Historical Aerial Photographs Research Articles

Evolution of the dynamics of Airdrop Glacier, western Axel Heiberg Island, over a seven-decade-long advance

Various remotely sensed data, including historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery, and synthetic aperture radar data, were used to undertake the first comprehensive reconstruction of the dynamics of Airdrop Glacier on Axel Heiberg Island, Nunavut. Observations show a continuous terminus advance totalling ∼6 km since 1950 and notably less variability in its surface velocities in comparison to adjacent Iceberg Glacier. This advance is concurrent with relatively high flow rates over its entire surface, resulting in significant thickening near the terminus and thinning at higher elevations. Velocities have more than halved from the mid-2000s to 2021, but without any definitive evidence of previous flow instabilities, we cannot confirm whether Airdrop's behaviour is cyclic in nature and therefore characteristic of a surge. Instead, Airdrop Glacier could be experiencing a delayed response to the positive mass balance conditions of the Little Ice Age, which could also explain the advance of other nearby glaciers. Its recent slowdown could then be indicative of a gradual adjustment to recent climatic conditions. This study highlights the need for comprehensive studies of glacier dynamics in the Canadian Arctic to improve our understanding of the factors triggering dynamic instabilities and causing the observed variety of behaviours.

Effects of Topography on Vegetation Recovery after Shallow Landslides in the Obara and Shobara Districts, Japan

Intense rainfall-induced shallow landslides can have severe consequences, including soil erosion and vegetation loss, making in-depth research essential for disaster risk management. However, vegetation recovery processes after shallow landslides and their influencing multivariate factors are not well known. This study aims to address this gap by investigating the vegetation recovery processes after shallow landslides and the impact of topography on this recovery. We focus on two regions in Japan: the Shobara district in Hiroshima Prefecture and the Obara district in Aichi Prefecture. The Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) derived from long-term Landsat images, as well as aerial photographs and environmental datasets, are used to measure vegetation recovery. Then, statistical analysis and the Seasonal Autoregressive Integrated Moving Averages (SARIMA) model were employed to investigate the dynamic response of vegetation under different combinations of environmental conditions using NDVI and EVI time series. Historical aerial photographs and vegetation index trend analysis suggest that vegetation in the study areas will take more than ten years to return to a stable state. The results also demonstrate the influence of atmospheric and land cover conditions when monitoring vegetation response using NDVI and EVI. In Obara, concave and convergent terrain positively influenced NDVI, while non-steep, low-elevation, and north-facing terrain positively influenced EVI. In Shobara, gentle and northwest-facing slopes were positively correlated with NDVI, and gentle and west-facing slopes were positively correlated with EVI. SARIMA modeling found that NDVI is more suitable for modeling the middle and late stages of vegetation recovery within 10–25 years after the landslide. In comparison, EVI is better for modeling the early stage of vegetation recovery within 10 years after the landslide.

Glacier, permafrost and thermokarst interactions in Alpine terrain: Insights from seven decades of reconstructed dynamics of the Chauvet glacial and periglacial system (Southern French Alps)

AbstractThis study analyses the long‐term dynamics in the Chauvet glacial and periglacial system (southern French Alps) over seven decades (1948–2020), where several lake outburst floods have been documented since 1930. To accurately describe and explain the complex dynamics of this site, our multidisciplinary approach combines (1) photogrammetry of historical aerial photographs and modern high‐resolution satellite and UAV images, (2) geophysical surveys and (3) geomorphological mapping. We provide evidence for spatial and functional interactions between glacial and periglacial features, especially in the lower sector where different landforms with variable ice‐ and debris‐content and specific dynamics are interplayed. We found the highest thinning rates on ice‐rich terrain located in the central part of the valley bottom, which, together with bedrock morphology, most probably determine the location of the thermokarst. We also documented an overall acceleration of the creeping of the landforms after the 2000s, with a flow direction largely oriented towards the thermokarst depression. The outburst water flowed through a conduit whose successive opening and closure seem to mainly depend on the rate of lateral convergence of left‐ and right‐hand landforms and on the rate of ice melting (and roof collapse) along the conduit walls. Today, the site of Chauvet still represents a potential hazard for the region due to the large water storage capacity (up to 180 000 ± 450 m3) and the development of a predominantly bucket shape in the thermokarst sector.

Changes in the wild bee community (Hymenoptera: Apoidea) over 100 years in relation to land use: a case study in a protected steppe habitat in Eastern Austria

The wild bee community of a sand steppe habitat in Eastern Austria was surveyed in the years 2018 and 2019, complemented with historical data from over 100 years, and analyzed in relation to land use change. The mapping of land use categories was based on historical aerial photographs and orthophotos. Changes in bee community composition were analyzed by a multivariate statistical approach and took ecological traits into account (lecty, nesting type, habitat requirements, flight period, parasitism). In total, 310 bee species were recorded in the area, with the oldest records dating back to 1882. The bee species composition differed significantly among four defined time periods. Across the two most intensively sampled time periods (1931–1966 vs 2001–2021), a decline in species richness of over 50% was observed. We observed a disproportionally high decline of steppe- and sand-associated species, and a distinct shift from ground nesting species to above-ground nesting species. The area covered with woods increased from 1966 to 2018, while the total area covered with grassland and fallows decreased slightly between 1966 and 1994. The oligolectic species assemblage was specialized on Dipsacaceae, Brassicaceae and Fabaceae in the two earlier periods, and on Asteraceae and specifically on Carduoideae during the two later ones.Implications for insect conservationstronger reference to historic land management practices as short time periods of intensive grazing and small-scaled, staggered mowing would be desirable to improve the habitat quality. More drastic measures, such as removal of the topsoil in some parts and changes in the landscape re-establishing exposure to wind erosion, might be necessary, if the area is to be fully restored to the condition it was in a century ago.

National-scale imperviousness mapping and detection of urban land changes

With high land take for urbanization a serious concern, the European Union and Member States have set quantitative targets for limiting land take in Europe. Consistent and reliable information on land take is crucial for measuring progress in achieving these targets. In the big data era, Earth observation data offers opportunities to regularly and consistently monitor land use change dynamics on a national scale. However, often-used methods such as image classification do not solve the mixed pixels problem common to urban areas with high heterogeneity. Moreover, the urban land use changes detected by these methods are often affected by random noise caused by non-relevant changes in atmospheric conditions, sun angle, vegetation phenology, etc. Therefore, the resulting products are often judged as being of insufficient quality for operational application.In this study, we present an approach to measuring annual land take using imperviousness mapping and change detection. Based on the Google Earth cloud computing platform, we first applied a data mining approach on annual Sentinel-2 image scenes to extract temporal and spectral information at Germany wide scale. Then spectral unmixing algorithm was used to estimate sub-pixel fractions of imperviousness. We end by using imperviousness changes to detect newly built surfaces. The change detection products were validated using high-resolution historical aerial photos and images. The results achieved an accuracy of 87% for detecting new built-up and 98% for detecting changes. The difference between the two numbers is caused by the areas with changes on the surface but not for urban use.We found that the integration of temporal information improves the performance of spectral unmixing than using spectral information alone, because it can better distinguish imperviousness from other land covers with similar spectral signatures but different temporal characteristics. We also found that, due to the sub-pixel analysis approach, spectral-unmixing-derived imperviousness is sensitive to urban features even with a size of just a few pixels. Moreover, the imperviousness layer represents urban land with a continuous index, meaning that random noise, represented as a low-range change of fractions, can be filtered out. Our study demonstrated that remote sensing products can be tailored to fulfil the needs of specific applications supporting sustainable land-use policy. This opens up more possibilities for the diverse and growing user communities of urban land change products.

Historical disconnection from floodplain alters riparian forest composition, tree growth and deadwood amount

Riparian forests are among the most dynamic but threatened terrestrial ecosystems. Their dynamism and conservation depend on historical changes in river geomorphology, which can be evaluated through changes in channel sinuosity. However, we lack long-term assessments on sinuosity and how they impact riparian forest composition, tree growth and deadwood amount. To fill this research gap, we reconstructed river sinuosity in 14 sites across the middle Ebro basin, north-eastern Spain, using historical aerial photographs taken in 1927, 1956, 1998–2003 and 2014–2015. Relationships between sinuosity, stand composition and deadwood amount and decay degree were calculated. We also reconstructed radial growth of the major tree species (Populus alba, Populus nigra, Fraxinus angustifolia, Salix alba and Ulmus minor) in two sites to evaluate how coupled it was with changes in river flow after dam building. From 1927 to 2015, sinuosity decreased passing from 1.39 to 1.20. The river dynamics were altered in the 1950s and 1960s after dam and dyke building. Sites with high sinuosity values in 1956 corresponded to mature stands with large P. nigra individuals. Sinuosity was negatively related to F. angustifolia (rs = −0.83, p < 0.001) and P. alba (rs = −0.64, p = 0.02) abundance, whereas sites dominated by P. alba and U. minor presented abundant decayed deadwood. A loss of sinuosity and a contraction of the riverbank gradient increased disconnection of active channel from floodplain, with a mixing of more (e.g., P. nigra) and less phreatophytic species (e.g., U. minor). River flow diversion reduced growth and increased the tree-to-tree P. alba growth coherence. Hydrological droughts contributed to growth decline and dieback of U. minor, which is sensitive to spring river flow. Conservation and restoration of riparian forests must consider historical changes in river geomorphology related to human activities.

Tájalakulási folyamatok és a növényzet változása a Gödi-lápréten

The natural values of the fens and moorgrass meadows at Göd became known in the 1980s. The area of almost 70 hectares, previously used for centuries as pasture and meadow, has been isolated by urbanisation and land use has changed over the last three decades, with the ploughing up and conversion into a golf course and the designation of part of the valuable fen and Molinia meadows as nature reserves. These protected areas are well studied from a botanical point of view, even on a national scale, and the trends in vegetation change incet he 1990s are therefore well understood. The aim of this article is to provide a historical overview of the landscape change in the fen and to explore the changes in flora and habitats. The research involved the analysis of historical maps and archival aerial photographs, the evaluation of flora lists from three botanical surveys carried out at 15-year intervals and a comparative analysis of habitat maps using GIS. The results show that the water regime of the studied wetlands is changing, the vegetation is degraded and becoming poorer in fen specialists, while at the same time the increase in habitat diversity has led to an enrichment of the fauna of the studied area.

Multi-decadal erosion rates from glacierized watersheds on Mount Baker, Washington, USA, reveal topographic, climatic, and lithologic controls on sediment yields

Understanding land surface change in and sediment export out of proglacial landscapes is critical for understanding geohazard and flood risks over engineering timescales and characterizing landscape evolution over geomorphic timescales. We used automated Structure from Motion software to process historical aerial photographs and, with modern lidar data, generated a high-resolution DEM time series with coverage over 10 glacierized watersheds on Mount Baker, Washington, USA for the time period between 1947 and 2015. We measured basin-wide sediment yields and sediment redistribution on hillslopes and in stream channels. Slopes within most measured erosion sites are above theoretical and observed debris-flow thresholds. We observed significant erosion of hillslopes and limited deposition on hillslopes and in stream channels. Sediment delivery ratios during time periods with net erosion averaged 0.73. We determined, consistent with previous field observations, that debris flows originating from moraines are a primary erosion mechanism in proglacial zones on Mount Baker. Time series measurements indicate that temporal variability in erosion rates is associated with climate oscillations, with higher erosion rates during cooler-wetter periods. Basin-wide sediment yield is positively correlated with lithology (r2 = 0.54), hillslope angle (r2 = 0.52), drainage area (r2 = 0.82), and negatively correlated with stream channel slope (r2 = 0.67). Topographic differences between high and low yielding basins indicate that spatial variability in erosion on Mount Baker is sensitive to Pleistocene and Holocene glacial and volcanic activity. Specific sediment yields in six basins averaged 4600 ton/km2/yr, consistent with global measurements in glacierized catchments. Specific sediment yield decreased with increasing basin area, with total loads in the downstream main stem Nooksack River estimated between 480 and 820 ton/km2/yr. Proglacial sediment yields account for between 18 and 32 % of total sediment load in the main stem Nooksack River and exceed contributions by bluff and terrace erosion, which account for between 8 and 13 % of total load. Our findings indicate that erosion in glacierized basins is sensitive to decadal climate oscillations and that high proglacial sediment yields provide an important contribution to river systems downstream, particularly in catchments where upland topography and lithology is favorable.

Identification of Abandoned Logging Roads in Point Reyes National Seashore

Temporary roads are often placed in mountainous regions for logging purposes but then never decommissioned and removed. These abandoned forest roads often have unwanted environmental consequences. They can lead to altered hydrological regimes, excess erosion, and mass wasting events. These events can affect sediment budgets in streams, with negative consequences for anadromous fish populations. Maps of these roads are frequently non-existent; therefore, methods need to be created to identify and locate these roads for decommissioning. Abandoned logging roads in the Point Reyes National Seashore in California, an area partially under heavy forest canopy, were mapped using object-based image processing in concert with machine learning. High-resolution Q1 LiDAR point clouds from 2019 were used to create a bare earth model of the region, from which a slope model was derived. This slope model was then subjected to segmentation algorithms to identify and isolate regions of differing slopes. Regions of differing slopes were then used in a convolutional neural network (CNN), and a maximum likelihood classifier was used to delineate the historic road network. The accuracy assessment was conducted using historic aerial photos of the state of the region post-logging, along with ground surveys to verify the presence of logging roads in areas of question. This method was successfully able to identify road networks with a precision of 0.991 and an accuracy of 0.992. It was also found that the CNN was able to identify areas of highest disturbance to the slope gradient. This methodology is a valuable tool for decision makers who need to identify areas of high disturbance in order to mitigate adverse effects.

DIGITISATION OF RETREATING INDUSTRIAL HERITAGE; MODELLING THE DECOMMISSIONING OF THE COAL WASHERIES OF ONLLWYN

Abstract. Digitisation for the purposes of recording cultural heritage and its condition is conventionally associated with the task of documentation for conservation. Occasionally emergency recording will anticipate the potential imminent destruction of heritage at risk. By contrast here, although the heritage status of the site whilst proposed in the 1990s, it was never secured yet the closure and eventual dismemberment of the buildings is a plan that is already underway. The coal washeries of Onllwyn sit within a vast landscape that is now most widely recognised as a National Park. During the last century, however, it was a thriving industrial site. The assembly of buildings used to wash and sort coal prior to distribution were recorded using a terrestrial laser scanner and an aerial drone in August 2022 shortly prior to the closure of a site that had been part of a changing industrial landscape since the mid-nineteenth century. As part of a wide agreement to build a historic narrative for a once large industrial site with a planned closure a comprehensive historical review has been built. This included the acquisition of historic maps but also of numerous historical aerial and terrestrial photographs as well as the collation of films and oral histories. Here pointclouds generated from terrestrial laser scans, photogrammetry from drone imagery and photogrammetry from historical aerial images have been combined in an attempt to create a navigable digital backdrop to the decommissioning of a vast industrial landscape as it anticipates a new future. The aim of the models created is to provide a virtual spatial platform to co-locate memories of a community life that is left centred around a lost place of work.

Mapping the impacts of coastal erosion on the heritage assets of Ynys Enlli (Bardsey Island), North Wales, UK

Coastal erosion and sea level rise has become a significant threat to coastal heritage due to climate change. Management bodies are monitoring the risks posed by undertaking studies, ranging from Rapid Coastal Zone Assessments to much larger government and research council funded studies. These studies have incorporated varying techniques and datasets such as environmental sampling, LiDAR, GPS, and UAV surveys. However, these approaches rarely combine study of historic shoreline change with physical susceptibility modeling. This paper presents a combined methodology, utilizing LiDAR and survey data collected by the Climate, Heritage, Environments of Reefs, Islands and Headlands (CHERISH) project, along with historic mapping and aerial photography to produce a risk assessment for the heritage assets located on Ynys Enlli (Bardsey Island), North Wales. By constructing an Historic Erosion Model and an Erosion Susceptibility Model using ESRI’s ArcGIS 10.5.1. with the DSAS Plugin and combining them with the LiDAR-derived spatial extents of archaeological features on the island, this project has shown that using both methodologies alongside each other can create a more complete overview of coastal environment change for the creation of vulnerability indexes.

Archaeology of a Rural Qanāt: Water Management and Social Relations in 17th Century Isfahān, Iran

This study investigates the water management structures and social relations that centred around a specific qanāt line in a rural setting in Iran during the Safavid period, specifically in the mid-17th c. CE. The setting is northwest of Isfahān, near Varkān, at a site called Mobārrak Ābād. The method combines analysis of documentary evidence and remote sensing of historical aerial photography. The documentary evidence provides administrative details of a suyūrghāl grant to Mohammad Beig E’temād-al-Dowleh by Shah ‘Abbās II. In combining this with the physical characteristics of the qanāt of Mobārrak Ābād, as derived from the aerial photograph, I provide identification and analysis of the two canals providing water beyond the garden and the use of the water derived from the qanāt for agricultural irrigation and in Aranjon’s village infrastructure. The conclusions discuss the material conditions in the periphery of the prosperous and fertile Isfahān region and provide a relative dating to the qanāt and associated infrastructure. The personal and social relations that can be derived from this evidence are relations of personal and economic dependency between Mohammad Beig E´temād-al-Dowleh and the Shah on the one hand, as well as the labour relations between the peasant population living with and from the qanāt who maintain this infrastructure and the administrative superstructure on the other. The article thus provides new insights into an under-investigated subject and region in the period.

Fire Cycles and the Spatial Pattern of the Scrub–Sedgeland Mosaic at Blakes Opening in Western Tasmania, Australia

The cause of large areas of treeless Sedgeland and Scrub communities in western Tasmania, one of the wettest regions of Australia, has long puzzled ecologists, given the climatic suitability for temperate Eucalyptus and rainforests. A pervasive theory, known as the ecological drift model, is that landscape fires have created a dynamic mosaic of fire-adapted and fire-sensitive vegetation. A contrary view, known as the fire cycle model, asserts that fire patterns are a consequence, not a cause, of the mosaics, which are edaphically determined. We leveraged the opportunity presented by a large wildfire that occurred in a Sedgeland tract surrounded by Eucalyptus forest in the Huon Valley in 2019 to help discriminate between these competing models. Specifically, we sought to determine whether there was any evidence that the Sedgeland was becoming infilled with Scrub prior to the 2019 fire, and whether the fire caused the Scrub community to convert to Sedgeland. A field survey was used to assess the mortality of shrubs and their regeneration following the 2019 fire, and we used dendrochronology to determine the age of the fire-killed shrubs. We also used historical aerial photography since the 1980s to map fire scars and the distribution of Sedgeland and Scrub. We found that fire killed most shrubs in the Sedgeland and Scrub communities and initiated a cohort of shrub regeneration. Dendrochronological analysis of the fire-killed shrubs revealed that most were established approximately 40 years ago, following a fire that is apparent from aerial photography and most likely occurred around 1983. An analysis of aerial photography revealed that since 1980, the distribution of the Scrub community has remained stable, although the density of shrubs declined following the 1983 fire. The recovery of the burned Scrub areas in 1983 and the rapid regeneration of the shrubs following the 2019 fire is more consistent with the fire cycle model than the ecological drift model. These findings concord with the demonstrated stability of the Eucalyptus forest boundary at this site revealed by a separate study. The slow growth of the shrubs cautions against frequently burning Sedgelands, because it could cause the collapse of shrub populations by killing the immature cohort initiated by fire.

Combining historical aerial photography with machine learning to map landscape change impacts on dry grasslands in the Central Alps

ContextStriking land-use changes after WW II characterize the past century in the European Alps with impact on ecosystems and biodiversity. Documenting land-use changes is often difficult due to limited information from the past. Mapping landscape history with aerial photography can foster the understanding of human-induced changes in vulnerable ecosystems, such as the remnants of dry grasslands in the Central Alps.ObjectivesWe aimed to assess changes in grassland vegetation and their current extent in Val Venosta (European Alps, Italy) in relation to overall landscape settings, anthropogenic drivers of change and the effectiveness of the protected areas.MethodsWe performed a land-cover classification based on a mixed machine learning approach including several auxiliary classifiers in a random forest model to characterise the extent and state of (dry) grasslands. We calculated landscape metrics between 1945 and 2015 to assess shape-related changes, especially regarding their landscape embedding and the protection status of sites.ResultsThree main processes related to a changing extent in grassland habitat prevail: (i) agricultural intensification, (ii) settlement expansion at the valley bottom and (iii) forest expansion (afforestation and encroachment due to decreasing pasture activities) on the valley slopes. The remaining grassland habitat is increasingly isolated and fragmented, leaving only few core areas of dry grassland, which tended to be better conserved within protected areas.ConclusionThe changes in extent of dry grasslands revealed marked changes. Transformations are assumed to be predominantly caused by human impact and successional changes. Our results confirm the importance of protected area networks. The pronounced landscape changes underline the urgent need for future research with explicit focus on the changes at community level and the underlying causes. Identifying all relevant drivers of change should be a key element in targeted conservation efforts.

Multiple Aspects of the Fight against the Red Palm Weevil in an Urban Area: Study Case, San Benedetto del Tronto (Central Italy).

The fight against alien invasive insect pests of plants in the urban environment often affects varied sectors of the economy, landscape gardening, public health, and ecology. This paper focuses on the evolution of the red palm weevil in San Benedetto del Tronto, a coastal urban area in central Italy. We investigated the evolution of this insect pest of palm trees in the 2013-2020 period, considering both the effectiveness of the chemicals used and their potentially harmful effects. With a multidisciplinary approach, we carried out a spatio-temporal analysis of the extent and mode of pest spread over time using historical aerial photos, freely available remote sensing images, and field surveys integrated in a GIS environment. We also assessed the toxicity risk associated with the chemicals used to protect the palms from the red weevil. The fight against this weevil is now concentrated in specific areas such as parks, roads, villas, hotels, farmhouses, and nurseries. The preventive chemical treatments applied are very effective in preserving the palms, but they show a toxic potential for all organisms. We discuss current local management of this pest, focusing on several aspects involved in the fight against this beetle in an urban area.

Detecting the imprints of past clear‐cutting on riparian forest plant communities along a Mediterranean river

AbstractIn riparian forests, clear‐cutting causes long‐lasting changes in both riparian and aquatic biota. In this work, we examined if past clear‐cutting events occurred at different times have imprints on riparian forests in a Mediterranean river in central Italy. We carried out a randomized, plot‐based vegetation survey of riparian forests in systematically sampled 500 m‐long sectors along the whole river, dividing the riparian zone into two internal and two external strips. From historical aerial photos, past clear‐cutting events within plots were detected and classified in age classes: (i) cut in the past 8 years (recent); (ii) cut between 8 and 19 years ago (intermediate); (iii) no signs of clear‐cutting in the last 19 years (distant). We analyzed the responses of vegetation to clear‐cutting and strip position. Alien species richness was higher and woody species richness was lower in recently clear‐cut areas compared to those with a distant clear‐cutting event. Moreover, recently cut woods had more alien and synanthropic species. Intermediate clear‐cut areas had higher levels of invasion by alien species compared to areas with distant cut. Riparian forests of internal strips are impacted by clear‐cutting, but seem to recover in 8–19 years thanks to their natural resilience. Conversely, recent or intermediate clear‐cutting events did not affect any of the investigated vegetation attributes in the external strips since such forests were already invaded by alien and synanthropic species after human disturbance. Our results confirm that clear‐cutting events can have long‐lasting effects on Mediterranean riparian forests, confirming the vulnerability of river ecosystems to clear‐cutting and suggesting the need for more caution in management practices to improve the conservation status of riparian forests.

Reconstructing the historical shoreline evolution of the Northern Bay of Cádiz (SW Spain) from geomorphological and geoarchaeological data

ABSTRACT During the last 3 ka, different human communities occupied the Bay of Cádiz (SW Spain), including Phoenician, Carthaginian, Roman, Medieval and Modern settlements. Traces of such historical occupations have been recognized along the bay from a geoarchaeological point of view. Some of them bear a palaeogeographical interest related to the historical location of the shoreline. At the same time, Holocene sedimentary units and geomorphological elements identified along the bay can be interpreted as evidences of its morphological evolution. The objective of the present paper is to represent all the available data about archaeological sites and geomorphology in the northern Bay of Cádiz, with the aim of combining both sources of data for elaborating a simple proposal of landscape evolution during the last 3 millennia. The base for mapping was multiple, from historical aerial photographs to satellite imagery and a digital terrain model with a maximum resolution of 0.35 m. .

Building an Integrated Database of North-Eastern African Archaeological and Heritage Sites for Mapping Complex Social Landscapes

This dataset contains archaeological and heritage sites of the Marmarica region (NE-Libya/NW-Egypt), ranging from the Late Bronze to the Roman times. It has been developed in the framework of the PERAIA project, which aims to analyse the long-term history and interaction patterns along the harsh environments of north-eastern Africa. The records contain accurate geographic location of sites, including place names, typology, chronology, and metadata of documented remains, along with information regarding the environmental and ecological context. Additionally, the dataset accounts for the specificities of the region&rsquo;s varying environmental conditions and their potential impact on archaeological heritage. All this information associated with each archaeological site was collected from published field data surveys, maps, archaeological reports, and it was subsequently cross-checked with historical aerial photographs and satellite imagery to detect, and to register known and unknown sites within the study area. Regarding the potential reuse of all this data, the dataset is deposited on the project website and linked to Zenodo.

Dynamics throughout a complete surge of Iceberg Glacier on western Axel Heiberg Island, Canadian High Arctic

AbstractThis study provides the first comprehensive reconstruction of the dynamics of Iceberg Glacier, located on western Axel Heiberg Island, and reveals detailed observations of a complete surge for the first time in the Canadian Arctic. Historical aerial photographs, declassified intelligence satellite photographs, optical satellite imagery and synthetic aperture radar data were used to quantify changes in terminus position, ice velocity and glacier thickness since the 1950s. A surge initiated at the terminus in 1981 and terminated in 2003, suggesting a 22-year active phase. High surface velocities, reaching ~2300 m a−1 in 1991, were accompanied by a maximum terminus advance of &gt;7 km and a large transfer of mass down-glacier, causing significant median trunk-wide surface elevation changes attaining &gt;3 ± 1 m a−1. We suggest that the retreat from a pinning point, flotation of the terminus, the removal of sea-ice from the ice front, and an increase in subglacial meltwater availability from relatively high air temperatures in 1981 likely contributed to surge initiation. The ensuing quiescent period has seen a continual decrease in surface flow rates to an average centreline velocity of 11.5 m a−1 in 2020–21, a gradual steepening of the glacier surface and a &gt; 2.5 km terminus retreat.

An Optimized Workflow for Digital Surface Model Series Generation Based on Historical Aerial Images: Testing and Quality Assessment in the Beach-Dune System of Sa Ràpita-Es Trenc (Mallorca, Spain)

We propose an optimized Structure-from-Motion (SfM) Multi-View Stereopsis (MVS) workflow, based on minimizing different errors and inaccuracies of historical aerial photograph series (1945, 1979, 1984, and 2008 surveys), prior to generation of elevation-calibrated historical Digital Surface Models (hDSM) at 1 m resolution. We applied LiDAR techniques on Airborne Laser Scanning (ALS) point clouds (Spanish PNOA LiDAR flights of 2014 and 2019) for comparison and validation purposes. Implementation of these products in multi-temporal analysis requires quality control due to the diversity of sources and technologies involved. To accomplish this, (i) we used the Mean Absolute Error (MAE) between GNSS-Validation Points and the elevations observed by DSM-ALS to evaluate the elevation accuracy of DSM-ALS generated with the LAScatalog processing engine; (ii) optimization of the SfM sparse clouds in the georeferencing step was evaluated by calculating the Root Mean Square Error (RMSE) between the Check Points extracted from DSM-ALS and the predicted elevations per sparse cloud; (iii) the MVS clouds were evaluated by calculating the MAE between ALS-Validation Points and the predicted elevations per MVS cloud; iv) the accuracy of the resulting historical SfM-MVS DSMs were assessed using the MAE between ALS-Validation Points and the observed elevations per historical DSM; and (v) we implemented a calibration method based on a linear correction to reduce the elevation discrepancies between historical DSMs and the DSM-ALS 2019 reference elevations. This optimized workflow can generate high-resolution (1 m pixel size) hDSMs with reasonable accuracy: MAE in z ranges from 0.41 m (2008 DSM) to 5.21 m (1945 DSM). Overall, hDSMs generated using historical images have great potential for geo-environmental processes monitoring in different ecosystems and, in some cases (i.e., sufficient image overlapping and quality), being an acceptable replacement for LiDAR data when it is not available.