Aerial Survey

During 2 years (2001–2003), we performed seasonal aerial surveys in the central Spanish Mediterranean following the transect line methodology in order to determine the abundance and distribution patterns of loggerhead turtles Caretta caretta. We surveyed a total of 16 700 km, accounting for 770 turtle sightings. Loggerhead turtles were present with high abundance all year round. No seasonal differences in abundance were found, except in spring 2001, where the density of turtles was higher than in the other seasons. Our results show that the Western Mediterranean is not a ‘summer’ feeding area as proposed previously, as a high number of turtles are present throughout the year. The average surface density of turtles in the whole study area was 0.21 turtles km−2 [95% confidence interval (CI): 0.17–0.25], and the mean abundance was 6653 turtles (95% CI: 5514–8027). The data relate to the number of turtles on the surface only, as diving turtles escape observation. Correcting our estimations of diving behaviour data in the area, the absolute abundance was 18 954 turtles (95% CI: 6679–53 786). Bearing in mind that around 25 000 loggerheads are caught per year in the Spanish Mediterranean, our results indicate that accidental captures seem to be a significant threat for this species, and conservation measures have to be implemented to avoid a non-sustainable situation.

We investigated the distribution of wild reindeer (Rangifer tarandus tarandus) from aerial surveys in 1986–1998 in 622 contiguous 4-km2 grid squares in relation to density of power lines, roads and ski trails in the Nordfjella region, south-central Norway. Density of reindeer was significantly lower in developed quadrats compared to undeveloped quadrats and decreased with increasing density of development. No reindeer were observed in areas exceeding 1.3 km/km2 of linear structures and only 1.1% of the reindeer were observed in areas exceeding 0.8 km/km2 of linear structures, an area constituting 17% of the study area. The results imply that development, and also the degree of development, affect the availability of range for wild reindeer. Furthermore, the results suggest that reindeer may abandon areas once disturbance exceeds a critical level. We conclude that there is a need for cumulative impact assessments of the overall development in Norwegian mountain regions, to preserve the last remaining wild reindeer populations in Europe.

Bias, precision and accuracy have been studied extensively in wildlife population estimation including aerial surveys. A review of the literature shows that the concepts of bias and precision are used broadly consistently. Aerial survey data from known populations of feral pig carcases and white-tailed deer show that few density estimates are unbiased and precise. Research is needed, however, to clarify how much bias and how much precision are enough for the various types of wildlife management activities. Accuracy is used in two closely related but different ways. One set of definitions of accuracy relates to deviations from the true value (bias) and the second set relates to squared deviations from the true value (bias and precision). The implications are that authors are encouraged to clearly state which definition of accuracy they use, or focus solely on bias and precision.

Abstract A lack of reliable observations for canopy science research is being partly overcome by the gradual use of lidar remote sensing. This study aims to improve lidar-based canopy characterization with airborne laser scanners through the combined use of lidar ...

Aerial photography is one of the most important and cost-effective ways of recording traces of the past and discovering new sites. It also offers the archaeologist an alternative viewpoint on these archaeological traces, and is one of the most exciting and challenging types of fieldwork. The experiences of the contributors to this volume highlight the role that bias, subjectivity and perception play in the shaping of flights and in the results themselves. They draw on important aspects of archaeological fieldwork such as experience, intuition, improvisation, emotion and stress, which are all too often left unarticulated. These contributions from the practitioners, photographers and interpreters that from the aerial archaeological community present a counterpoint to the traditional textbook.

There are different natural hazard, among these different natural hazards flood are most devastating and frequently occurring calamities taking human lives and causing economic damages. This report has been prepared to present hazard analysis mapping of flood of Punyamata River as a project work of 4th year student. The main focus of this project work was to determine the Elements at risk of the Punyamata River and to create flood hazard zone mapping of following years return period (5, 10, 20, 50, and 100). This project work explores the element at risk of the study area. The user’s requirement is extracted by experts view in qualitative way and system requirements are extracted by practice. Data requirement for flood hazard mapping are extracted from expert’s view and literatures. The hazard class map was performed by flood simulation process. Contours can be extracted from the system for Digital Elevation Model (DEM). The hazard map of various years return period and effected buffer zones are the main outputs from the system.

This paper represents the first systematic research about the Late Iron Age site of El Espinillo ever published. The site is located in the Spanish province of Burgos, regional council of Castilla y León, in the municipality of Villadiego, and nearby the villages of Villadiego and Villalibado. This work presents an approach to the scarce historiography and aims to highlight the singularity of such site within the regional settlement pattern. The research about El Espinillo has been carried out by means
of non-destructive techniques as artefactual survey and aerial  hotography detection. These allow us to present some conclusions and future work idea for a major understanding of the settlement pattern and the exploitation strategies during the Late Iron Age in the Iberian northern Plateau.

This report documents the results of a Systematic Reconnaissance Flight (SRF) aerial survey of the Malagarasi-Muyovozi Ramsar Site (Tanzania), conducted from 17
to 28 November 2001. The survey was made as part of the Danida-funded project on Sustainable and Integrated Management of the Malagarasi-Muyovozi Ramsar Site
(SIMMORS), which aims at assisting the Wildlife Division of the Ministry of Natural Resources and Tourism to fulfil its obligations under the Ramsar Convention on Wetlands.
The aerial survey provided a successful rapid assessment of the status and distribution of wildlife, vegetation & wetland types and their status in the Malagarasi-Muyovozi Ramsar
Site. The present report only presents the results of the observations on the status of the vegetation, disturbances and threats to habitats from human activities in the Ramsar Site. The types and extent of different vegetation types, human activities, threats and buffer zone issues in this important wetland area are discussed.

Technical Report for the Project on Sustainable and Integrated Management of the Malagarasi-Muyovozi Ramsar Site (SIMMORS), 2001.

Wetland extent was mapped for the central Amazon region, using mosaicked L-band synthetic aperture radar (SAR) imagery acquired by the Japanese Earth Resources Satellite-1. For the wetland portion of the 18×8° study area, dual-season radar mosaics were used to map inundation extent and vegetation under both low-water and high-water conditions at 100-m resolution, producing the first high-resolution wetlands map for the region. Thematic accuracy of the mapping was assessed using high-resolution digital videography acquired during two aerial surveys of the Brazilian Amazon. A polygon-based segmentation and clustering was used to delineate wetland extent with an accuracy of 95%. A pixel-based classifier was used to map wetland vegetation and flooding state based on backscattering coefficients of two-season class combinations. Producer's accuracy for flooded and nonflooded forest classes ranged from 78% to 91%, with lower accuracy (63–65%) for flooded herbaceous vegetation. Seventeen percent of the study quadrat was occupied by wetlands, which were 96% inundated at high water and 26% inundated at low water. Flooded forest constituted nearly 70% of the entire wetland area at high water, but there are large regional variations in the proportions of wetland habitats. The SAR-based mapping provides a basis for improved estimates of the contribution of wetlands to biogeochemical and hydrological processes in the Amazon basin, a key question in the Large-Scale Biosphere–Atmosphere Experiment in Amazônia.

Researchers studying Dall's sheep (Ovis dalli dalli) associated with a large mineral lick on Dry Creek in the central Alaska Range south of Fairbanks, Alaska, USA, claimed that removal of nearly all mature males by intensive harvest of three-quarter curl or larger males by hunters during the 1980s resulted in accelerated mortality of young males and low productivity in female

Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus) in Europe. Roads, railroads, and power lines have fragmented the original population into 26 separate herds. The reindeer populations are regulated directly according to availability of winter forage. These winter ranges, generally at lower elevations, are however, often subjected to development. Effects of infrastructure and associated human activity on the distribution of wild reindeer during winter were investigated in the Nordfjella mountain region of western Norway. Systematic aerial surveys of the distribution of ca. 2500 reindeer were conducted during late winter 1986–1998. Areas within 2.5 km from power lines were used less than available in 6 of the 8 sampling years, and areas beyond this zone more than expected. Density of reindeer was 79% lower within 2.5 km from power lines compared with background areas, and increased with increasing distance from infrastructure for comparable habitat. Available forage in terms of lichen cover declined 15–30-fold with distance, and was lowest in the undisturbed areas with the highest density of grazing animals. Areas within 5 km from resorts or from roads and power lines in combination were avoided in all years. Continued construction of roads, power lines and cabin resorts endanger these available winter ranges, and hence the long term survival of the population.

Insects are important forest disturbance agents, and mapping their effects on tree mortality and surface fuels represents a critical research challenge. Although various remote sensing approaches have been developed to monitor insect impacts, most studies have focused on single insect agents or single locations and have not related observed changes to ground-based measurements. This study presents a remote sensing framework to (1) characterize spectral trajectories associated with insect activity of varying duration and severity and (2) relate those trajectories to ground-based measurements of tree mortality and surface fuels in the Cascade Range, Oregon, USA. We leverage a Landsat time series change detection algorithm (LandTrendr), annual forest health aerial detection surveys (ADS), and field measurements to investigate two study landscapes broadly applicable to conifer forests and dominant insect agents of western North America. We distributed 38 plots across multiple forest types (ranging from mesic mixed-conifer to xeric lodgepole pine) and insect agents (defoliator [western spruce budworm] and bark beetle [mountain pine beetle]). Insect effects were evident in the Landsat time series as combinations of both short- and long-duration changes in the Normalized Burn Ratio spectral index. Western spruce budworm trajectories appeared to show a consistent temporal evolution of long-duration spectral decline (loss of vegetation) followed by recovery, whereas mountain pine beetle plots exhibited both short- and long-duration spectral declines and variable recovery rates. Although temporally variable, insect-affected stands generally conformed to four spectral trajectories: short-duration decline then recovery, short- then long-duration decline, long-duration decline, long-duration decline then recovery. When comparing remote sensing data with field measurements of insect impacts, we found that spectral changes were related to cover-based estimates (tree basal area mortality [R2adj=0.40, F1,34=24.76, P<0.0001] and down coarse woody detritus [R2adj=0.29, F1,32=14.72, P=0.0006]). In contrast, ADS changes were related to count-based estimates (e.g., ADS mortality from mountain pine beetle positively correlated with ground-based counts [R2adj=0.37, F1,22=14.71, P=0.0009]). Fine woody detritus and forest floor depth were not well correlated with Landsat- or aerial survey-based change metrics. By characterizing several distinct temporal manifestations of insect activity in conifer forests, this study demonstrates the utility of insect mapping methods that capture a wide range of spectral trajectories. This study also confirms the key role that satellite imagery can play in understanding the interactions among insects, fuels, and wildfire.

Castles, often built on hills with extremely steep slopes, or on sea cliffs overlooking stretches of water, were difficult to conquer. Construction techniques and geomorphology of the area were a key factor in making castles impregnable to sieges of military troops or bands of pirates or robbers. Today, the same characteristics make them difficult to survey. In fact, there are huge difficulties in surveying fortified structures on the top of hills or on the edge of a precipice. Such geomorphological features sometimes make the survey difficult, time consuming and expensive and unsafe for operators. Today, these prob- lems can be reduced through the use of drones and photogrammetric processing tools which are based on Structure from Motion algorythms and are easy to use. This method allows us to acquire data with geometric resolution in order to map and study masonry characteristics, as well as analyze and monitor decay and crack patterns for restoration purposes. In this paper, we will discuss the potential of drones and modern photogrammetry techniques in architectural surveys and applied to three case studies. These include the castle of Isabella Morra in Valsinni (Basilicata, South Italy), perched on a cliff; the medieval citadel of Uggiano in Ferrandina (Basilicata, South Italy) in an advanced state of degradation and on a plateau with high geological risk; and the San Fernando Fuerte to Bocochita (Cartagena de Indias, Co- lombia) overlooking the sea.

Pronghorn (Antilocapra americana) abundances commonly are estimated using fixed-wing surveys, but these estimates are likely to be negatively biased because of violations of key assumptions underpinning line-transect methodology. Reducing bias and improving precision of abundance estimates through use of detection probability and mark-resight models may allow for more responsive pronghorn management actions. Given their potential application in population estimation, we evaluated detection probability and mark-resight models for use in estimating pronghorn population abundance. We used logistic regression to quantify probabilities that detecting pronghorn might be influenced by group size, animal activity, percent vegetation, cover type, and topography. We estimated pronghorn population size by study area and year using mixed logit-normal mark-resight (MLNM) models. Pronghorn detection probability increased with group size, animal activity, and percent vegetation; overall detection probability was 0.639 (95% CI ¼ 0.612–0.667) with 396 of 620 pronghorn groups detected. Despite model selection uncertainty, the best detection probability models were 44% (range ¼ 8–79%) and 180% (range ¼ 139–217%) greater than traditional pronghorn population estimates. Similarly, the best MLNM models were 28% (range ¼ 3–58%) and 147% (range ¼ 124–180%) greater than traditional population estimates. Detection probability of pronghorn was not constant but depended on both intrinsic and extrinsic factors. When pronghorn detection probability is a function of animal group size, animal activity, landscape complexity, and percent vegetation, traditional aerial survey techniques will result in biased pronghorn abundance estimates. Standardizing survey conditions, increasing resighting occasions, or accounting for variation in individual heterogeneity in mark-resight models will increase the accuracy and precision of pronghorn population estimates.

La pratique archeologique a beaucoup changee avec l'arrivee de nouvelles techniques et de nouvelles approches intellectuelles. Les outils informatiques, comme le SIG, habituellement utilises par les geographes peuvent ouvrir des perspectives innovantes, a condition que les archeologues integrent leur reflexion dans une demarche de "longue duree" avec une attention a la qualite et a la nature des informations traitees. Les techniques ne doivent pas etre separes d'une reflexion epistemologique. C'est ce que propose l'archeogeographie en ayant une vision analytique et critique des objets geo-historiques. Afin d’exposer l'etat de ces questions en Roumanie, nous avons replace les travaux recents dans l'histoire de la "carte archeologique nationale" roumaine. Puis, cinq exemples d'analyses de sites historiques et archeologiques autour de la basse vallee du Danube proposent cinq thematiques de recherche parmi d’autres dans le domaine de la co...

Giraffes Giraffa camelopardalis are megafaunal browsers and keystone species in African savanna ecosystems. Range-wide population declines are suspected, but robust data are lacking. Tanzania holds the largest population of giraffe of any range state, and aerial surveys constitute most of Tanzania's giraffe population monitoring data, but their accuracy has not yet been assessed. An IUCN status assessment for giraffe is currently underway, and calibrating aerial surveys with ground-based surveys can quantify accuracy of the aerial surveys to ensure more reliable estimates of populations nationwide. We estimated giraffe density and abundance in the Tarangire Ecosystem in northern Tanzania using 2 ground survey methods, distance sampling and capture-mark-recapture, and compared our ground-based estimates with those from the most recent aerial survey in 4 sites. We found aerial survey estimates were biased low, while ground-based surveys were more precise and cost less. We computed correction factors to improve the accuracy of aerial surveys and suggested ways to further improve aerial survey methods.