Conventional Aerial Photography Research Articles

Mapping of mudflats with UAV images in La Bocana de Iscuandé, Colombian Pacific coast

Conservation planning for marine-coastal environments requires updated and detailed maps; the aim of this work is to generate detailed maps for two mudflats in the Iscuandé River Delta (Bocana de Iscuandé) in the Colombian Pacific Coast (Department of Nariño). These are important areas for fauna, especially migratory shorebirds. To address this problem, this study investigated the use of unmanned aerial vehicles (UAVs) as an alternative for collecting detailed mapping information in areas of difficult access using photogrammetric methodsand a geographic information system (GIS). UAV images were used to generate maps with a high level of detail at a scale of 1:10,000 that include detailed information about environments such as mudflats and mangroves which had not been mapped before. UAVs are a practical tool for mapping places where weather and access conditions hinder the use of satellite images or conventional aerial photography. They are also useful for mapping areas with high temporal and spatial variability, such as mudflats, where other platforms may not reveal their short-term dynamics. Our results show that this technique has a high potential for mapping such environments, and reveal that the Iscuandé mudflats aremaintained by a relative equilibrium between the ebb and flow of waves and tides, and are also influenced by the local climate. This type of application provides critical data for conservation and management strategies of areas with great ecological importance.

APPLICATION OF REMOTE SENSINGTECHNIQUES IN PETROLEUM EXPLORATION : THE INDONESIAN EXPERIENCE

Since the seventies, remote sensing data have been widely used in petroleum exploration in Indonesia. These include Landsat. Spot and Radar imageries, apart from the conventional aerial photographs. Examples from Nias Island, East Kalimantan Basin and Irian Jaya, will be presented to show the extensive application of remote sensing techniques in general geological mapping and hydrocarbon exploration.

ORIENTATION OF UAV IMAGE BLOCKS BY SURFACE MATCHING

Abstract. Topographic maps are produced in Portugal by the Army Geospatial Data Centre, based on a geographical database collected from aerial photography in resolutions from 0.30 to 0.50 m. Each map sheet is revised with an update interval of 10 years or more. Many changes, such as new roads or power lines, would be possible to update with much higher frequency using UAV imagery. Although the nominal scale of the published paper map sheets is 1 : 25,000, the actual positional accuracy requirement is of 1 meter, which is compatible with larger scales. Exterior orientation parameters obtained by UAV navigation equipment does not have enough accuracy for that. This paper deals with a method to automatically improve the UAV exterior orientation, intended to be compatible with the positional accuracy standards of the geographic database. The method is based on matching a point cloud derived from UAV imagery, without GCPs, with a reference DSM obtained from conventional aerial photographs, which were oriented by standard aerial triangulation. Results allowed to improve the UAV data to a positional accuracy of 1 meter, making it compatible with the requirements established for the geographic database.

Panta Rhei

In this paper we present a reconstruction of the kinematics of the Tschadinhorn rock glacier using multi-temporal conventional (metric) aerial photographs (1954–2015) and additional non-metric aerial photographs (2016, 2017) taken with in-house unmanned aerial vehicles (UAVs). A rotary-wing aircraft (hexacopter twinHEX v.3.0) was used in 2016 and a fixed-wing aircraft (QuestUAV) in 2017. The historical image data was acquired from the Austrian Federal Office of Metrology and Surveying (BEV). Both a digital orthophoto (DOP) and a digital terrain model (DTM) were computed for each given epoch. Precise georeferencing of the image data was carried out in the Austrian Gauss-Krüger M31 coordinate system using available aerotriangulations (ATs) of BEV and additional ground control points (GCPs) measured geodetically during both UAV campaigns. Change detection analysis provided multi-temporal 2D flow velocity fields. Subsequently, these data were collated to produce a simpler velocity graph showing clearly the temporal evolution of the flow velocity of Tschadinhorn rock glacier: A maximum mean annual flow velocity of 3.28 m/year was obtained for 2014–2015, while the lowest annual flow velocity of 0.16 m/year was observed for 1969–1974. The velocity graph also revealed that 1954–2009 was characterized by generally moderate activity (0.16 – 0.79 m/year) and that much higher flow velocities have prevailed since 2009. The present value for 2016–2017 is 1.92 m/year.

Spatial Changes and Land Use of Arable Land in China

Numerous concerns have been raised in China over the issues of limited arable land resources and food security in China. Especially, the record levels of soil pollution and the conversion of the arable land become the serious threat to the nation’s capacity to produce adequate levels of staple cereal crops for Chinese people. Most of arable land, only 15% of the country, mainly concentrated on the central eastern coast and along the Yangtze and Yellow river valleys which had the highest sediment deposit among the lands in China. An agricultural land in China was classified into four categories including arable land. The survey of spatial distribution and types of land use by in China established by remote sensing data and conventional aerial photography showed main land use features and the spatial pattern and processes of land use change for 15 regions covering China. The agricultural land area in 2015 was increased by 64.9% from that in 1960 while the changes of the arable land area ranged from decrease of 6.6% in 1980 to increase of 20.2% in 1990. Conclusively, we assume that Chinese government may have to figure out the practically adequate arable land area to produce safe food for people in China, bearing in mind of 135 million ha that is a minimum threshold to ensure adequate food production. The spatial change in arable land area in China.

Best Practices in Low Altitude UAV Mapping for GIS Applications

Aerial data collection for use in GIS has, in the past, been an expensive undertaking and required significant capital expenditures for metric aerial cameras, aircraft purchase, maintenance, fuel, insurance, and not to mention a significant cost for specialized labour. The advent of Unmanned Aerial Vehicles (UAV’s), and their increasing mainstream use, has created an alternative to conventional aerial photography for the creation of Digital Surface Models (DSMs) and orthophotos. The standards of traditional aerial data collection have been spelt out in long-established guidelines by the American Society of Photogrammetry and Remote Sensing. UAV operators, often non-specialist newcomers to the field, have side-stepped these standards and have no means to ensure the quality and reproducibility of their data. I propose a set of simple best-practices that can be adopted both by UAV operators and their clients to establish some measure of Quality Assurance and Quality Control while maintaining the cost-advantage afforded by UAVs. These practices can be grouped into five main areas: 1) proper camera and lens selection, 2) pre-calibration of cameras used for photogrammetric mapping, 3) establishing accurate ground-control across the area of mapping and not relying on consumer-grade GNSS for air stations, 4) pre-flight calculation of flight parameters based on a clear accuracy requirement, 5) flying at a sufficient height to minimize relief displacement so as to create artifact-free orthophotos. It is hoped that a better understanding of the underlying principles of photogrammetry by both UAV operators and their clients will guarantee the proper implementation of UAVs for high-accuracy GIS data collection in the future.

ERROR ANALYSIS FOR THE AIRBORNE DIRECT GEOREFERINCING TECHNIQUE

Abstract. Direct Georeferencing was shown to be an important alternative to standard indirect image orientation using classical or GPS-supported aerial triangulation. Since direct Georeferencing without ground control relies on an extrapolation process only, particular focus has to be laid on the overall system calibration procedure. The accuracy performance of integrated GPS/inertial systems for direct Georeferencing in airborne photogrammetric environments has been tested extensively in the last years. In this approach, the limiting factor is a correct overall system calibration including the GPS/inertial component as well as the imaging sensor itself. Therefore remaining errors in the system calibration will significantly decrease the quality of object point determination. This research paper presents an error analysis for the airborne direct Georeferencing technique, where integrated GPS/IMU positioning and navigation systems are used, in conjunction with aerial cameras for airborne mapping compared with GPS/INS supported AT through the implementation of certain amount of error on the EOP and Boresight parameters and study the effect of these errors on the final ground coordinates. The data set is a block of images consists of 32 images distributed over six flight lines, the interior orientation parameters, IOP, are known through careful camera calibration procedure, also 37 ground control points are known through terrestrial surveying procedure. The exact location of camera station at time of exposure, exterior orientation parameters, EOP, is known through GPS/INS integration process. The preliminary results show that firstly, the DG and GPS-supported AT have similar accuracy and comparing with the conventional aerial photography method, the two technologies reduces the dependence on ground control (used only for quality control purposes). Secondly, In the DG Correcting overall system calibration including the GPS/inertial component as well as the imaging sensor itself is the limiting factor to achieve good object space.

Point clouds from oblique stereo-imagery: Two outcrop case studies across scales and accessibility

Digital elevation models (DEM) were generated from oblique stereo-images acquired with a handheld digital camera. Two model scenarios are considered. Firstly, at local outcrop scale, with easy access, and distances between camera and outcrop varying between c. 40 m and c. 120 m, a very dense and high resolution point cloud was produced. The quality of the point cloud was evaluated against a terrestrial laser scan derived model of the same outcrop. The deviation between the two datasets varies between 0.02 m and 0.09. This is negligible for most geological purposes and illustrates the potential of using terrestrial photogrammetry at local outcrop scale as an alternative to lidar generated elevation data. Secondly, the method is explored at a regional scale, where a set of oblique stereo-images of a remotely located steep inaccessible mountain cliff was collected from a helicopter at a distance of c. 2–5 km under challenging and unfavourable conditions. The quality of the point cloud was evaluated against two elevation models extracted from conventional aerial photographs. Compared to a DEM extracted from monochrome aerial photographs, such as are often the only available topographic source for remote regions, a clear improvement in resolution is observed. Comparison with a DEM extracted from high resolution coloured aerial photographs shows the two digital elevation models to be very similar in resolution and with root mean square deviation (RMSE of 6.0 m).

Piping as a process of gully erosion in small-format aerial pothography : A short note

No abstract available.

THE CAUSES AND CONSEQUENCES OF ENVIRONMENTAL CHANGES IN GEDAREF, SUDAN

ABSTRACTStudies in several countries in Africa using remote sensing and conventional aerial photography indicate acute land degradation, which is an issue of global concern as it poses a great threat to stability of world climate, biodiversity and geodiversity. Mechanized scheme farms schemes in Sudan are perceived as a major cause of environmental degradation and land losses. Investigations were thus conducted within forests reserves and natural forests sites in the Gedaref area in eastern Sudan where mechanized farmers and traditional land users inside and outside forests reserves represented the target categories for the study. The target groups were interviewed to evaluate their knowledge, attitudes and perceptions with respect to the causes of environmental degradation of soil, forests, agricultural productivity and animal resources. Interviews were conducted among 162 farmers in addition to group discussion among key informants. The results are presented as descriptive statistics, which indicate that forest conversion to agriculture associated with over‐cutting has been the main factor contributing to land degradation in Gedaref State. The results also indicate that there are other causes that include sectoral policies that contradict each other, affecting land ownership. The present study demonstrates the need for integrated policies to facilitate sustainable use and management based on local community's partnership and to encourage communal property rights and local‐level institutional regimes that ensure sustainable resource management and protection of biodiversity and geodiversity across Sudan. Copyright © 2012 John Wiley & Sons, Ltd.

Assessing the utility of lidar remote sensing technology to identify mule deer winter habitat

Winter habitat for mule deer (Odocoileus hemionus) is a critical concern throughout interior British Columbia, Canada. In winter, mule deer require a food source of twigs and woody browse and face significant winter snow cover. A range of studies have established that good winter range for mule deer reduces the impact of a negative energy balance by providing adequate food, good vegetative cover, and shallow snow. Generally, sites with old Douglas-fir and moderate to high canopy cover on warmer aspects and moderately steep slopes are preferred, resulting in a suite of structural stand conditions, which can be used to map mule deer winter range habitat within the interior Douglas-fir range. The increased availability of light detection and ranging (lidar) data to management agencies and the recent adoption of lidar technology by forestry agencies allow us to assess the capacity of this technology to map some variables important to winter mule deer habitat suitability, using criteria similar to those defined using conventional aerial photography. Results indicate that lidar-derived solar radiation regime, elevation, and overstorey cover are all useful attributes in decision-tree models relating lidar to conventionally derived descriptors of mule deer winter habitat. These lidar-derived models describe up to 75% of the variance in overall stand structure and confirm that this technology is a viable tool which can be used to assess habitat throughout this region.

Accuracy assessment of aerial photographs acquired using lighter‐than‐air blimps: low‐cost tools for mapping river corridors

AbstractMonitoring river systems with repeat aerial photography is a powerful tool although the temporal resolution of surveys is rarely performed at anything better than annual time‐scales. In recent years, a variety of low‐cost aerial platforms for acquiring aerial photography have emerged. While these economical options may facilitate more frequent repeat surveys, the accuracy of imagery needs further consideration.The accuracy of imagery obtained from a Lighter‐Than‐Air Blimp is investigated through two simple experiments. The first looks at the geospatial error of aerial photographs derived using five geometric transformation models, and the sensitivity of the photo registration quality to various ground control point (GCP) configurations and densities. At high GCP densities, higher order polynomial transformation models provide the highest quality registrations. However, at more modest GCP densities (i.e. 19–28 GCPs Ha−1), simple aerotriangulation and 2nd order polynomial transformation models perform modestly, resulting in registration errors at standards equal to or better than obtained with conventional aerial photography (e.g. 0.5–1 m). The quality of image registration is highly dependent on the configuration of GCPs. In a second experiment, the practical utility of producing a mosaic of blimp acquired imagery is explored over a kilometre long braided reach. Even at relatively low GCPs densities (e.g. 9 GCPs Ha−1), a mosaiced aerial of the entire reach can be produced of adequate quality to support bar‐scale mapping of patch‐scale features. The survey required less than a single day of field work and laboratory processing, and presents a cost‐effective alternative to traditionally commissioned flights. Copyright © 2008 John Wiley & Sons, Ltd.

Using multitemporal digital elevation model data for detecting canopy gaps in tropical forests due to cyclone damage: An initial assessment

Abstract The detection and mapping of canopy disturbance caused by natural events such as cyclones in tropical rainforests is important for monitoring and understanding rainforest dynamics and recovery. In February 1999 tropical cyclone Rona crossed the coastline of Far North Queensland, Australia, causing significant damage to the rainforest canopy in some areas. This paper examines the application of multitemporal canopy digital elevation models (DEMs) generated by a NASA‐operated airborne radar mapping system called TOPSAR in 1996 and 2000, for detection of canopy disturbance caused by cyclone damage. Canopy damage was mapped here by identifying areas with a significant decrease in canopy height estimated from the difference of the 1996 and 2000 TOPSAR DEMs. Conventional aerial photographs, flown shortly after the cyclone (March 1999), were used to validate the resulting map of cyclone damaged rainforest canopy. The results showed that the DEM‐derived canopy damage map performed reasonably well when comparing the spatial distribution and size of damaged areas, while taking into account the time difference between cyclone damage and the second radar acquisition. Some errors were encountered on the steeper slopes which were related to terrain distortions inherent in radar images of steep terrain. The height accuracy of the DEM was close to the depth of some of the gaps being mapped, which also contributed to errors. Even so, the results demonstrate there may be potential for weather‐independent, regional‐scale mapping of forest canopy change from imaging radar that is not always possible from traditional optical means of measuring canopy elevation, for example, airborne laser data and stereo aerial photography. This may be possible in relatively flat areas, provided the second radar acquisition occurs within months of the damaging event. Further algorithm refinement is required to improve its robustness and the range of topographies where this approach can provide reliable estimates of the extent of canopy disturbance.

A review of trends within archaeological remote sensing in alluvial environments

Archaeological remote sensing encompasses a broad range of techniques from conventional aerial photography, passive and active airborne and satellite remote sensing to ground-based geophysical surveys. The aim of this paper is to review the present trends in the application of remote sensing within alluvial geoarchaeology. A number of broad themes emerge reflecting a hierarchy based on the view of alluvial environments within the earth sciences, ranging from catchment-wide analysis through to study of geomophologically homogeneous river reaches and individual sites, sometimes associated with clearly defined geomorphological events. This framework places cultural activity firmly within its containing and constraining natural landscapes. Beyond scale, the influence of emerging technologies may be seen in the development of new remote sensing techniques, powerful computer hardwares and softwares and the steady technology-driven move from reporting by two-dimensional static maps to three-dimensional interactive and immersive visualization. Copyright © 2006 John Wiley & Sons, Ltd.

Mapping small areas using a low‐cost close range photogrammetric software package with aerial photography

AbstractGenerating maps of small areas using conventional aerial photography is of great interest for small engineering firms. The main problem is the high cost of the sophisticated digital photogrammetric workstations usually employed. In this paper, a low‐cost close range photogrammetric software package is used to measure the three‐dimensional coordinates of points on the land surface from a photogrammetric flight at a scale of approximately 1:5000. Furthermore, the influence of the type of scanner used to digitise photographs (consumer‐grade or photogrammetric scanner), the resolution of the digital images and the number of control points required are examined. The root mean square errors obtained at the check points, using a low‐cost close range software package, scanning aerial images with a photogrammetric scanner and 24 ground control points, were around 116 mm for X and Y coordinates, and 191 mm for Z. These levels of accuracy allow the generation of planimetric maps at a scale of 1:1500 and topographic maps with a contour interval of around 1 m. When the images were scanned with a consumer‐grade scanner, the root mean square errors were around 150 mm for X and Y, and 271 mm for Z.

Airborne remote sensing for landslide hazard assessment: a case study on the Jurassic escarpment slopes of Worcestershire, UK

This paper describes the application of airborne remote sensing to the study of landslides on the clay-dominated slopes of the Cotswolds Hills between the towns of Broadway, Worcestershire, and Snowshill, Gloucestershire, in the UK. The project involved an initial desk study, airphoto interpretation and field survey in order to provide detailed information about the nature and extent of the landsliding in the area. High-resolution Airborne Thematic Mapper (ATM) imagery was acquired by the NERC Airborne Remote Sensing Facility, which was subsequently processed in order to develop a remote sensing method for landslide identification using airborne multispectral data. A range of image processing methods are described including colour composite enhancement and thermal imaging, while the focus of the paper will be on the development of a semi-automated method of landslide identification using image classification and texture analysis. Results from the first stage of the study have shown that the use of image processing techniques such as colour composites and thermal imaging can provide information on the ground surface not visible in conventional aerial photography. In this case study, this has included more detailed geomorphological information on landsides in the area and the nature of the cambering and gulls at the top of the escarpment. The second part of the study has investigated the use of image texture enhancement as a method of landslide identification, applied in isolation and incorporated into an image classification scheme as a semi-automated method of landslide identification. Results from this investigation indicate that landslides can be identified automatically with a high degree of accuracy (83%) and that by using image texture, the image classification technique is able to successfully differentiate between areas of landslide activity and stable slopes in the airborne imagery. Its is clear from the results of this study that in order to identify landslides in these types of clay-dominated terrains, image texture must be used. Inland landslides, like those on the Cotswolds escarpment, do not have a spectral signature but they do exhibit a distinct spatial signature that allows them to be identified in airborne imagery using textural analysis. The semi-automated method of landslide identification described in this paper represents a rapid method of terrain evaluation and landslide hazard assessment, which can be undertaken prior to more detailed field mapping.

Predicting Cotton Lint Yield Maps from Aerial Photographs

It is generally accepted that aerial images of growing crops provide spatial and temporal information about crop growth conditions and may even be indicative of crop yield. The focus of this study was to develop a straightforward technique for creating predictive cotton yield maps from aerial images. A total of ten fields in southern Georgia, USA, were studied during three growing seasons. Conventional (true color) aerial photographs of the fields were acquired during the growing season in two to four week intervals. The aerial photos were then digitized and analyzed using an unsupervised classification function of image analysis software. During harvest, conventional yield maps were created for each of the fields using a cotton picker mounted yield monitor. Classified images and yield maps were compared quantitatively and qualitatively. A pixel by pixel comparison of the classified images and yield maps showed that spatial agreement between the two gradually increased in the weeks after planting, maintained spatial agreement of between 40% and 60% during weeks eight to fourteen, and then gradually declined again. The highest spatial agreement between a classified image and a yield map was 78%. The highest average agreement was 52% and occurred 9.9 weeks after planting. The visual similarity between the classified images and the yield maps were striking. In all cases, the dates with the best visual agreement occurred between eight and ten weeks after planting, and generally, during July for southern Georgia. This method offers great potential for offering cotton farmers early-season maps that predict the spatial distribution of yield. Although these maps can not provide magnitudes, they clearly show the resulting yield patterns. With inherent knowledge of past performance, farmers can use this information to allocate resources, address crop growth problems, and, perhaps, improve the profitability of their farm operation. These maps are well suited to be offered to farmers as a service by a crop consultant or a cooperative.

Synergistic Fusion of GPS and Photogrammetrically Generated Elevation Models

Digital elevation models (DEMs) produced from photogrammetric data sources have long relied on the use of ground control points to give them scale and orientation. However, in areas such as coastlines, landslides, or glaciers, where identification of suitable natural features and pre-marking is difficult, the use of conventional ground control may be unfeasible. This paper reports on research that uses independently collected DEMs derived from kinematic GPS to orient surfaces produced by aerial photogrammetric methods, using a least-squares surface matching algorithm. During algorithm development, three stages of testing were carried out, using increasingly more complex datasets. Initially, simulated surfaces were used to validate the matching theory and program. Then, a DEM derived from conventional aerial photography was matched with a GPS model, highlighting the effectiveness of surface matching to recover systematic errors in datasets. Finally, surfaces derived from small format digital imagery were successfully fused with wireframe GPS surfaces, the high redundancy and automation potential creating an elegant and cheaper alternative to photocontrol.

Reducing the cost of multi-spectral remote sensing: combining near-infrared video imagery with colour aerial photography

Land managers are often confronted with management problems that could be addressed using decision support or management information systems. The use of such tools, however, depends on the availability of appropriately resolved spatial data. One source of such data is multi-spectral remotely sensed imagery. The cost of such imagery, particularly where environmental goals are most important, is often prohibitive. Even when the cost of such imagery can be met, other factors, such as cloud cover for satellite-based systems or sensor scheduling for sophisticated airborne systems, may mean that imagery is not available. This paper investigates the utility of a system that combines near-infrared imagery from a video camera with conventional medium-format aerial photography deployed in a light aircraft platform. Previously, imagery obtained from video cameras has suffered from limited spectral range and from significant image motion effects. These problems were eliminated by the use of an electronic-shutter charge-coupled device video camera with a strong IR response. The systems components and the approach to their operational deployment are described and the options for transforming the raw imagery into survey coverage discussed. The image quality and cost is presented for a site characterisation application where the aim is the generation of normalised difference vegetation index values. It is concluded that the system has significant potential utility for decision support and land-management applications.

Monitoring of gully erosion in the Central Ebro Basin by large-scale aerial photography taken from a remotely controlled blimp

Large deep gullies (Span. barrancos) are some of the most important sediment sources in the semi-arid environment of the Central Ebro Basin. They are incised into the Quaternary valley bottoms (Span. vales), which are characteristic landforms in this area. In the research project EPRODESERT ( E valuation of Pro cesses Leading to Land Degradation and Desert ification under Extensified Farming Systems), the development of a large barranco system is being investigated by different methods, including documentation and monitoring by aerial photography. Geomorphological forms and processes, such as sheet wash, rill and gully erosion, cannot be documented sufficiently by conventional remote sensing methods. Spatial and temporal resolution of satellite sensors as well as of conventional aerial photography do not correspond to the scale and dynamics of geomorphological processes. With a specially designed hot-air blimp as a sensor platform, large-scale aerial photographs were obtained from the Barranco de las Lenas specifically aimed at the scientific demands (very high spatial and temporal resolution). The development of the gully is documented and its dynamics are evaluated by a sequence of six aerial photographs taken between 1995 and 1998.