Terrain Imagery Research Articles

Evaluating GOES-16 ABI surface brightness temperature observation biases over the central Sierra Nevada of California

Thermal infrared imagery from NOAA's Geostationary Operational Environmental Satellites (GOES) R-series presents an opportunity to observe mountain surface temperatures at high temporal resolution. These observations are needed to better understand the transient surface energy balance, influenced by near-surface air temperatures and water fluxes ranging from evapotranspiration to snowmelt. From geostationary orbit, the GOES Advanced Baseline Imager (ABI) instrument views the Earth from a fixed longitude above the equator. ABI images therefore have increasingly off-nadir view angles and increasingly larger pixel dimensions the further a point on the Earth's surface is from the sub-satellite point. In thermal infrared imagery from ABI, these 2+ km pixels blur together the different surface temperatures of heterogeneous mountain landscapes. We compared GOES-16 ABI band 14 (11.2 μm) brightness temperatures to 90 m spatial resolution ASTER band 14 (11.3 μm) and 1 km spatial resolution MODIS band 31 (11.03 μm) brightness temperatures and investigated how differences change over space and time for a study region in the central Sierra Nevada of California for the 2017–2020 snow seasons. We demonstrated the necessity of orthorectifying ABI imagery of mountain terrain to correct for the parallax effect in off-nadir imagery. This reduced the mean difference between ABI and ASTER ~11 μm brightness temperatures from 1.6 °C to 1.0 °C and increased the r-squared value between ABI and ASTER thermal infrared brightness temperatures from 0.43 to 0.93. The ABI brightness temperatures were found to more closely match those of forest canopy temperatures than snow surface (with RMS differences of 1.2 °C and 3.0 °C respectively), and those of sunlit slopes as opposed to slopes facing away from the sun (with RMS differences of 1.6 °C and 3.4 °C respectively), in coincident ASTER imagery. This work demonstrates the use of GOES ABI, and associated challenges, for observing surface temperatures of forested mountain environments with seasonal snow.

Tectonic Geomorphology Of The Jhelum Fault Zone And Its Contiguous Regions In Western Himalaya

The western Himalayan syntaxis represents the region where the major Himalayan structures abruptly curve and the cause of the curvature and the tectonic geomorphology of the region has not been fully explored. The lack of detailed structural maps with extensive field-based data are missing, which is mainly because of the political problems related to border sharing between Pakistan, India, and Afghanistan. However, and fortunately, the usage of satellite derived images has overcome such constrains by providing a robust platform to remotely map such regions. Therefore, the present study was aimed to supplement our previous works in the region by exploring the western portions of the Hazara-Kashmir-Syntaxis. We have used Google terrain imagery to map the evidence for active faulting that involves mapping of triangular facets, displaced and/or faulted topographic ridges, river terraces, alluvial fans and so on. The crosscutting relationships are used to date the faulting events where absolute dates are not available. Our results show that active tectonic deformation is not just limited to the previously mapped structures (e.g. the Kalabagh Fault, the Salt Range Thrust, the Mahesian Anticline, and the Jhelum Fault) but occurs on a broader deformation zone that is delimited by the Chaman fault system in the west, and the Jhelum Fault in the east. The deformation zone in 3D resembles a tectonically formed diamond shaped box that has Salt Range Thrust in front and the Main Boundary Fault at the back with sides delimited by the Chaman and the Jhelum fault systems. The earthquake centroid moment tensor data compliments our geomorphological work, and establishes that transpression is a dominant tectonic process that governs the western regions, which is in comparison to the east where transtension is the norm in the interior Himalayan with reverse and thrust faulting dominant in the frontal regions.

MIP mapping the virtual environment for computer games

The paper describes how MIP-mapping and paging can be used to represent not only terrain imagery, but also terrain elevation. Previously the only things missing to implement Earth coverage were computing power, input/output bandwidth, graphics processing units (GPUs) and techniques to deal with large data sets. The article describes the rendering method that uses the GPU for most of the calculations. Modern graphics accelerators for personal computers allow you to solve problems that require the generation of images of the visual environment of photographic quality in real time. High-quality visualization of large continuous spaces of 3D vegetation is one of the requirements when creating most land transport simulators, as well as many virtual reality applications. Representation of large forest spaces in the form of free-standing tree models that have an acceptable visual quality for close-up display from the observer, it is impossible due to the huge number of primitives required for visualization. The article proposes use parallel calculations in GPU to accelerate rendering. We successfully integrated proposed visualization method into the standard rendering pipeline. For considered tests the application with GPU average ten times faster, than the version using only CPU. The proposed method takes into account the features of the architecture of modern GPUs and allows you to distribute the load on the display between the CPU and GPU. In this case, the method does not require significant resources for visualization. The implementation of the method showed that received speed in most cases is sufficient for the effective application of the method in computer games. The paper also proposes a method for high-quality visualization of large continuous spaces of 3D vegetation.

Association of Secondhand Smoking Exposure With Choroidal Thinning in Children Aged 6 to 8 Years

Secondhand smoking is a risk to adult ocular health, but its effect on children's ocular development is not known. To assess the association between choroidal thickness and secondhand smoking exposure in children. Children aged 6 to 8 years were consecutively recruited from January 2016 to July 2017 from the population-based Hong Kong Children Eye Study at the Chinese University of Hong Kong Eye Centre. All participants underwent detailed ophthalmic investigations. Choroidal thickness was measured by swept-source optical coherence tomography, with built-in software that automatically segmented the choroid layer to analyze its terrain imagery. History of secondhand smoking was obtained from a questionnaire. Multiple linear regression analyses were performed to assess the correlation between choroidal thickness and secondhand exposure when controlling for confounding factors. Analysis began July 2018 and ended in April 2019. The association between children's choroidal thickness and their exposure to secondhand smoking. Of 1400 children, 941 (67.2%) had no exposure to secondhand smoking, and 459 (32.8%) had exposure to secondhand smoking. The mean (SD) age was 7.65 (1.09) years for children in the nonexposure group and 7.54 (1.11) years for children in the exposure group. After adjustment for age, sex, body mass index, axial length, and birth weight, exposure to secondhand smoking was associated with a thinner choroid by 8.3 μm in the central subfield, 7.2 μm in the inner inferior, 6.4 μm in the outer inferior, 6.4 μm in the inner temporal, and 7.3 μm in the outer temporal. Choroidal thinning with also associated with increased number of family smokers and increased quantity of secondhand smoking. An increase of 1 family smoker was associated with choroidal thinning by 7.86 μm in the central subfield, 4.51 μm in the outer superior, 6.23 μm in the inner inferior, 5.59 μm in the outer inferior, 6.06 μm in the inner nasal, and 6.55 μm in the outer nasal. An increase of exposure to 1 secondhand cigarette smoke per day was associated with choroidal thinning by 0.54 μm in the central subfield, 0.42 μm in the inner temporal, and 0.47 μm in the outer temporal. This investigation showed that exposure to secondhand smoking in children was associated with choroidal thinning along with a dose-dependent effect. These results support evidence regarding the potential hazards of secondhand smoking to children.

High-Level Feature Selection With Dictionary Learning for Unsupervised SAR Imagery Terrain Classification

Features are of great importance for synthetic aperture radar (SAR) imagery terrain classification, but low-level features usually readily suffer from the speckle noise and they are incapable or inaccurate to capture some complex and irregular texture structure. In this paper, a novel feature learning framework is proposed to address this problem, in which some mid-level and high-level features are simultaneously learned by exploiting the spatial context constraints and sparse priors. More specifically, the mid-level features served as the intermediates are extracted from several initialized low-level features by the spatial constraints to reduce the influence of the speckle noise. Then, more abstract and discriminative high-level features are learned with an effective dictionary learning algorithm so as to represent the complex structures in SAR imagery. Finally, both artificial synthesis and real SAR imagery are utilized to verify the effectiveness of the proposed framework. It is demonstrated from both quantitative evaluations and visual results that the proposed algorithm performs better than other compared algorithms and the learned high-level feature is robust to the speckle noise and can improve the classification performance.

Distribution of subtidal sedimentary bedforms in a macrotidal setting: The Bay of Fundy, Atlantic Canada

The Bay of Fundy, Canada, a large macrotidal embayment with the World's highest recorded tides, was mapped using multibeam sonar systems. High-resolution imagery of seafloor terrain and backscatter strength, combined with geophysical and sampling data, reveal for the first time the morphology, architecture, and spatial relationships of a spectrum of bedforms: (1) flow-transverse bedforms occur as both discrete large two-dimensional dunes and as three-dimensional dunes in sand sheets; (2) flow-parallel bedforms are numerous straight ridges described by others as horse mussel bioherms; (3) sets of banner banks that flank prominent headlands and major shoals. The suite of bedforms developed during the Holocene, as tidal energy increased due to the bay approaching resonance. We consider the evolution of these bedforms, their migration potential and how they may place limitations on future in-stream tidal power development in the Bay of Fundy.

Examining the Effects of Conformal Terrain Features in Advanced Head‐Up Displays on Flight Performance and Pilot Situation Awareness

AbstractSynthetic vision systems (SVS) render terrain features for pilots through cockpit displays using a GPS database and three‐dimensional graphical models. Enhanced vision systems (EVS) present infrared imagery of terrain using a forward‐looking sensor in the nose of an aircraft. The ultimate goal of SVS and EVS technologies is to support pilots in achieving safety under low‐visibility and night conditions comparable to clear, day conditions. This study assessed pilot performance and situation awareness (SA) effects of SVS and EVS imagery in an advanced head‐up display (HUD) during a simulated landing approach under instrument meteorological conditions. Videos of the landing with various HUD configurations were presented to eight pilots with a superimposed tracking task. The independent variables included four HUD feature configurations (baseline [no terrain imagery], SVS, EVS, and a combination of SVS and EVS), two visibility conditions, and four legs of the flight. Results indicated that SVS increased overall SA but degraded flight path control performance because of visual confusion with other display features. EVS increased flight path control accuracy but decreased system (aircraft) awareness because of visual distractions. The combination of SVS and EVS generated offsetting effects. Display configurations did not affect pilot spatial awareness. Flight performance was not different among phases of the approach, but levels and types of pilot SA did vary from leg to leg. These results are applicable to development of adaptive HUD features to support pilot performance. They support the use of multidimensional measures of SA for insight on pilot information processing with advanced aviation displays. © 2012 Wiley Periodicals, Inc.

Current visual interfaces for acoustical modeling analysis

With the development of advanced noise mapping software, consultants have the ability to present their clients with graphic depictions of sound level distribution in a given area. Most noise mapping software interfaces easily with Auto CAD and Google Earth, where GIS data formats can be imported and exported based on a coordinate system specified by the user. The merging of these technologies can be especially useful where the study site is located in a complex terrain or urban area. This paper describes several case studies where the development of noise maps has been improved from a basic diagram of noise contours lines to a complex, three dimensional imagery of terrain and buildings that can be rendered in Google Earth.

“Picture-in-Picture” Augmentation of UAV Workstation Video Display

Research at the Air Force Research Laboratory has focused on determining the value of combining computer-generated information with live camera video presented on an unmanned air vehicle (UAV) station display. In a previous study, a picture-in-picture (PIP) concept (where video imagery is surrounded by synthetic-generated terrain imagery, increasing the operator's instantaneous field-of-view) was found to reduce landmark search time and enhance operator situation awareness. The present study examined whether PIP display size and symbology overlay registration error impacts performance. Results confirmed that performance on a landmark search task is better when a PIP display was used, particularly with the more compressed video imagery, reducing average designation time by 60%. Also, the registration error between the virtual flags and landmarks was less critical with the PIP capability enabled. This research has potential application to a variety of teleoperated control applications.

P-30: Target Identification on Simulated Terrain Imagery Varying in Resolution

Air-to-ground target identification was found to improve with decreases in background resolution as defined by a satellite-imaging metric. This metric was then compared to a more conventional measure of target and image spatial resolution based on gaussian blur.

Monoplotting applied to high‐resolution satellite imagery

Monoplotting is a well‐known photogrammetric technique for extracting 3D spatial information from single aerial imagery of terrain described by a digital elevation model. The method also offers potential for single‐image analysis of high‐resolution satellite imagery (HRSI). This paper investigates the prospects of single IKONOS and QuickBird images for 3D feature pointcollection and the generation of 3D building models. The implementation of monoplotting functions in the photogrammetric software package ‘Barista’ is described and an experimental determination of the accuracy of monoplotting from IKONOS and QuickBird imagery is reported.

Application of frequency correlation function to radar target detection

Analysis of high-resolution 35 GHz synthetic aperture radar (SAR) imagery of terrain reveals that when point targets, such as vehicles, are viewed at angles close to grazing incidence, they are often difficult to distinguish from tree trunks because the radar cross section (RCS) intensities of the vehicles are comparable to the upper end of the RCS exhibited by tree trunks. To resolve the point target/tree trunk ambiguity problem, a detailed study was conducted to evaluate the use of new detection features based on the complex frequency correlation function (FCF). This paper presents an analytical examination of FCF and its physical meaning, the results of a numerical simulation study conducted to evaluate the performance of a detection algorithm that uses FCF, and the corroboration of theory with experimental observations conducted at 35 and 95 GHz. The FCF-based detection algorithm was found to correctly identify tree trunks as such in over 90% of the cases, while exhibiting a false alarm rate of only 3%.

High resolution 3-D imaging via multi-pass SAR

Spaceborne/airborne synthetic aperture radar (SAR) systems provide high resolution two-dimensional terrain imagery. The paper proposes a technique for combining multiple SAR images, acquired on flight paths slightly separated in the elevation direction, to generate high resolution three-dimensional imagery. The technique could be viewed as an extension to interferometric SAR (InSAR) in that it generates topographic imagery with an additional dimension of resolution. The 3-D multi-pass SAR imaging system is typically characterised by a relatively short ambiguity length in the elevation direction. To minimise the associated ambiguities we exploit the relative phase information within the set of images to track the terrain landscape. The SAR images are then coherently combined, via a nonuniform DFT, over a narrow (in elevation) volume centred on the 'dominant' terrain ground plane. The paper includes a detailed description of the technique, background theory, including achievable resolution, and the results of an experimental study.

Stochastic model-based processing for detection of small targets in non-Gaussian natural imagery

Stochastic background models incorporating spatial correlations can be used to enhance the detection of targets in natural terrain imagery, but are generally difficult to apply when the statistics are non-Gaussian. Chapple and Bertilone (see Opt. Commun., vol.150, p.71-76, 1998) proposed a simple stochastic model for images of natural backgrounds based on the pointwise nonlinear transformation of Gaussian random fields, and demonstrated its effectiveness and computational efficiency in modeling the textures found in natural terrain imagery acquired from airborne IR sensors. In this paper, we show how this model can be used to design algorithms that detect small targets (up to several pixels in size) in natural imagery by identifying anomalous regions of the image where the statistics differ significantly from the rest of the background. All of the model-based algorithms described here involve nonlinear spatial processing prior to the final decision threshold. Monte Carlo testing reveals that the model-based algorithms generally perform better than both the adaptive threshold filter and the generalized matched filter for detecting low-contrast targets, despite the fact that they do not require the target statistics needed for constructing the matched filter.

Geometric reasoning under uncertainty for map-basedlocalization

Map-based navigation in outdoor terrain lacking man-made structures or other highly distinctive landmarks can produce severe localization problems. This paper presents an approach to navigation which implements high level geometric reasoning and matching strategies based on those used by skilled human navigators. This approach, which is demonstrated on a real example involving imagery of mountainous terrain obtained with a video camera and USGS map data, is designed to avoid many of the pitfalls occurring when an attempt is made to navigate by modeling the environment mathematically. It exploits feature attributes which cannot be easily expressed quantitatively but are central to the successful human navigation process.

Glacier snow line mapping using ERS-1 SAR imagery

This article paper evaluates the effectiveness of ERS-1 synthetic aperture radar (SAR) imagery for mapping movement of the transient snow line in a temperate glacier basin during an ablation season. The two primary objectives of this study are to normalize the topographically induced distortions (radiometric and geometric) inherent in SAR imagery of rugged terrain and to delineate the snow line in the normalized imagery. The radiometric distortions are normalized with a cosine correction, and the image texture is enhanced to take advantage of the spatial distribution of tonal variations within each image. To minimize geometric distortions and georeference the imagery, each cosine corrected/texture enhanced SAR image is orthorectified to an error of approximately 60 m using a DEM and satellite orbital and ephemeris data. A supervised classification is performed on the orthorectified imagery to map the spatial distribution of snow and glacial ice within the basin. The visual boundary between the wet snow and glacier ice surfaces on the orthorectified images is within 75 m horizontally of the snow line obtained from field data. The glacier boundary is also discernible to within 75 m of the surveyed glacier outline. Several isolated bare ice areas on the lower glacier give a low return, similar to wet snow, resulting in some confusion between glacier ice and wet snow. It is speculated that the incident wave is lost within the crevasses and surface runoff runnels due to specular reflection within the features. Despite the localised confusion between glacier ice and wet snow, the wet-snow line and can be mapped reasonably well and in a timely manner using ERS-I SAR imagery.

Fractal Modeling of Natural Terrain: Analysis and Surface Reconstruction with Range Data

In this paper we address two issues in modeling natural terrain using fractal geometry: estimation of fractal dimension, and fractal surface reconstruction. For estimation of fractal dimension, we extend the fractal Brownian function approach to accommodate irregularly sampled data, and we develop methods for segmenting sets of points exhibiting self-similarity over only certain scales. For fractal surface reconstruction, we extend Szeliski's regularization with fractal priors method to use a temperature parameter that depends on fractal dimension. We demonstrate both estimation and reconstruction with noisy range imagery of natural terrain.

Zooming of terrain imagery using fractal-based interpolation

Terrain imagery is routinely created from digital terrain elevation and feature data for use in a variety of applications ranging from civilian construction projects to military mission planning. The underlying terrain is often used as a background for displaying the features. However, the features are usually known at higher resolution than the terrain. Conventional methods for enlarging a terrain image (replication, interpolation) can lead to blurred and blocky backgrounds, which are distracting and make examination of the features difficult. This paper presents a fractal-based interpolation method that adds realistic synthetic texture to the enlarged terrain images. Several examples of terrain images enlarged using this process are shown.

The correlation between geochemical data and SPOT satellite imagery of lateritic terrain in southern Mali

Abstract Detailed geochemical mapping of superficial lateritic formations is compared with recent high-resolution SPOT satellite images in the Dagadamou prospect in southern Mali. The two main landscape features standing out in SPOT images are expressed by thematic indices derived from multispectral data. They reflect the distribution of vegetation cover and the distinction between silty clay soils in the valleys and ferruginous duricrust exposed on the plateaus. Geochemical differentiation factors are closely related to the nature of sampled materials and reflect the relative amounts of major constituent minerals estimated by normative calculation. Duricrust samples with high Fe and Al content are also enriched in trace elements, P, V, Cr, As, Mo, Nb and Cu, immobilized in the weathering profile with secondary oxihydroxide minerals. Soils of flats are composed mainly of quartz and kaolinite; they also concentrate heavy minerals characterized by high contents of Zr, Ti, Ce and Y. Accumulation of detrital material at the periphery of duricrust plateaus is marked by a geochemical halo of higher contents in Zr and quartz at their periphery. This feature is clearly visible on SPOT imagery as a zone of high reflectance, devoid of vegetation. The density of vegetation on duricrust is related to its kaolinite content. Its distribution is characterized by a striped pattern, which is probably controlled by bedrock lithological structures preserved in the lateritic cover. This study shows the relationships, both direct and indirect, existing between spectral reflectance and geochemical composition of superficial lateritic formations. Many other landscape features identified with high resolution on SPOT images provide complementary information, which could be very helpful at various stages of geological and mineral exploration in lateritic terrain.

Octree data structures and perspective imagery

The fundamental elements of perspective image generation from octree encoded graphics databases are examined. Procedures are presented for the encoding of spatially enumerated objects into an octree which is stored as a doubly-linked list. A perspective image rendering procedure is developed, based on raycasting, and involves a bidirectional traversal of the octree together with an adaptive level-of-detail control mechanism. The concepts and algorithms are verified by the synthesis of perspective terrain imagery.