Oblique Aerial Photographs Research Articles

River bed changing in the lower Potenza Valley (mid-Adriatic Italy). A geo-archaeological approach to historical documents

This paper presents the results of an integrated survey project aiming to achieve the diachronic reconstruction of changes in river beds during historical times in the Potenza Valley, in mid-Adriatic Italy. Here intensive surveys arc being carried out by a team from Ghent University (dir. F.VERMEULEN), especially in and around the Roman colony of Potentia, at the mouth of the river. They are aimed at studying occupation history and the relationship man-landscape in this valley between the Apennines and the Adriatic Sea. Interdisciplinary approaches include low altitude aerial photography, systematic archaeological field walking, artefact studies, re-study of excavated evidence, detailed geomorphologic field mapping, geophysical surveys and fine topographic mapping. Thanks especially to active oblique and vertical aerial photography, geomorphologic fieldwork and corings it is now possible to reconstruct a complete frame of the important changes that have affected the river bed during the last two millennia. The archaeological evidence concurs explicitly with the environmental data to understand and determine the general timing of this evolution, allowing us to measure the interaction between mankind and environment through time. Newly found archive documents can now contribute to shed light on the exact chronology of the river bed shifts, giving details on the events of the last centuries, when human interference was much more consistent. These documents belong to the wide family of pre-geodetic maps (such as the so called cabrei) and the first cadastres (19(th) century). The georeferenciation of these cadastre maps (including those from the well-known 19(th) century Catasto Gregoriano) in the GIS of the Potenza Valley Survey-project offers now the possibility to date several palaeo-channels detected among the aerial imagery and with the help of intensive and integrated geomorphologic survey.

MINNESOTA NORTH SHORE AND DULUTH-SUPERIOR HARBOR SPILL RESPONSE STRATEGIES

ABSTRACT The Minnesota Lake Superior shoreline (Minnesota'S “North Shore”) is characterized by a rocky shoreline with stretches of sand, gravel and cobble as well as several stream and ditch inlets into Lake Superior. The risk of spills is from both land and water. The 150 plus mile stretch of shoreline has a very limited amount of response equipment or nearby responders. The Duluth-Superior Harbor is at the estuarine mouth of the St. Louis River and is divided by the Minnesota and Wisconsin border. The harbor includes sensitive shorelines and habitats, numerous stream, ditch and storm sewer outfalls, as well as an active shipping industry. Geographic Information System (GIS) is a great tool for conducting data analysis and planning. GIS allows users to analyze and visualize large volumes of data to make decisions quickly. While many spill response planners use GIS as a planning response tool, many responders do not have the training and equipment to make efficient use of the capabilities of GIS. This project uses GIS to gather and analyze available data and then put it into a useful “hardcopy” visual format for responders to use in the field. Maps produced from various GIS data sources outline the response strategies for sensitive areas to be protected; types and quantities of response equipment needed; access areas; and other important features. These “hardcopy” displays can be included in contingency plans. Larger laminated versions can be stored with response equipment caches. For response planners that are more familiar with GIS, the tool includes several useful features including “clickable” hyperlinks that connect to georeferenced oblique aerial photos of the Lake Superior shoreline. Also included are GIS data from U.S. EPA and NOAA, including sensitive environment, economic and cultural resources; potential spill sources; and response resources. Where available, sewer data for both sanitary and storm sewers is included, along with high resolution aerial photos; navigation charts; highway stream crossing data; and other habitat information. These various data sources are valuable tools for spill response planners to more accurately and effectively develop workable response strategies and also for use during an actual response to more effectively and efficiently direct responders and resources. This GIS product also incorporates an Access database which allows for easy report generation and information updating.

Hyperspectral imagery for mapping intertidal vegetation at Roberts Bank tidal flats, British Columbia, Canada

This study assesses the effectiveness of hyperspectral airborne imagery to map the intertidal vegetation at Roberts Bank, a large salt marsh and tidal flat complex in the Fraser River delta, British Columbia, Canada. This ecosystem is an important habitat for migratory and resident birds and fish and is part of the largest single salmon-producing stream in the world, the Fraser River. Imagery acquired by the compact airborne spectrographic imager (CASI) was radiometrically and geometrically corrected and mosaicked. A simple maximum likelihood classifier was used to classify intertidal vegetation cover. Training and test sites were collected using field observations and oblique aerial photographs. Seven vegetation-substrate classes were accurately (92.3%) classified, ranging from muddy sediments in the regularly inundated tidal flat and low marsh areas, to higher marsh communities of cattails, grasses, sedges, and rushes. This study showed that both the hyperspectral and hyperspatial characteristics of the CASI imagery were important for achieving high separability among the classes due to reduced spectral mixing of different substrates at the subpixel scale when compared with simulated Landsat and Ikonos imagery.

The evidence for shrub expansion in Northern Alaska and the Pan‐Arctic

AbstractOne expected response to climate warming in the Arctic is an increase in the abundance and extent of shrubs in tundra areas. Repeat photography shows that there has been an increase in shrub cover over the past 50 years in northern Alaska. Using 202 pairs of old and new oblique aerial photographs, we have found that across this region spanning 620 km east to west and 350 km north to south, alder, willow, and dwarf birch have been increasing, with the change most easily detected on hill slopes and valley bottoms. Plot and remote sensing studies from the same region using the normalized difference vegetation index are consistent with the photographic results and indicate that the smaller shrubs between valleys are also increasing. In Canada, Scandinavia, and parts of Russia, there is both plot and remote sensing evidence for shrub expansion. Combined with the Alaskan results, the evidence suggests that a pan‐Arctic vegetation transition is underway. If continued, this transition will alter the fundamental architecture and function of this ecosystem with important ramifications for the climate, the biota, and humans.

Student Aerial Photography

Professional aerial photography missions are generally outside the reach of most students and faculty involved with teaching and research. Oblique aerial photography using handheld cameras for image acquisition from a light high‐wing aircraft offers an excellent learning experience for students in a first course in remote sensing and offers a useful research tool for graduate students and faculty engaged in environmental investigations. This paper is essentially a guide, covering all aspects of hand‐held camera aerial imaging and the subsequent processing needed to produce low‐obliques, stereograms, anaglyphs, and flight line mosaics. Scales, ground coverage distances, and stereogram and mosaic timing intervals, are included along with a section on the calculations used to produce these numbers. A list of additional resources concludes the paper.

Satellite image based vegetation classification of a large area using limited ground reference data: a case study in the Usa Basin, north-east European Russia

Predicted global changes can be studied effectively by combining spatially explicit data sets on vegetation and other landscape properties with process models. However, detailed knowledge of the vegetation distribution of remote Arctic areas is relatively scarce. This paper shows how a mesoscale vegetation and land cover classification of a large, remote Arctic area can be conducted at a fine spatial resolution (30 m cell size) using a limited ground reference data set. The study area is the catchment of the River Usa (93 500 km2) in north-eastern European Russia. Vegetation zones in the Usa Basin range from taiga in the south to forest-tundra and tundra in the north, and to alpine in the Ural mountains in the east. Classification was done using a mosaic of spectrally adjusted Landsat TM5 images from five different dates and a semi-supervised method. Ground reference data were collected during the summers of 1998, 1999 and 2000. Accuracy of the 21-class vegetation type/land cover classification produced was tested against test points interpreted from oblique aerial photographs taken from a helicopter (logistic limitations prohibited the collection of representative ground reference data). The main vegetation types (forests, willow dominated stands and meadows, peatlands, tundra heaths, mainly unvegetated areas, and water bodies) were distinguished with relatively high accuracy: 84% of the test points were classified correctly. Spatially detailed land cover data sets like the one described here allow detailed landscape-level analysis and process modelling on many different subjects.

The first two years of an inlet: sedimentary dynamics

A monitoring program, including the acquisition of a series of topo-bathymetric surveys and oblique aerial photos, has been carried out at Ancão Inlet since its artificial opening in June 1997. This paper presents morphological and volumetric results, including inlet channel evolution (in terms of width, depth and cross-sectional area) and tidal delta formation. The results are analysed in relation to the prevailing oceanographic conditions. This allows the development of a conceptual evolutionary model for the natural evolution of artificially opened inlets with four stages: Stage 1 is the artificially opened inlet; Stage 2 represents the inlet after reaching dynamic equilibrium for the channel while ebb- and flood-tidal deltas are still developing; Stage 3 is the “mature” migrating inlet; and Stage PS (stage post-storm) is the inlet situation after high-energy conditions. The transition from Stage 1 to Stage 3 is a continuous process with intermediate sub-stages. Transition to Stage PS is a discrete phenomenon, caused by high-energy events, after which the inlet gradually changes back to the previous stage. Ancão Inlet was in Stage 1 in June 1997. In April 1998 the inlet channel reached dynamic equilibrium, thus beginning Stage 2. One year after the opening (July 1998) the inlet showed fully developed ebb and flood deltas, reaching the end of Stage 2. Transition to Stage 3, with the beginning of the downdrift migration and bypassing processes, took place during the second year. Stage PS characteristics were observed in January 1999 after high-energy storm conditions, with strong evidence of landward sediment transport. Although the conceptual model was developed for Ancão Inlet, it is envisaged that it could be applicable to other mixed-energy migrating inlets opened in an artificial way.

Glacier changes in southern Spitsbergen, Svalbard,1901–2000

AbstractHigh-resolution ground-penetrating radar surveys at 50 MHz on the polythermal glaciers Hornbreen, Hambergbreen and several surrounding glaciers in southern Spitsbergen, Svalbard, are presented and interpreted. Accurate positioning was obtained using differential global positioning system (DGPS). Digital elevation models (DEMs) of the bedrock and surface were constructed. Comparison of DGPS data and surface DEMs with data from the topographic mappings from 1936 oblique stereoscopic aerial photographs and from Mission Russe in 1899–1901 shows that the Hornbreen and Hambergbreen surfaces are about 60–100 m thinner today in the upper part than at the beginning of the 20th century. Hornbreen has retreated by 13.5 km from the central part of the front, and Hambergbreen by 16 km. All the fronts of the nearby east-coast glaciers in this area have retreated. The bedrock DEM shows that the Hornbreen and Hambergbreen beds lie at –25 to 25 m a.s.l. The combination of sub-sea-level fronts and increasing steepness of the glaciers suggests that the low-lying glaciated valley filled by Hornbreen and Hambergbreen may become a partially inundated ice-free isthmus within perhaps 100 years.

Precision mapping and interpretation of oblique aerial photographs

Precision mapping and interpretation of oblique aerial photographs

Terrain measurement using automated digital photogrammetry

Introduction Photogrammetry has traditionally provided a means of generating three-dimensional spatial data to represent terrain surfaces, which complements traditional ground-based surveying methods. Although techniques such as airborne laser scanning (Lohr 1998) and synthetic aperture radar (Hogg et al. 1993; Vencatasawamy et al. 1998) have developed, photogrammetry remains the primary method of generating topographic maps (Wolf 1983; Capes 1998). One important advantage of photogrammetry is the flexibility of scale that allows application to imagery acquired from ground, air and space. Indeed, a new generation of high (i.e. 1 m) resolution satellite sensors (Capes 1998) is likely to further increase the potential applications of photogrammetry. Despite many advantages, there have been several problems with the application of photogrammetry using traditional methods. Most significantly, there was the requirement to use an expensive and complex photogrammetric stereoplotter. This ensured that the measurement process was slow and generally required the skills of an experienced operator, particularly if results of the highest accuracy were to be obtained. Rapid developments in computing hardware and software have allowed the science of photogrammetry to develop rapidly during the last ten years (Gruen 1994; Atkinson 1996; Greve 1996). These developments have radically eased many of the problems and limitations associated with traditional analogue instrumentation. Use of a purely numerical or analytical solution provides flexibility, which assists in two important ways. Satellite imagery, oblique aerial photography and ground-based imagery can be used, in addition to the more traditional vertical aerial perspective. Similarly, imagery acquired using

Precision mapping and interpretation of oblique aerial photographs

Precision mapping and interpretation of oblique aerial photographs

Developing rectification programs for small computers

A series of programs, widely known by the name aerial, is available for the rectification of oblique aerial photographs. The programs have developed over many years, in response to users' needs and increasing computer power. In recent years two major modifications have been introduced: a version to rectify raster images under 16-bit versions of Microsoft Windows; and a version with an extended range of facilities to run under 32-bit versions of Windows. The historical development of the programs is described, and the objectives of the most recent versions are explained. The operation of the programs is illustrated with an extended example from recent practice. Copyright © 2000 John Wiley & Sons, Ltd.

New Zealand glacier response to climate change of the past 2 decades

Oblique aerial photography of 111 glaciers during the past 2 decades has recorded a reversal of the past century glacier-recession trend. Cirque glaciers show little response to the recent mass balance increase; mountain glaciers show visible advances. Some valley glaciers have advanced, some have thickened in the upper trunk, and the larger ones and those with proglacial lakes continue to recede. The shift to advance is driven by an average lowering of snowlines of 67 m, equivalent to a cooling of 0.47°C if other factors are held constant.

Restitution analytique informatisée des photographies obliques. Implantation topométrique des structures sur le terrain

Oblique aerial photographs will permit a planimetrical representation of the archaeological structures they have revealed. The perspective of the ground, through computer use, can be restored speedily and accurately. The software created and perfected by Stéphane Laisné using Pascal language, and Basic, is based on a mathematical solution. This technique can be applied to archaeological exploration and also to the photogrammetic survey of excavated sites. The numerical results obtained can be translated into a plan and can reveal the topometrical distribution of structures on the ground before excavation. Accuracy of the values obtained depends mainly on the scale of the photograph, on how precise it is, on ground topography, on topometrical data. Two different and concrete examples are given here.

"Les montagnes qui poussent" ou l'impact des rejets salins des soudières de l'agglomération nancéienne / The 'mountains which rise up' or the impact on the landscape of salt effluents from the soda works of the urban area of Nancy

The aim of the present study is to demonstrate, on the basis of three recent oblique aerial photographs, that the landscape shows the marks of direct and indirect impacts due to the salt effluents produced by the soda works established in the urban area of Nancy. The Solvay and Novacarb soda works are chemical industries producing sodium carbonate from salt and limestone. They have deeply transformed the landscape in the bottom of the Meurthe Valley with the creation of multiple basins for collecting and treating both liquid and solid waste from the soda works. But the impact of these effluents goes far beyond the local context and the resulting disturbances in the drinking water supply of many communes located downstream have caused new, indirect and more extensive modifications to the landscape. The recent project aiming at enlarging the two soda works, and as a consequence of this the increased volume of effluents, have raised a polemic between the industry and the communes using the water from the Moselle River. Diverse solutions for the treatment of salt effluents, all of them involving significant landscape alterations, are now being considered.

Bundle Adjustment For 35 mm Oblique Aerial Photography

The full provision of ground control points for oblique, small format photography used for mapping purposes is uneconomic because each photograph covers a small area of ground. This paper describes the implementation of a bundle adjustment program for 35 mm oblique aerial photography. Image co‐ordinates are measured on enlarged prints, with a digitizing tablet driven by Carto MDSD software, and are then processed with the NLHBUNT program. The measurement system was proved by using vertical standard format photographs of a test block saturated with high quality ground control. Measurements taken with the MDSD system gave acceptable accuracy when compared with a set taken with a Zeiss P3 analytical workstation. A bundle adjustment was then carried out with the MDSD data; the results obtained compared satisfactorily with known ground values. A hand‐held 35 mm Pentax LX camera was flown over the test site and three strips of 1:30 000 scale oblique photography were obtained. Following bundle adjustment, the empirical accuracy of derived co‐ordinates was about 1.5 m in X, 3 m in Y and 2 m in Z. Factors affecting this accuracy are discussed and further developments of the system are proposed.

Steady state behaviour of the black ven mudslide: The application of archival analytical photogrammetry to studies of landform change

AbstractThe concept of dynamic equilibrium has provided geomorphologists with a challenging paradigm for studying landform evolution but quantitative evidence for its existence has proved illusive, particularly for complex geomorphological systems. The authors believe that the principle has now been verified through the application of the ‘archival photogrammetric technique’ to a sequence of historical photographs spanning 50 years of process at the Black Ven mudslide complex in Dorset, U.K.The principles and limitations of the archival photogrammetric technique are described. The method is applied to oblique and vertical aerial photographs of Black Ven at five epochs, commencing in 1946, continuing at approximately 10 year intervals until 1988. The technique is used to generate plans/contours/sections and a dense and accurate digital elevation model (DEM) of the whole site at each epoch. This is used to generate ‘DEMs of difference’ and a ‘distribution of slope angle’ which suggest that the mudslides are in equilibrium despite the removal of 200 000 m3 of sediment between 1958 and 1988. Extrapolation of the slope distribution through time suggests that the frequency of an episodic landform change model at Black Ven may be approximately 60 years.

Anomalous glacier responses to 20th century climatic changes in Darwin Cordillera, southern Chile

AbstractThere is an asymmetric pattern response of glaciers in Darwin Cordillera (54–55° S, 69–71° W) to the climate of the 20th century. This asymmetry is suggested here as a cause of an increased wind activity which has a pronounced orographic effect. Although climatic records for the last 50 years show a warming trend, as well as no trend in precipitation in the area, some glaciers are advancing. The area is characterized by strong climatic gradients, with high rates of precipitation on the southwestern side of the range and dry conditions on the northern side. Glaciers on the northern and eastern sides show a general trend of receding fronts. With a few exceptions, these glaciers have gradually and uninterruptedly been shrinking since the turn of the century. On the southern rim, the present extents of some glaciers are similar to their 20th century maximum extents. These are, in turn, similar or close to the Holocene maximum. The most extreme sites are the glaciers on either side of Mount Darwin, which is 2469 m high. The north-facing glacier Ventisquero Marinelli has retreated several hundred metres per year over the last two decades, while the south-facing glaciers in the Pahia Pia basin have advanced during the same period.In this study, the frontal changes over the last 50 years of 20 glaciers have been analysed. Aerial photographs (verticals) from 1943 and 1984 have been used, as well as oblique aerial photographs from 1993. The general result is that glaciers with accumulation areas facing south and west show somewhat stable fronts, while glaciers facing east and north show receding fronts.

Anomalous glacier responses to 20th century climatic changes in Darwin Cordillera, southern Chile

AbstractThere is an asymmetric pattern response of glaciers in Darwin Cordillera (54–55° S, 69–71° W) to the climate of the 20th century. This asymmetry is suggested here as a cause of an increased wind activity which has a pronounced orographic effect. Although climatic records for the last 50 years show a warming trend, as well as no trend in precipitation in the area, some glaciers are advancing. The area is characterized by strong climatic gradients, with high rates of precipitation on the southwestern side of the range and dry conditions on the northern side. Glaciers on the northern and eastern sides show a general trend of receding fronts. With a few exceptions, these glaciers have gradually and uninterruptedly been shrinking since the turn of the century. On the southern rim, the present extents of some glaciers are similar to their 20th century maximum extents. These are, in turn, similar or close to the Holocene maximum. The most extreme sites are the glaciers on either side of Mount Darwin, which is 2469 m high. The north-facing glacier Ventisquero Marinelli has retreated several hundred metres per year over the last two decades, while the south-facing glaciers in the Pahia Pia basin have advanced during the same period.In this study, the frontal changes over the last 50 years of 20 glaciers have been analysed. Aerial photographs (verticals) from 1943 and 1984 have been used, as well as oblique aerial photographs from 1993. The general result is that glaciers with accumulation areas facing south and west show somewhat stable fronts, while glaciers facing east and north show receding fronts.

Principal variables influencing the integration of agrarian constructions in the landscape

In present paper would be analyzed which are the most important variables that have influence on landscape integration of agricultural constructions. A bibliographic study, an in situ study and an oblique aerial photography study have been carried out for this. Check list of the most important variables that take part on visual impact of agricultural construction have been obtained as a result of this research work.