became temporarily reversed as the mud bank, migrating from east to west, initially sheltered the southeastern end of the beach. The difference in exposure to waves engendered a negative wave height gradient alongshore towards the southeast, resulting in the setting up of a cell circulation and counter‐active longshore drift from the exposed northwestern sector to the southeast. Sand eroded from the exposed sector accumulated first in the southeastern, and then the central sectors of the beach. The effect of increasing beach sheltering by the mudbank moving west is highlighted on the videographs by an ‘arrested’ pattern of beach shoreline development. The videographs show hardly any changes in beach plan shape since January 1999, due to sheltering of the beach from wave attack by the mud bank. It is expected that the eroded sector will recover in the future as the mud bank passes, leading to re‐establishment of the northwesterly sand drift. This temporally phased bi‐directional drift within the confines of the bounding headlands results in a rare example of mud‐bank‐induced beach rotation, and probably explains the long‐term equilibrium plan shape of Montjoly beach. Copyright © 2002 John Wiley & Sons, Ltd.

A simplified method for retrieval of ground level reflectance of targets from airborne video imagery

This paper describes an efficient method for retrieval of ground reflectance characteristics of targets from calibrated multispectral airborne video data for routine operational airborne missions. The method uses a simplified atmospheric scattering model in combination with a dark-object subtraction procedure to estimate the effect of the atmosphere in the path between the target and the sensor, as well as the adjacent environmental effect, on the radiation signal received by an airborne sensor. The simplicity of the atmospheric scattering model is maintained by the assumption that the air density within the targetsensor path in the lower atmosphere is sufficiently uniform for operations of the Charles Sturt University's (CSU) Multispectral Airborne Video System (MAVS). The MAVS acquires imagery in blue, green, red and near-infrared (NIR) narrow spectral bands. The MAVS is radiometrically calibrated and has a consistent radiometric response in-flight. An important feature of the new method is the coupling of the image based brightness data (DN) of a dark-object and the system radiometric calibration coefficients to determine the path reflectance and the environmental reflectance of the target. The sum of the path reflectance and the environment reflectance is known as haze reflectance. The haze reflectance indicates the amount of atmospheric haze in the airborne imagery. The simplified atmospheric model is then employed to determine the actual ground reflectance of the targets using the haze subtracted apparent (total) reflectance of the target at the altitude of the airborne sensor. The apparent reflectance of the target at the sensor altitude is obtained directly from the image based DN data and the system radiometric calibration coefficients. An interesting aspect of this simplified method is that an estimate of the environmental reflectance can be obtained as a by-product of the atmospheric haze calculation using a dark-object subtraction technique. The retrieved ground reflectance characteristics from calibrated MAVS imagery are now being used routinely for remote quantitative monitoring of agricultural and environmental targets.

A simplified method for retrieval of ground level reflectance of targets from airborne video imagery

This paper describes an efficient method for retrieval of ground reflectance characteristics of targets from calibrated multispectral airborne video data for routine operational airborne missions. The method uses a simplified atmospheric scattering model in combination with a dark-object subtraction procedure to estimate the effect of the atmosphere in the path between the target and the sensor, as well as the adjacent environmental effect, on the radiation signal received by an airborne sensor. The simplicity of the atmospheric scattering model is maintained by the assumption that the air density within the targetsensor path in the lower atmosphere is sufficiently uniform for operations of the Charles Sturt University's (CSU) Multispectral Airborne Video System (MAVS). The MAVS acquires imagery in blue, green, red and near-infrared (NIR) narrow spectral bands. The MAVS is radiometrically calibrated and has a consistent radiometric response in-flight. An important feature of the new method is the coupling of the image based brightness data (DN) of a dark-object and the system radiometric calibration coefficients to determine the path reflectance and the environmental reflectance of the target. The sum of the path reflectance and the environment reflectance is known as haze reflectance. The haze reflectance indicates the amount of atmospheric haze in the airborne imagery. The simplified atmospheric model is then employed to determine the actual ground reflectance of the targets using the haze subtracted apparent (total) reflectance of the target at the altitude of the airborne sensor. The apparent reflectance of the target at the sensor altitude is obtained directly from the image based DN data and the system radiometric calibration coefficients. An interesting aspect of this simplified method is that an estimate of the environmental reflectance can be obtained as a by-product of the atmospheric haze calculation using a dark-object subtraction technique. The retrieved ground reflectance characteristics from calibrated MAVS imagery are now being used routinely for remote quantitative monitoring of agricultural and environmental targets.

Utilizing airborne video imagery in kenaf management and production

Kenaf ( Hibiscus cannabinus L.) is a rapid-growing nonwood fiber crop that can attain heights in excess of 5 m during a 150–200 day season. The tall kenaf coupled with the high plant densities used in commercial production can make visual detection of crop stress difficult. Airborne video imagery was evaluated for assessing kenaf production at three different locations. Results indicated that airborne video imagery had good potential for detecting crop stress resulting from Phymatotrichum root rot and the root-knot nematode/soil-borne fungi complex. Video imagery from all three locations indicated that remote sensing technology can provide an effective means for detecting and monitoring crop injury and disease movement in kenaf production. Airborne video imagery should be useful for detecting problem areas in large-scale plantings of kenaf. Identification of these potential problem areas should be beneficial to producers in regards to crop management.

Procedures for correcting high resolution airborne video imagery

Abstract Airborne videography is a useful way of producing very high resolution remotely-sensed data. Before video data can be used for digital analysis, individual frames must be correcled for geometric distortion and brightness variation. The most obvious geometric distortion occurs because the odd and even fields in a video frame are collected sequentially and can be displaced relative to each other by aircraft roll and forward motion. We describe a procedure for correcting this distortion based on the cross-correla lion between individual fields at different spatial lags. Brightness variation across frames occurs because of dilTerences in viewing geometry, bi-directional reflectance variation and atmospheric scattering. We describe a method for removing much of this variation by calculating scattering angle across the image with an optional adjustment for sensor plane tilt. Relations between scattering angle and scene brightness statistics may then be calculated from sequences of images collected alon...

Distinguishing Brush and Weeds on Rangelands Using Video Remote Sensing

This paper describes the application of a relatively new remote sensing tool, airborne video imagery, for distinguishing weed and brush species on rangelands. Plant species studied were false broomweed, spiny aster, and Chinese tamarisk. A multispectral video system that acquired color-infrared (CIR) composite imagery and its simultaneously synchronized three-band [near-infrared (NIR), red, and yellow-green] narrowband images was used for the false broomweed and spiny aster experiments. A conventional color camcorder video system was used to study Chinese tamarisk. False broomweed and spiny aster could be detected on CIR composite and NIR narrowband imagery, while Chinese tamarisk could be distinguished on conventional color imagery. Quantitative data obtained from digitized video images of the three species showed that their digital values were statistically different (P = 0.05) from those of associated vegetation and soil. Computer analyses of video images showed that populations of the three species could be quantified from associated vegetation. This technique permits area estimates of false broomweed, spiny aster, and Chinese tamarisk populations on rangeland and wildland areas.

Assessment of grassland phytomass with airborne video imagery

Airborne video imagery was evaluated for assessing phytomass production within grass plots fertilized with five rates of nitrogen. Video imagery was taken with two black-and-white video cameras—one visible light and the other visible/near-infrared light sensitive. Red (0.644–0.656-μm) and infrared (0.815–0.827-μm) narrowband filters were used with the visible and visible/near-infrared light sensitive cameras, respectively. Hand-held red and infrared radiometric reflectance and phytomass measurements were made on the day that imagery was obtained. Red and infrared digital video data were obtained from the plots using an image processor. The plots were studied on two dates: 15 April and 22 May 1985. On 15 April, three phytomass levels could be distinguished within the infrared video image. Moreover, a infrared/red ratio video composite produced on an image processor enhanced differences among nitrogen treatments to the extent that generally four levels of phytomass could be identified. Coefficients of determination ( r 2), obtained by regressing red, infrared, and infrared/red reflectance, and red, infrared, and infrared/red digital video data on phytomass measurements were significant statistically. Imagery acquired on 22 May, however, showed few differences among treatments. This may have been caused by plant phenological and canopy architectural differences among the grass species. Nevertheless, video imagery should be a useful tool to assess phytomass production on rangelands when grasses are actively growing.