An integrated multisensor aircraft track recovery system for remote sensing

This paper describes an application of the Kalman filter in a track recovery system (TRS) for postflight processing of aircraft navigation sensor data. The track recovery system has been successfully used as a key component of the Canadian aerial hydrography pilot project for mapping of shallow coastal waters. Recorded data from an inertial navigation system (INS) is combined with data obtained from a number of auxiliary sensors to construct a set of error measurements. The measurements are prefiltered to compress the data and are then processed using aU-Dfactorized Kalman filter and a modified Bryson-Frazier smoother to produce estimates of the time-correlated sensor errors. The flight profile is obtained by subtracting the computed error estimates from the recorded INS data. The residual errors observed in processing real data collected in a number of field tests are less than 1 m in position and less than 0.03 degrees in attitude.     

An automatic region-based image segmentation algorithm for remote sensing applications

Object-based image analysis has proven its potentials for remote sensing applications, especially when using high-spatial resolution data. One of the first steps of object-based image analysis is to generate homogeneous regions from a pixel-based image, which is typically called the image segmentation process. This paper introduces a new automatic Region-based Image Segmentation Algorithm based on k-means clustering (RISA), specifically designed for remote sensing applications. The algorithm includes five steps: k-means clustering, segment initialization, seed generation, region growing, and region merging. RISA was evaluated using a case study focusing on land-cover classification for two sites: an agricultural area in the Republic of South Africa and a residential area in Fresno, CA. High spatial resolution SPOT 5 and QuickBird satellite imagery were used in the case study. RISA generated highly homogeneous regions based on visual inspection. The land-cover classification using the RISA-derived image segments resulted in higher accuracy than the classifications using the image segments derived from the Definiens software (eCognition) and original image pixels in combination with a minimum-distance classifier. Quantitative segmentation quality assessment using two object metrics showed RISA-derived segments successfully represented the reference objects.     

Airborne remote sensing from remotely piloted aircraft

Highly effective small-scale remote sensing can be carried out using a remotely piloted aircraft as a platform for various instruments. The operation of such a platform is described and details of two sensors (a photographic camera and a multiband radiometer)are given. Some preliminary results are presented and future developments are discussed.     

An evaluation of algorithms for the remote sensing of cyanobacterial biomass

Most remote sensing algorithms for phytoplankton in inland waters aim at the retrieval of the pigment chlorophyll a (Chl a), as this pigment is a useful proxy for phytoplankton biomass. More recently, algorithms have been developed to quantify the pigment phycocyanin (PC), which is characteristic of cyanobacteria, a phytoplankton group of relative importance to inland water management due to their negative impact on water quality in response to eutrophication.We evaluated the accuracy of three published algorithms for the remote sensing of PC in inland waters, using an extensive database of field radiometric and pigment data obtained in the Netherlands and Spain in the period 2001–2005. The three algorithms (a baseline, single band ratio, and a nested band ratio approach) all target the PC absorption effect observed in reflectance spectra in the 620 nm region. We evaluated the sensitivity of the algorithms to errors in reflectance measurements and investigated their performance in cyanobacteria-dominated water bodies as well as in the presence of other phytoplankton pigments.All algorithms performed best in moderate to high PC concentrations (50–200 mg m^? 3) and showed the most linear response to increasing PC in cyanobacteria-dominated waters. The highest errors showed at PC < 50 mg m^? 3. In eutrophic waters, the presence of other pigments explained a tendency to overestimate the PC concentration. In oligotrophic waters, negative PC predictions were observed. At very high concentrations (PC > 200 mg m^? 3), PC underestimations by the baseline and single band ratio algorithms were attributed to a non-linear relationship between PC and absorption in the 620 nm region. The nested band ratio gave the overall best fit between predicted and measured PC. For the Spanish dataset, a stable ratio of PC over cyanobacterial Chl a was observed, suggesting that PC is indeed a good proxy for cyanobacterial biomass. The single reflectance ratio was the only algorithm insensitive to changes in the amplitude of reflectance spectra, which were observed as a result of different measurement methodologies.     

UAVs surpassing satellites and aircraft in remote sensing over China

ABSTRACT

Many users are now showing strong interest in UAV RS (Unmanned Aerial Vehicle Remote Sensing) due to its easy accessibility. UAVs have become popular platforms for remote sensing data acquisition. In a number of practical and time constrained circumstances, UAV RS data have been widely used as a substitute for traditional satellite remote sensing data. However, airspace-related regulations are far behind the rapid growth in the number of UAVs and their wide applications. Much effort of the network-based UAV RS have been made by the UAV RS group of the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (IGSNRR, CAS), which proposed the concept of UAV RS data carrier. UAV RS data carrier refers to UAV RS data platform with task planning, data storage, image processing, product generation and output products for various UAVs. An ongoing effort to create a nationwide UAV RS network in addition to an existing ground observational network is being carried out in China.     

Small-scale aircraft detection in remote sensing images based on Faster-RCNN

Multimedia Tools and Applications - Detecting aircraft in remote sensing images becomes increasingly important in both military and civilian fields. However, the accuracy of existing detection...     

Fly-inspired visual steering of an ultralight indoor aircraft

We aim at developing autonomous microflyers capable of navigating within houses or small indoor environments using vision as the principal source of information. Due to severe weight and energy constraints, inspiration is taken from the fly for the selection of sensors, for signal processing, and for the control strategy. The current 30-g prototype is capable of autonomous steering in a 16/spl times/16 m textured environment. This paper describes models and algorithms which allow for efficient course stabilization and collision avoidance using optic flow and inertial information.     

Canopy spectral invariants for remote sensing and model applications

The concept of canopy spectral invariants expresses the observation that simple algebraic combinations of leaf and canopy spectral transmittance and reflectance become wavelength independent and determine a small set of canopy structure specific variables. This set includes the canopy interceptance, the recollision and the escape probabilities. These variables specify an accurate relationship between the spectral response of a vegetation canopy to the incident solar radiation at the leaf and the canopy scale and allow for a simple and accurate parameterization for the partitioning of the incoming radiation into canopy transmission, reflection and absorption at any wavelength in the solar spectrum. This paper presents a solid theoretical basis for spectral invariant relationships reported in literature with an emphasis on their accuracies in describing the shortwave radiative properties of the three-dimensional vegetation canopies. The analysis of data on leaf and canopy spectral transmittance and reflectance collected during the international field campaign in Flakaliden, Sweden, June 25-July 4, 2002 supports the proposed theory. The results presented here are essential to both modeling and remote sensing communities because they allow the separation of the structural and radiometric components of the measured/modeled signal. The canopy spectral invariants offer a simple and accurate parameterization for the shortwave radiation block in many global models of climate, hydrology, biogeochemistry, and ecology. In remote sensing applications, the information content of hyperspectral data can be fully exploited if the wavelength-independent variables can be retrieved, for they can be more directly related to structural characteristics of the three-dimensional vegetation canopy.     

Efficient radiative transfer model inversion for remote sensing applications

A simple method for efficient inversion of arbitrary radiative transfer models for image analysis is presented. The method operates by representing the shape of the function that maps model parameters to spectral reflectance by an adaptive look-up tree (ALUT) that evenly distributes the discretization error of tabulated reflectances in spectral space. A post-processing step organizes the data into a binary space partitioning tree that facilitates an efficient inversion search algorithm. In an example shallow water remote sensing application, the method performs faster than an implementation of previously published methodology and has the same accuracy in bathymetric retrievals. The method has no user configuration parameters requiring expert knowledge and minimizes the number of forward model runs required, making it highly suitable for routine operational implementation of image analysis methods. For the research community, straightforward and robust inversion allows research to focus on improving the radiative transfer models themselves without the added complication of devising an inversion strategy.     

A concurrent spectral-screening PCT algorithm for remote sensing applications

The paper presents a concurrent algorithm for remote sensing applications that provides significant performance and image quality enhancements over conventional uniprocessor principal component transform (PCT) techniques. The algorithm combines spectral angle classification, principal component transform, and human centered color mapping. It is evaluated from an image quality perspective using images collected with the hyper-spectral digital imagery collection experiment (HYDICE) sensor, an airborne imaging spectrometer. These images correspond to foliated scenes taken from an altitude of 2000–7500 m at wavelengths between 400 nm and 2.5 μm. The scenes contain mechanized vehicles sitting in open fields as well as under camouflage. The algorithm operates with close to linear speedup on shared memory multiprocessors and can be readily extended to operate on multiple, low-cost PC-style servers connected with high-performance networking. A simple analytical model is outlined that allows the impact on performance of practical, application-specific properties to be assessed. These properties include image resolution, number of spectral bands, increases in the number of processors, changes in processor technology, networking speeds and system clock rates.     

Spaceborne bistatic Synthetic Aperture Radar for remote sensing applications

This paper presents a performance analysis of spaceborne bistatic Synthetic Aperture Radar (SAR) for Earth observation. Since a bistatic system requires the simultaneous use of two spatially separated antennae, this paper refers to the European Space Agency ENVISAT-1 ASAR as the master mission, i.e. reflected echoes collected by ASAR are gathered also by a receiving-only slave antenna, which is on board a small satellite. Depending on orbit configuration, two mission profiles could be envisaged: two satellites flying along parallel orbits with different ascending nodes, or in one orbit plane with adequate angular separation. It is assumed that ENVISAT-1 is non-cooperative; therefore, signal synchronization and swath overlap and antenna separation control are committed to receiving-only spacecraft. To gain further insight into system geometric and radiometric characteristics and accuracy, several simulations are performed by using a computer code, which accounts for spacecraft orbit and attitude dynamics, sensor pointing geometry and Earth rotation. Numerical results and plots show the potentiality of the system for quite accurate three-dimensional measurements. In particular, thanks to system geometry, it is possible to compute target position and slant range components of velocity. Finally, further potential applications are outlined, also considering additional spin-offs for the master mission.     

Valve controlled fluorescence detection system for remote sensing applications

We demonstrate a microfluidics-based fluorescence detection device where the filters, source, detector, and electronically controlled valves are embedded into a Polydimethylsiloxane (PDMS)-based microfluidic chip. The device reported here has been specifically designed for chlorophyll a fluorescence sensing in autonomous systems, such as oceanic applications. In contrast to a monolithic approach, the modular approach made the fabrication of this device simpler and cheaper. For fluorescence detection, an InGaN/GaN LED is used as the excitation source to specifically excite chlorophyll a; a metal-dielectric Fabry?CPerot filter was used to extinguish out-of-band excitation. A simple Si photodiode is used as detector and provided with a thermally evaporated CdS emission filter to block the excitation source. This filter combination provides an excellent solution to the difficult problem of combining high-rejection excitation and emission filters in an integrated thin-film format. Furthermore, the metal-dielectric filter provides a much broader angular response than a comparable multilayer Bragg mirror, which is a key advantage in the integrated format. We use a novel paraffin wax-based valve design affords low power single-use actuation, between 0.5 and 1 J per actuation and withstands 0.6 bar differential pressure, which provides better performance than its previously reported counterparts. The remote valve-controlled operation of the fluorescence detection system is demonstrated, illustrating the measurement of a chlorophyll a solution, with a detection limit of 340 ??M and subsequent valve-controlled flushing of the measurement reservoir.     

Education and training for marine science applications of remote sensing

Abstract

An analysis is presented of the education and training programme whichis needed to provide the skilledmanpower required if oceanographicscience is to benefit fully from the marine remote sensing satellites due to be launched in the next decade. Education in satellite oceanography is treated distinctly from general remote sensing training, and it is argued that all oceanographers will, in future, need to be educated in this field. The required content of satellite oceanography training courses is reviewed in relation to the level of education desired and the background discipline of the trainees. Options for different teaching frameworks arc considered, including short courses or summer schools and distance learning for small groups. There is seen to be a high potential for adopting newteaching technologyin this field. Finally, somesuggestionsare made about the importance of including adequate training as an integral part of future ocean remote sensing programmes.     

Concurrent remote sensing of Arctic sea ice from submarine and aircraft

Abstract

In May 1987 a concurrent remote sensing study of Arctic sea ice from above and below was carried out. A submarine equipped with sidescan and upward looking sonar collaborated with two remote sensing aircraft equipped with passive microwave, synthetic aperture radar (SAR), a laser profilometer and an infrared radiometer. By careful registration of the three tracks it has been possible to find relationships between ice type, ice morphology and thickness, SAR backscatter and microwave brightness temperatures. The key to the process has been the sidescan sonar's ability to identify ice type through differences in characteristic topography. Over a heavily ridged area of mainly multiyear ice there is a strong positive correlation between SAR backscatter and ice draft or elevation. We also found that passive and active microwave complement each other in that SAR has a high contrast between open water and multiyear ice, while passive microwave has a high contrast between open water and first-year ice.     

Mapping applications for low-cost remote sensing and geographic information systems

Abstract

Increasing attention is being given to the practicability of remote sensing and geographic information systems (GIS). Easily adaptable low-cost systems in these two rapidly advancing technologies have particular relevance for developing nations. Data from advanced satellite sensor sytems such as the SPOT High Resolution Visible (HRV) and the Landsat Thematic Mapper (TM) have proven to be useful in topographic as well as thematic mapping, particularly for map revision. Based on the specific application, mapping systems have ranged from simple visual image interpretation lo automated digital image analysis systems with sophisticated classification schemes. Examples of topographic and thematic mapping using low-cost systems will be presented.

GIS have extended the capability of low-cost digital systems that simply provided storage and map production capabilities, to systems providing spatial data analysis including the linkage of spatial data and spatially related attributes. Data capture is an essential but laborious and expensive component of the overall mapping system. Satellite remote sensing is an obvious source of data for mapping and map revision because of its repetitive wide-area coverage and low cost. The need for integration of remote sensing and GIS is thus inevitable and is rapidly emerging because of the complementary role played by these technologies in resource management. The importance and utility of this integrated approach to mapping will be documented using Canadian examples.     

An integrated data system for airborne remote sensing

This paper outlines the rationale and design for an enhanced Airborne Remote Sensing (ARS) facility, being implemented by the Natural Environment Research Council (NERC) in the U.K., to support environmental research and monitoring. It is based on the provision of a suite of optical remote sensing instruments, available for year-round deployment, and the development of an on-board integrated data acquisition, and ground-based data processing, system. Acquisition of the remotely sensed data will be synchronized with attitude/position information from a global positioning satellite (GPS) system to enable an accurate geometric rectification to be performed. A strategy has been devised for the endto-end ground processing of this data to enable the production of standard data products and distribution in a sensor-independent data format. The facility has been fully operational from Spring 1997 and is ready to support the needs of environmental scientists and organizations requiring high quality, and immediately usable, airborne remotely sensed data products.     

An assessment of SPOT capability for cartographic applications in Indonesia

Abstract

An assessment of the operational cartographic capability of SPOT in Indonesia is presented from the points of view of (1) the size of the smallest distinguishable land cover units through computation of the percentages of pure pixels per unit and dominant unit per pixel and (2) planimetric accuracy. Generally speaking, units larger than 0.16 and 0.05ha can be distinguished with SPOT multispectral (XS) and panchromatic (P) data respectively. For full images, basic manipulations (bilinear transformation or shift, enlargement and rotation) of level-IB SPOT digital data and photographs provide standard deviation accuracies towards local Transverse Mercator (LTM) maps of 2 and 3 pixels, respectively. Due to the poor reliability of most LTM maps, SPOT should undoubtedly be used as a major cartographic data source in Indonesia.     

Assessing drought probability for agricultural areas in Africa with coarse resolution remote sensing imagery

Drought is one of the most frequent climate-related disasters occurring across large portions of the African continent, often with devastating consequences for the food security of agricultural households. This study proposes a novel method for calculating the empirical probability of having a significant proportion of the total agricultural area affected by drought at sub-national level. First, we used the per-pixel Vegetation Health Index (VHI) from the Advanced Very High Resolution Radiometer (AVHRR) averaged over the crop season as main drought indicator. A phenological model based on NDVI was employed for defining the start of season (SOS) and end of the grain filling stage (GFS) dates. Second, the per-pixel average VHI was aggregated for agricultural areas at sub-national level in order to obtain a drought intensity indicator. Seasonal VHI averaging according to the phenological model proved to be a valid drought indicator for the African continent, and is highly correlated with the drought events recorded during the period (1981-2009). The final results express the empirical probability of drought occurrence over both the temporal and the spatial domain, representing a promising tool for future drought monitoring.     

An overview of small satellites in remote sensing*

This article gives a global overview of some aspects of small satellite developments since the launch of Sputnik‐1 50 years ago. These developments are offering new opportunities for remote sensing.

The earliest satellites were small but, as time went on, the satellites that were flown were developed to serve several different projects and they became larger and more expensive and took a long time to design, build and be launched. One of the extreme examples was Envisat. For these large satellites compromises often had to be made between different objectives and different instruments. A failure of the whole system meant the death of many different projects.

The future is likely to see more small satellites, each of which is dedicated to a particular mission objective and carries a single instrument. Through this approach more and more countries around the world are becoming involved in Earth observation from space, not just in using the data from the major established systems but also in constructing their own systems.

There were some small, low‐cost satellites in the early days, but they were overlooked or considered toys by the space community. The first microsatellites were built by enthusiasts of the amateur radio community and launched in the early 1960s. The invention/introduction of the microprocessor in the 1970s represented a quantum jump for the onboard capabilities of a spacecraft. This technology introduction represented a prime catalyst in the development of microsatellites since it enabled small physical structures in support of sophisticated data handling applications. The engineering of microsatellites, which emerged in the early 1980s, took a radical change of approach from the custom design of traditional spacecraft, namely a design‐to‐capability scheme to achieve cost reductions by focusing on available, and existing technologies using a general purpose bus and ‘off‐the‐shelf’ components and instruments.

The new approach of small satellite design was pioneered by Surrey Satellite Technology Ltd (SSTL) of Surrey University, UK. SSTL's lead has now been followed by various companies and space agencies throughout the world. A key feature of this work is the development of microsatellite technology transfer programmes, providing partnerships and on‐the‐job training of engineers and scientists of foreign national organizations in cooperative programmes – in particular to those who were not in a position to start or afford their own space projects – to participate in the development of their own microsatellites.

In addition to discussing these developments, this article also covers small satellite classification, small satellite initiatives in the USA, small satellite development in the rest of the world, some aspects of the technology and applications of small satellites, and small satellites developed by universities, particularly the CubeSats programme.

Today, small satellites are changing the economics of space. These spacecraft embrace cutting edge Commercial Off‐The‐Shelf (COTS) technology, permitting novel and less‐expensive ways to perform meaningful observation missions, although there are various technical challenges. There are several synthetic aperture radar (SAR) and hyperspectral imaging missions on small satellites in operation and in planning.     

一种卫星遥感影像村庄区域提取算法

卫星遥感影像提取村庄区域在地理和气象领域均有十分重要的意义.针对卫星遥感影像的特点,提出了一种村庄区域提取方法.利用改进的去雾算法对卫星遥感影像进行预处理,通过遥感卫星影像的颜色特征实现分割,结合村庄区域分布特点进行去噪处理,实现卫星遥感影像村庄区域的提取.实验结果表明:该算法能够对卫星遥感图像中不同类型村庄区域进行提取,且提取准确率高,可以应用于地理以及气象等领域.