This paper presents the results obtained from a maximally passive technique of obstacle detection for ground-based vehicles and rotorcraft. Automatic detection of these obstacles and the necessary guidance and control actions triggered by such detection would facilitate autonomous vehicle navigation. The approach to obstacle detection that is presented in this paper employs motion analysis of imagery generated by a passive sensor. Motion analysis of imagery obtained during vehicle travel is used to generate range measurements to world points within the field of view of the sensor, which can then be used to provide obstacle detection. Many types of existing vehicles contain an inertial navigation system (INS) which can be utilized to greatly improve the performance of motion analysis techniques and make them useful for practical military and civilian applications. Our motion analysis approach makes use of INS data to improve interest point selection, matching of the interest points, and the subsequent motion detection, tracking, and obstacle detection. In this paper we concentrate on the results of our processing when applied to sequences of lab and outdoor imagery. The range measurements that are made by INS integrated motion analysis are compared to a limited amount of ground truth that is available.

National attention has focused on the critical problem of detecting and avoiding windshear since the crash on August 2, 1985, of a Lockheed L-1011 at Dallas/Fort Worth International Airport. As part of The NASA/FAA National Integrated Windshear Program, we have defined a measurable windshear hazard index that can be remotely sensed from an aircraft, to give the pilot information about the wind conditions he will experience at some later time if he continues along the present flight path. Our technology analysis and end-to-end performance simulation, which measured signal-to-noise ratios and resulting wind velocity errors for competing coherent lidar systems, showed that a Ho:YAG lidar at a wavelength of 2.1 μm and a CO₂ lidar at 10.6 m can give the pilot information about the line-of-sight component of a windshear threat in a region extending from his present position to 2 to 4 km in front of the aircraft. This constitutes a warning time of 20 to 40 s, even under conditions of moderately heavy precipitation. Using these results, a Coherent Lidar Airborne Shear Sensor (CLASS), using a Q-switched CO₂ laser at 10.6 μm, is being designed and developed for flight evaluation in early 1992. The edge technique is a powerful new method for the measurement of small frequency shifts which allows high accuracy measurement of atmospheric winds (0.2 to 1 m/sec) with high vertical resolution (10 meters) using currently available technology.

Using navigational data, algorithms are defined for atmospheric absorption compensation by range dependent contrast enhancement, debanding by sensor response equalisation, and signal to noise enhancement by summation of image sub-sequences. Improved signal to noise is demonstrated by application to time sequences of infra-red images. Registration accuracy is examined as a function of range.

While performing the photo interpretation task using very high resolution images, the resolution of the image is often reduced to make its processing feasible. However, in low resolution images, it becomes quite difficult to segment and locate targets of interest such as aircraft, which are relatively small. Further, in recognizing aircraft, it is generally assumed that aircraft are already located. The emphasis is placed on model matching for recognizing isolated aircraft. However, locating potential areas in the images, where aircraft may be found, is non-trivial since it requires an accurate labeling of an image. We have developed a Knowledge-Based Photo Interpretation (KBPI) system that analyzes high resolution images. This system locates aircraft by first finding large structures in low resolution images and focusing attention on areas such as tarmacs, runways, parking areas, that have high probability of containing aircraft. Higher resolution images of the regions that are the focus of attention are used in subsequent analysis. The system makes extensive use of contextual knowledge such as spatial and locational information about airport scenes. We show results using high resolution TV data.

A comparison between two flow visualization studies of two impinging axisymmetric circular jets issuing into still fluid, using two different experimental techniques, is described. In one case, LIF is used to visualize the flow structure, while smoke is used in the second. Quantitative information has been obtained from these visualized flow regimes using two different digital imaging systems. Results are presented for both the jet profile shapes and the rate at which the jet expands in the downstream direction and these compare favorably with data obtained using established anemometry techniques.

Fractal geometry receives recently increasing attention in analyzing natural scenes. The fractal dimension of a surface image has been used as segmentation feature, but since it is not sufficient to characterize important configurative texture characteristics, additional features are necessary. In this work we use a combination of fractal and non-fractal features to segment and classify natural textures.

This paper discusses the use of image processing techniques for monitoring the performance of a sealing ring for an aircraft actuator. Methods of processing the images of a deforming seal ring and the mathematical relations between the computer acquired Cartesian images to the axisymmetric ring geometry are presented. Some of the features which allow the accurate interpretation of the images are discussed. The results obtained show the deformation of a seal ring under a hydrodynamic environment that exists in the actuator.

In this paper an infrared single element two-dimensional acoustooptic processor using a crystal of tellurium will be described, that can process to return echos of each pulse to form the image of the terrain illuminated by the SAR in real-time. This highly compact processor is designed to maintain a range and azimuth resolution of 2 m, will operate with an acoustic bandwith of 200 MHz for an acoustic drive-power of only 1 watt at the optic wavelength of 5 μm and will reach a dynamic range of the order of 40dB determined by the Hg Cd Te CCD array. This processor will control range and azimuth sidelobes below 40 dB, in a minimum detector integration time of 200 ms to resolve a 5 Hz Doppler frequency.

The general design, main components, and applications of the SPOT satellite system are briefly discussed with emphasis on defence applications. With its 10-m resolution in panchromatic mode, SPOT-1, launched in 1986, is particularly valuable in the fields of detection and reconnaissance. The fineness of resolution is supplemented by thematic processing resources applicable to digital optronic data. The system's operating method offers, at minimum cost, a means of rapidly accessing a wide area, updating information, and renewing information through repeat imagery. The possiblity of obtaining stereopairs by viewing a given point from different angles (+/- 27 deg) allows 3D viewing.

As the number of remote sensing sensors and the volume of data they collect increase, it becomes more important that systems for the automatic analysis of images are developed. The MuSIP project has developed a proof-of-concept software demonstrator for the fusion and analysis of remotely sensed images within a knowledge-based environment. The target application is the monitoring of forestry using a test dataset comprising optical and radar images spanning a 12 year period. The image data will be supplemented by other spatial information including digital map and geographic data as available. The MuSIP system is being implemented on a SUN-4 workstation with selected low level algorithms accelerated by a transputer based processor. The first phase of the MuSIP project was a 2 year (30 man year) ESPRIT project completed in February 1991.

Results of a feasibility study aimed at the development of a high resolution imaging interferometer (HRII) using Fourier transform spectroscopy are reported. The proposed instrument has three spectral ranges: a visible and near infrared (VNIR) from 0.45 to 1.0 micron, a short wave infrared (SWIR) from 1.0 to 2.5 microns, and the optional thermal infrared (TIR) from 8.0 to 12.5 microns. The spatial resolution on ground is proposed to be 40 m for VNIR and SWIR, and 200 m for TIR; the weight of the instrument will be less than 150 kg. The main conclusion of the study is that Fourier transform spectroscopy is well suited for imaging spectroscopy in space instrumentation.

One of the most important tasks in computational vision is to determine the structure of a scene in terms of its three dimensional objects and their spatial relationships. Functions such as landmark recognition, scene analysis, context based target recognition, digital map to scene correlation, and motion path planning all depend on accurate determination of the three dimensional description of the scene. In this paper we investigate a technique for determining structure of a scene from motion, based on the analysis of planes that "slice" a spatio-temporal volume. This technique uses a sequence of two dimensional images and generates a set of lines (epipolar-planar lines) corresponding to the planar surfaces in the scene. This technique was then applied to a variety of simulated scenes, sensor position and sensor speeds and the feasibility of the technique was established. For the reacquisition of landmarks we used the outputs of the epipolar-planar lines and performed a matching between the stored landmarks and the observed scene in a joint two dimensional Hough transform domain. This method was shown to be robust and fast in deciding whether a landmark is reobserved by the sensor. The result of this approach have significance in many fields such as scene analysis, autonomous navigation and target tracking.

The Clouds and Earth's Radiant Energy System (CERES) scanning radiometer will determine the radiation budget of the Earth on a regional basis over a number of years. The error in the reconstructed field is used as a design criterion for selecting design parameters for the instrument. The reconstruction error is comprised of errors due to aliasing, blurring and radiance equivalent noise of the instrument, and can be evaluated in terms of the transfer function of the system.

This paper discusses apparent deficiencies of the reflection coefficient (R) for inhomogeneous media (IX) and single-mode nonuniform waveguides (NOW5) as used in current wave propagation theory for time-harmonic waves. A new formulation is proposed (Rn) which tracks energy transport spatially, unlike the classical Schelkunoff formulation (Re) which may not display, even approximately, this property. Although the paper is focused on electromagnetic waves, the new formulation is also applicable to acoustics and related wave types. The paper discusses why, after more than four decades of careful measurement and analysis, the deficiencies have apparently gone undetected.

From the reflectance spectra R( ), the absolute value R710 at 710 nm , the ratios G/R = R560/R660 and IR/R = 766' the position re of the inflection point at the red edge, and the chroniaticity point are derived. The photosynthetic system (PS) is characterized by the fluorescence induction kinetics which provides the parameters Rfd and V0 for the estimate of the potential photosynthetic capacity and the chlorophyll concentration, respectively. Measurements obtained from spruce, birch, oak, and poplar of different damage class and color show correlations between the reflectance-S and fluorescence-characteristics. The chroinaticity points provide a two-dimensional analysis which may improve the separation between affected and healthy trees.