Airborne Imaging Systems Research Articles

Motion profile and control design of fast steering mirror for backscanning step and stare imaging.

Fast steering mirrors (FSMs) have been used for decades to improve the performance of electro-optical imaging systems, such as airborne imaging systems and space-based optical surveillance systems. With the advantage of increasing the accuracy of image motion compensation and the efficiency of scanning imaging, backscanning step-and-stare imaging has become the main approach to realizing wide-area surveillance for airborne imaging systems. According to the operating mode and motion profile of the FSM in the imaging system, a combined optimized profile (COP) is designed to avoid abrupt changes in the velocity and acceleration of the FSM. The angular position sensor based on a four-quadrant detector is used in FSMs to expand the measuring range and cut the cost at the expense of larger measurement noise. Combining a Kalman filter with a disturbance observer and zero-phase error tracking control, a control method is proposed to improve the control precision and bandwidth while suppressing measurement noise. Simulation and experimental results show that the profile designed by COP is smooth enough to meet the special requirements of FSM's backscanning image motion compensation and that the Kalman filter-based FSM control method can significantly improve the control accuracy.

Improving airborne far-field ultrasound acoustic imaging systems using high-K acoustic metamaterial

Airborne far-field ultrasound acoustic imaging systems allow scanning a large area that light-based imaging systems fail, such as glass walls and smoky environments. To scan the environment with great details, High-frequency acoustic waves should be used, but high-frequency waves attenuate fast, and it leads to low-range imaging. To address this challenge, a high-k acoustic metamaterial is used. This metamaterial is constructed of a subwavelength sequence of air-material layers and compresses the wave in a way that sound pressure increase in a particular frequency. In this research, a Uniform Linear Array consists of 30 microphones that designed to get a real-time 2-D image of the environment. Using this metamaterial increases the imaging range from 6 m to 15 m. It also improves the capability of the system to recognize small obstacles. By using the metamaterial array, an obstacle with a diameter of 1 cm is visible at a distance of 6 m while the smallest recognizable obstacle for the microphone array at the same distance has the diameter of 6 cm. The effect of the obstacle size and distance on image amplitude has been investigated and compensated. It is concluded that using metamaterials do not only increase the signal to noise ratio but also increase the quality of the image of a complex environment which consists of obstacles with different diameters.Airborne far-field ultrasound acoustic imaging systems allow scanning a large area that light-based imaging systems fail, such as glass walls and smoky environments. To scan the environment with great details, High-frequency acoustic waves should be used, but high-frequency waves attenuate fast, and it leads to low-range imaging. To address this challenge, a high-k acoustic metamaterial is used. This metamaterial is constructed of a subwavelength sequence of air-material layers and compresses the wave in a way that sound pressure increase in a particular frequency. In this research, a Uniform Linear Array consists of 30 microphones that designed to get a real-time 2-D image of the environment. Using this metamaterial increases the imaging range from 6 m to 15 m. It also improves the capability of the system to recognize small obstacles. By using the metamaterial array, an obstacle with a diameter of 1 cm is visible at a distance of 6 m while the smallest recognizable obstacle for the microphone array at t...

Integration of Aerial Imaging and Variable-Rate Technology for Site-Specific Aerial Herbicide Application

Abstract. As remote sensing and variable-rate technology are becoming more available for aerial applicators, practical methodologies for effective integration of these technologies are needed for site-specific aerial applications of crop production and protection materials. The objectives of this study were to demonstrate how to integrate an airborne multispectral imaging system and an IntelliStar variable-rate aerial application system for site-specific management of the winter weed henbit. The airborne imaging system was used to acquire natural color and near-infrared (NIR) images of a fallow field near College Station, Texas, for mapping the infestation of henbit shortly before herbicide application. The images were then rectified, classified, and converted to a binary prescription map with the full application rate on infested areas and the zero rate on non-infested areas. The variable-rate aerial application system mounted on an agricultural aircraft was used to apply glyphosate over the field based on the prescription map. Airborne imagery was collected 14 days after the herbicide application. The as-applied map along with the prescription map and the post-application imagery were used to assess the performance of the site-specific application. Spatial and statistical analysis results showed that the imaging system was effective for mapping henbit infestations and for assessing the performance of site-specific herbicide application, and that the variable-rate system accurately delivered the product at the desired rate to the prescribed areas for effective control of the weed. The methodology and results from this study will be useful for aerial applicators to incorporate airborne imaging and variable-rate application systems into their aerial application business to increase their capabilities and profits. Keywords: Aerial application, As-applied map, Henbit, Imaging system, Prescription map, Variable-rate technology.

Comparison of mosaicking techniques for airborne images from consumer-grade cameras

Images captured from airborne imaging systems can be mosaicked for diverse remote sensing applications. The objective of this study was to identify appropriate mosaicking techniques and software to generate mosaicked images for use by aerial applicators and other users. Three software packages—Photoshop CC, Autostitch, and Pix4Dmapper—were selected for mosaicking airborne images acquired from a large cropping area. Ground control points were collected for georeferencing the mosaicked images and for evaluating the accuracy of eight mosaicking techniques. Analysis and accuracy assessment showed that Pix4Dmapper can be the first choice if georeferenced imagery with high accuracy is required. The spherical method in Photoshop CC can be an alternative for cost considerations, and Autostitch can be used to quickly mosaic images with reduced spatial resolution. The results also showed that the accuracy of image mosaicking techniques could be greatly affected by the size of the imaging area or the number of the images and that the accuracy would be higher for a small area than for a large area. The results from this study will provide useful information for the selection of image mosaicking software and techniques for aerial applicators and other users.

OVERVIEW OF REMOTE SENSING APPLICATION FOR SEARCH OF MH370

This paper summarizes some remote sensing technologies in use by different search and rescue operators for the search of the missing Malaysia Airline (MH370). Studies are on-going using detected products and complex imagery. Some of the detected imagery currently does not provide reliable information, though the techniques themselves are promising. The introduction of microwave remote sensing systems will provide the much needed assistance when both visual searches and optical imaging systems do not help. However, under normal atmospheric conditions, airborne or space borne imaging systems are developed to obtain further information. The paper looked into the airplanes, flight data recorder and cockpit voice recorder, as well as the possible path.

Low-cost single-camera imaging system for aerial applicators

Agricultural aircraft provide a readily available and versatile platform for airborne remote sensing. Although various airborne imaging systems are available, most of these systems are either too expensive or too complex to be of practical use for day-to-day aerial application operations. The objective of this study was to develop a low-cost, user-friendly imaging system that can be easily installed on aerial applicators. An imaging system was assembled using off-the-shelf electronics. The system consisted of a digital camera to capture color images, a GPS receiver to geotag images, a video monitor to view live images, and a remote control to trigger the camera. The camera was attached to an aerial applicator and the GPS unit and video monitor were installed in the cockpit. The parameters of the camera were optimized to acquire images under various altitudes, speeds, and ground cover conditions. Geotagged images taken from individual sites or large areas were viewed and mosaicked together using free and inexpensive software. Aerial applicators can assemble such a system and use it to generate additional revenues from remote sensing services. Analysis of sample images has shown that the imaging system has potential for crop condition assessment and pest detection.

Airborne Spectral Polarimeter for Ocean Wave Research

AbstractThe Airborne Remote Optical Spotlight System (AROSS) family of sensors consists of airborne imaging systems that provide passive, high-dynamic range, time series image data and has been used successfully to characterize currents and bathymetry of nearshore ocean, tidal flat, and riverine environments. AROSS–multispectral polarimeter (AROSS-MSP) is a 12-camera system that extends this time series capability to simultaneous color and polarization measurements for the full linear polarization of the imaged scene in red, green, and blue, and near-infrared (RGB–NIR) wavelength bands. Color and polarimetry provide unique information for retrieving dynamic environmental parameters over a larger area (square kilometers) than is possible with typical in situ measurements. This particular field of optical remote sensing is developing rapidly, and simultaneous color and polarimetric data are expected to enable the development of a number of additional important environmental data products, such as the improved ability to image the subsurface water column or maximizing wave contrast to improve oceanographic parameter retrievals of wave spectra and wave heights.One of the main obstacles to providing good-quality polarimetric image data from a multicamera system is the ability to accurately merge imagery from the cameras to a subpixel level. This study shows that the imagery from AROSS-MSP can be merged to an accuracy better than one-twentieth of a pixel, comparing two different automated algorithmic techniques. This paper describes the architecture of AROSS-MSP, the approach for providing simultaneous color and polarization imagery in space and time, an error analysis to characterize the measurements, and example color and polarization data products from ocean wave imagery.

NEW LIGHT-WEIGHT STEREOSOPIC SPECTROMETRIC AIRBORNE IMAGING TECHNOLOGY FOR HIGH-RESOLUTION ENVIRONMENTAL REMOTE SENSING – CASE STUDIES IN WATER QUALITY MAPPING

Abstract. A new Fabry-Perot interferometer (FPI) based light-weight spectrometric camera provides new possibilities for environmental remote sensing applications. The sensor collects spectral data cubes with adjustable spectral properties in a rectangular image format, and so stereoscopic data can be obtained by gathering images in block structures with overlapping images. The FPI camera thus enables stereoscopic, spectrometric remote sensing applications with light-weight, low-cost airborne imaging systems. Our objective is to investigate the processing and use of this new imaging technology in a water quality mapping. We carried out imaging campaigns over a small lake in summer and autumn 2012 using a light-weight unmanned airborne vehicle (UAV) and a small manned airborne vehicle (MAV). We present the preliminary results of these campaigns.

Efficient method for the determination of image correspondence in airborne applications using inertial sensors

This paper presents a computationally efficient method for the measurement of a dense image correspondence vector field using supplementary data from an inertial navigation sensor (INS). The application is suited to airborne imaging systems, such as an unmanned air vehicle, where size, weight, and power restrictions limit the amount of onboard processing available. The limited processing will typically exclude the use of traditional, but computationally expensive, optical flow and block matching algorithms, such as Lucas-Kanade, Horn-Schunck, or the adaptive rood pattern search. Alternatively, the measurements obtained from an INS, on board the platform, lead to a closed-form solution to the correspondence field. Airborne platforms are well suited to this application because they already possess INSs and global positioning systems as part of their existing avionics package. We derive the closed-form solution for the image correspondence vector field based on the INS data. We then show, through both simulations and real flight data, that the closed-form inertial sensor solution outperforms traditional optical flow and block matching methods.

Bar 타겟을 이용한 DMC 영상의 공간해상력 검증

Today, a digital airborne imaging sensor plays an important role in construction of the numerous National Spatial Data Infrastructure. However, an appropriate quality assesment procedure for the acquired digital images should be preceded to make them useful data with high precision and reliability. A lot of studies therefore have been conducted in attempt to assess quality of digital images at home and abroad. In this regard, many test fields have been already established and operated to calibrate digital photogrammetric airborne imaging systems in Europe and America. These test fields contain not only GCPs(Ground Control Points) to test geometric performance of a digital camera but also various types of targets to evaluate its spatial and radiometric resolution. The purpose of this paper is to present a method to verify the spatial resolution of the Intergraph DMC digital camera and its results based on an experimental field testing. In field test, a simple bar target to be easily identified in image is used to check the spatial resolution. Images, theoretically designed to 12cm GSD(Ground Sample Distance), were used to calculate the actual resolution for all sub-images and virtual images in flight direction as well as in cross flight direction. The results showed that the actual image resolution was about 0.6cm worse than theoretically expected resolution. In addition, the greatest difference of 1.5cm between them was found in the image of block edge.

Analysis of Properties of Reflectance Reference Targets for Permanent Radiometric Test Sites of High Resolution Airborne Imaging Systems

Reliable and optimal exploitation of rapidly developing airborne imaging methods requires geometric and radiometric quality assurance of production systems in operational conditions. Permanent test sites are the most promising approach for cost-efficient performance assessment. Optimal construction of permanent radiometric test sites for high resolution airborne imaging systems is an unresolved issue. The objective of this study was to assess the performance of commercially available gravels and painted and unpainted concrete targets for permanent, open-air radiometric test sites under sub-optimal climate conditions in Southern Finland. The reflectance spectrum and reflectance anisotropy and their stability were characterized during the summer of 2009. The management of reflectance anisotropy and stability were shown to be the key issues for better than 5% reflectance accuracy.

PICASSO: an end-to-end image simulation tool for space and airborne imaging systems

The design of any modern imaging system is the end result of many trade studies, each seeking to optimize image quality within real world constraints such as cost, schedule and overall risk. Image chain analysis - the prediction of image quality from fundamental design parameters - is an important part of this design process. At The Aerospace Corporation we have been using a variety of image chain analysis tools for many years, the Parameterized Image Chain Analysis & Simulation SOftware (PICASSO) among them. In this paper we describe our PICASSO tool, showing how, starting with a high quality input image and hypothetical design descriptions representative of the current state of the art in commercial imaging satellites, PICASSO can generate standard metrics of image quality in support of the decision processes of designers and program managers alike.