Aerial image capture has become very common within the geosciences due to the increasing affordability of low payload (<20 kg) Unmanned Aerial Vehicles (UAVs) for consumer markets. Their application to surveying has subsequently led to many studies being undertaken using UAV imagery and derived products as primary data sources. However, image quality and the principles of image capture are seldom given rigorous discussion. In this contribution we firstly revisit the underpinning concepts behind image capture, from which the requirements for acquiring sharp, well exposed and suitable image data are derived. Secondly, the platform, camera, lens and imaging settings relevant to image quality planning are discussed, with worked examples to guide users through the process of considering the factors required for capturing high quality imagery for geoscience investigations.
Given a target feature size and ground sample distance based on mission objectives, flight height and velocity should be calculated to ensure motion blur is kept to a minimum. We recommend using a camera with as big a sensor as is permissible for the aerial platform being used (to maximise sensor sensitivity), effective focal lengths of 24 - 35 mm (to minimize errors due to lens distortion) and optimising ISO (to ensure shutter speed is fast enough to minimise motion blur). Finally, we give recommendations for the reporting of results by researchers in order to help improve the confidence in, and reusability of, surveys through: providing open access imagery where possible, presenting example images and excerpts, and detailing appropriate metadata to rigorously describe the image capture process.
As you will see with this Editorial, it has been a year ofintense activity at the Journal of Maps (JoM). The mostimportant announcement is the move of JoM back toan Open Access (OA) publishing model which waseffective from 1st September 2016.
With the boom in the use of consumer-grade cameras on unmanned aerial vehicles (UAVs) for surveying and photogrammetric applications, this article seeks to review a range of different cameras and their critical attributes. Firstly, it establishes the most important considerations when selecting a camera for surveying. Secondly, the authors make a number of recommendations at various price points.
Elsevier’s Modern Cartography Series, edited by Professor DR Fraser Taylor, is a long-running occasional series that currently comprises seven volumes, the first published in 1991. With a hia-tus since 2006, Elsevier has injected some new vigour with a title planned for 2017 and this volume, Reflexive Cartography, pub-lished in 2015.
Sediments beneath modern ice sheets exert a key control on their flow, but are largely inaccessible except through geophysics or boreholes. In contrast, palaeo-ice sheet beds are accessible, and typically characterised by numerous bedforms. However, the interaction between bedforms and ice flow is poorly constrained and it is not clear how bedform sizes might reflect ice flow conditions. To better understand this link we present a first exploration of a variety of statistical models to explain the size distribution of some common subglacial bedforms (i.e., drumlins, ribbed moraine, MSGL). By considering a range of models, constructed to reflect key aspects of the physical processes, it is possible to infer that the size distributions are most effectively explained when the dynamics of ice-water-sediment interaction associated with bedform growth is fundamentally random. A ’stochastic instability’ (SI) model, which integrates random bedform growth and shrinking through time with exponential growth, is preferred and is consistent with other observations of palaeo-bedforms and geophysical surveys of active ice sheets. Furthermore, we give a proof-of-concept demonstration that our statistical approach can bridge the gap between geomorphological observations and physical models, directly linking measurable size-frequency parameters to properties of ice sheet flow (e.g., ice velocity). Moreover, statistically developing existing models as proposed allows quantitative predictions to be made about sizes, making the models testable; a first illustration of this is given for a hypothesised repeat geophysical survey of bedforms under active ice. Thus, we further demonstrate the potential of size-frequency distributions of subglacial bedforms to assist the elucidation of subglacial processes and better constrain ice sheet models.
The Map Room highlighted the Journal of Maps Best Maps today in this blog post. Our Best Maps are freely available, but since being published in partnership with Taylor and Francis we have become subscription based which means everything up to 2012 is open access.
FYI, and I’ve written about this in my editorials on several occasions, publishing a journal is not a “no-cost” opration. Increasingly, in order to meet the expected standards of readers, authors, funders and the general public, there are a number of quality requirements. So, in short, someone, somewhere, at somepoint, has to pay for publication. That can be the reader (subscription), the author (open access) or some hybrid (cross-subsidy!). It’s something we always keep under review at the Journal of Maps - unfortunately no model suits everyone.
What is a map? A seemingly innocuous question that is deftly handled by the International Cartographic Association (ICA, 2015) as
“a symbolised representation of geographical reality, representing selected features or characteristics, resulting from the creative effort of its author’s execution of choices, and is designed for use when spatial relationships are of primary relevance.”"
Datasets containing large numbers (>10,000) of glacial lineaments are increasingly being mapped from remotely sensed data in order to develop a palaeo-glacial reconstruction or “inversion”. The palimpsest landscape presents a complex record of past ice flow and deconstructing this information into a logical history is an involved task. One stage in this process requires the identification of sets of genetically linked lineaments that can form the basis of a reconstruction.
This paper presents a semi-automated algorithm, CLustre, for lineament clustering that uses a locally adaptive, region growing, methodology. After outlining the algorithm, it is tested on synthetic datasets that simulate parallel and orthogonal cross-cutting lineaments, encompassing 1,500 separate classifications. Results show robust classification in most scenarios, although parallel overlap of lineaments can cause false positive classification unless there are differences in lineament length. Case studies for Dubawnt Lake and Victoria Island, Canada, are presented and compared to existing datasets. For Dubawnt Lake 9 out of 14 classifications directly match incorporating 89% of lineaments. For Victoria Island 57 out of 58 classifications directly match incorporating 95% of lineaments. Differences are related to small numbers of unclassified lineaments and parallel cross-cutting lineaments that are of a similar length.
CLustre enables the automated, repeatable, assignment of lineaments to flow sets using defined user criteria. This is important as qualitative visual interpretation may introduce bias, potentially weakening the testability of palaeo-glacial reconstructions. In addition, once classified, summary statistics of lineament clusters can be calculated and subsequently used during the reconstruction process.
O’Connor, J. and Smith, M.J. (2015)
Surveys using UAVs and photogrammetry are becoming ubiquitous. It is in the community’s best interests to remember the fundamentals of image capture. James O’Connor and Mike J Smith of the School of Geography, Geology and the Environment, Kingston University review the main considerations for image capture when undertaking an aerial survey using consumer grade cameras and make recommendations for acquiring the best imagery.
This paper considers legacy data and data rescue within the context of geomorphology. Data rescue may be necessary dependent upon the storage medium (is it physically accessible) and the data format (e.g. digital file type); where either of these is not functional, intervention will be required in order to retrieve the stored data. Within geomorphological research, there are three scenarios that may utilize legacy data: to reinvestigate phenomena, to access information about a landform/process that no longer exists, and to investigate temporal change. Here, we present three case studies with discussion that illustrate these scenarios: striae records of Ireland were used to produce a palaeoglacial reconstruction, geomorphological mapping was used to compile a map of glacial landforms, and aerial photographs were used to analyze temporal change in river channel form and catchment land cover.