Tree phenology and carbon dioxide fluxes - use of digital photography for process-based interpretation at the ecosystem scale

Vegetation phenology is an important indicator of climate change and climate variability and it is strongly connected to biospheric–atmospheric gas exchange. We aimed to evaluate the applicability of phenological information derived from digital imagery for the interpretation of CO2 exchange measurements. For the years 2005–2007 we analyzed seasonal phenological development of 2 temperate mixed forests using tower-based imagery from standard RGB cameras. Phenological information was jointly analyzed with gross primary productivity (GPP) derived from net ecosystem exchange data. Automated image analysis provided reliable information on vegetation developmental stages of beech and ash trees covering all seasons. A phenological index derived from image color values was strongly correlated with GPP, with a significant mean time lag of several days for ash trees and several weeks for beech trees in early summer (May to mid-July). Leaf emergence dates for the dominant tree species partly explained temporal behaviour of spring GPP but were also masked by local meteorological conditions. We conclude that digital cameras at flux measurement sites not only provide an objective measure of the physiological state of a forest canopy at high temporal and spatial resolutions, but also complement CO2 and water exchange measurements, improving our knowledge of ecosystem processes.

Cosine Lobe Based Relighting from Gradient Illumination Photographs

We present an image-based method for relighting a scene by analytically fitting cosine lobes to the reflectance function at each pixel, based on gradient illumination photographs. Realistic relighting results for many materials are obtained using a single per-pixel cosine lobe obtained from just two color photographs: one under uniform white illumination and the other under colored gradient illumination. For materials with wavelength-dependent scattering, a better fit can be obtained using independent cosine lobes for the red, green, and blue channels, obtained from three achromatic gradient illumination conditions instead of the colored gradient condition. We explore two cosine lobe reflectance functions, both of which allow an analytic fit to the gradient conditions. One is non-zero over half the sphere of lighting directions, which works well for diffuse and specular materials, but fails for materials with broader scattering such as fur. The other is non-zero everywhere, which works well for broadly scattering materials and still produces visually plausible results for diffuse and specular materials. We also perform an approximate diffuse/specular separation of the reflectance, and estimate scene geometry from the recovered photometric normals to produce hard shadows cast by the geometry, while still reconstructing the input photographs exactly.

Stereocopic Photography Encounters the Staircase

The staircase is presented as the architectural component that most potently embodies thresholds, boundaries and passages due to its diagonal orientation and essence as an intermediary zone. Connections then are made between the kinesthetic requirements of traversing a staircase and viewing a stereoscopic photograph. From this foundation, the haptic essence of stereoscopic photography is proposed as uniquely qualified medium through which to view a staircase and therefore thresholds, boundaries, and passages within architecture. Analyses of stereoviews of staircases in the Palais de Justice in Brussels, the Library of Congress in Washington, and the Palais Garnier (Opéra) in Paris close the essay.

Evaluation of a novel photography-based home assessment protocol for identification of environmental risk factors for falls in elderly persons

PRINCIPLES To evaluate the validity and feasibility of a novel photography-based home assessment (PhoHA) protocol, as a possible substitute for on-site home assessment (OsHA). METHODS A total of 20 patients aged ≥65 years who were hospitalised in a rehabilitation centre for musculoskeletal disorders affecting mobility participated in this prospective validation study. For PhoHA, occupational therapists rated photographs and measurements of patients' homes provided by patients' confidants. For OsHA, occupational therapists conducted a conventional home visit. RESULTS Information obtained by PhoHA was 79.1% complete (1,120 environmental factors identified by PhoHA vs 1416 by OsHA). Of the 1,120 factors, 749 had dichotomous (potential hazards) and 371 continuous scores (measurements with tape measure). Validity of PhoHA to potential hazards was good (sensitivity 78.9%, specificity 84.9%), except for two subdomains (pathways, slippery surfaces). Pearson's correlation coefficient for the validity of measurements was 0.87 (95% confidence interval [CI 0.80-0.92, p <0.001). Agreement between methods was 0.52 (95%CI 0.34-0.67, p <0.001, Cohen's kappa coefficient) for dichotomous and 0.86 (95%CI 0.79-0.91, p <0.001, intraclass correlation coefficient) for continuous scores. Costs of PhoHA were 53.0% lower than those of OsHA (p <0.001). CONCLUSIONS PhoHA has good concurrent validity for environmental assessment if instructions for confidants are improved. PhoHA is potentially a cost-effective method for environmental assessment.

John Garstang at Sirkeli Höyük, Cilician Plain, in 1936-1937: Old Photographs and New Evidence from the Renewed Excavations

During the winter of 1936-1937, British archaeologist John Garstang (1876-1956) excavated several trenches at the site of Sirkeli Höyük, located in the Plain of Cilicia (18 km west of modern-day Ceyhan). After a single campaign, however, he left the site and his interest shifted to site of Yumuktepe/Mersin, where he then excavated for a number of years. Apart from two very brief preliminary reports of his excavations at Sirkeli Höyük, which were published in the journal 'Annals of Archaeology and Anthropology of the University of Liverpool', not much is known about the trenches and their associated finds. Unpublished photographs kept in the Special Archives of University College London shed new light on the location and orientation of some of Garstang’s trenches at the site. Furthermore, in the 2012 campaign of the renewed Turkish-Swiss excavations at the site, a trench was found in the western part of the northern terrace that most probably was excavated by Garstang, but was not mentioned by him in his reports. This hitherto unknown trench may be related to his discovery of a lion-shaped column base made of basalt that is now kept in the collections of the Archaeological Museum of Adana.

Developing a Geographic Information System Index for Historical Aerial Photographs

This paper describes the creation of a GIS database index to the collection of historical aerial photographs of Connecticut housed in the Map and Geographic Information Center in the Homer Babbidge Library at the University of Connecticut. The index allows patrons to search for scanned aerial photograph images for a specific location across multiple years and to retrieve digital scans from the Library server. Procedures for scanning and georeferencing the images, preparing metadata for the images, and creating the GIS database index are described.