scholarly journals Marine Coastline Polygonal Ridges and Surface Roughness Development on a Salt-Crusted Playa: Recognition by Structure-from-Motion Photogrammetry

2019 ◽  
Vol 7 (3) ◽  
pp. 76
Author(s):  
Yuyang Geng ◽  
Yun Shao ◽  
Huaze Gong ◽  
Brian Brisco ◽  
Yang Zhi ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Structure From Motion ◽  
Salt Lake ◽  
Dust Emission ◽  
Field Work ◽  
Surface Evolution ◽  
Digital Elevation ◽  
Lop Nur ◽  
Salt Crust ◽  
Elevation Model

Salt crust is a normal landform in drying-out salt lake basins or marine regression coastlines, but the surface evolution processes over a decadal or even centenary period are not well understood due to poor data records. Microrelief characteristics control erodibility and erosivity, which will significantly influence wind erosion and dust emission. It is essential to classify the microrelief pattern of salt crust for mapping its spatial distribution and evaluating the environmental process. A desiccated inland tail-end lake would be an example of the coastline surface evolution after regression and represent a good case study of salt crust because of the fewer exogenic process interruptions. For this paper, field work was performed in the Lop Nur playa in China, about 90° E, 40° N, which used to be a salt lake half a century ago. Ground-based photos of the salt crust were acquired and imported into structure-from-motion (SfM) software to produce a fine centimeter-scale digital elevation model (DEM). Two indexes were introduced and extracted from the digital elevation model to classify various types of salt crust: roughness was calculated to evaluate the magnitude and the gray-level co-occurrence matrix (GLCM) score was derived to describe the structure pattern of the salt crust. Moreover, in this paper, sedimentary features during different parts of a playa evaporation cycle are reviewed and peculiar kinds of salt crust found on Lop Nur are further discussed.

scholarly journals ОПЫТ ДОКУМЕНТИРОВАНИЯ МЕГАЛИТИЧЕСКИХ СТЕЛ С ГЛУБОКИМ РЕЛЬЕФОМ (ЗАПАДНОЕ ЗАБАЙКАЛЬЕ)

2019 ◽  
Author(s):  
В.В. Казаков ◽  
В.С. Ковалев ◽  
А.И. Симухин ◽  
П.Е. Марнуев ◽  
Д.В. Намсараев
Keyword(s):  
Edge Detection ◽  
Digital Elevation Model ◽  
Structure From Motion ◽  
Canny Edge Detection ◽  
Digital Elevation ◽  
Canny Edge ◽  
Elevation Model

На протяжении последних нескольких лет в археологии активно исследуются возможности цифровой фиксации древних рисунков и надписей на основе их рельефа. С недавнего времени заметен активный научный интерес в направлении автоматизации процесса фиксации изображений на стелах. Авторами апробирована методика программной автоматизации выполнения прорисовок рельефных изображений на примере единственного сохранившегося классического оленного камня монголо-забайкальского типа. Памятник находится на территории Тамчинского дацана в Селенгинском районе Бурятии и используется в контексте буддийской ритуальной практики. Методика заключается в последовательном выполнении ряда операций. Вначале требуется получить трехмерную модель объекта с помощью SfMфотограмметрии на основе серии фотографий, выполненных в поле. SfM (Structure-from-Motion) фотограмметрия метод получения трехмерной модели на основе набора перекрывающихся фотографий с разного положения фотокамеры относительно объекта. Далее, по имеющейся трехмерной модели необходимо сгенерировать ортофотографии и построить DEM-модели плоскостей с рисунками. DEM (Digital Elevation Model) цифровая модель рельефа, т.е. карта высот ландшафта. Такие модели широко используются в топографии. В данном случае оказалось, что они могут быть эффективно использованы и для работы с объектами совершенно другого рода наскальными рисунками. Третьим шагом необходимо применить к DEM-моделям плоскостей с рисунками топографический фильтр Positive Openness, разработанного для геоморфологических исследований выделения на поверхности рельефа пиков, впадин, гребней, возвышенностей и т.п. На четвертом этапе к полученным растровым изображениям с выделенным рельефом применяется графический фильтр Canny Edge Detection. Этот фильтр используется для построения граней деталей изображения на основе анализа резких изменений уровней серого. На заключительном этапе производится ручная черно-белая доработка получившегося изображения в графическом редакторе. Для окончательной прорисовки специалисту требуется дорисовать незаконченные границы рисунков, а лишние грани удалить. После этого замкнутые фигуры заполняются сплошной черной заливкой. Результат такой прорисовки сравним по качеству с прорисовками, выполненными традиционными методами вручную, но, в отличие от них, не инвазивен и лишен геометрических искажений. Преимущество апробированных цифровых методик по отношению к другим способам фиксации изображений (микалентное копирование, прорисовка на прозрачную пленку, фотофиксация) выражено в более точной передаче формы самой стелы, возможности анализа техники нанесения изображений с установлением материала и формы использованных орудий, отсутствии искажений размеров. Использование трехмерного метода фиксации изображений на стелах позволяет выявить и сохранить больше научной информации об объекте. Фотограмметрия является высокоточным, не инвазивным и быстрым методом документирования археологических объектов, а полученные 3D-модели могут быть размещены в открытом доступе в сети Интернет.

scholarly journals A New Beach Topography-Based Method for Shoreline Identification

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3110
Author(s):  
Marco Luppichini ◽  
Monica Bini ◽  
Marco Paterni ◽  
Andrea Berton ◽  
Silvia Merlino
Keyword(s):  
High Resolution ◽  
Digital Elevation Model ◽  
Structure From Motion ◽  
Sea Water ◽  
Beach Profile ◽  
Digital Elevation ◽  
Profile Changes ◽  
Elevation Model ◽  
Definition Of ◽  
Reflecting Surfaces

The definition of shoreline is not the same for all contexts, and it is often a subjective matter. Various methods exist that are based on the use of different instruments that can determine and highlight a shoreline. In recent years, numerous studies have employed photogrammetric methods, based on different colours, to map the boundary between water and land. These works use images acquired by satellites, drones, or cameras, and differ mainly in terms of resolution. Such methods can identify a shoreline by means of automatic, semi-automatic, or manual procedures. The aim of this work is to find and promote a new and valid beach topography-based algorithm, able to identify the shoreline. We apply the Structure from Motion (SfM) techniques to reconstruct a high-resolution Digital Elevation Model by means of a drone for image acquisition. The algorithm is based on the variation of the topographic beach profile caused by the transition from water to sand. The SfM technique is not efficient when applied to reflecting surfaces like sea water resulting in a very irregular and unnatural profile over the sea. Taking advantage of this fact, the algorithm searches for the point in the space where a beach profile changes from irregular to regular, causing a transition from water to land. The algorithm is promoted by the release of a QGIS v3.x plugin, which allows the easy application and extraction of other shorelines.

scholarly journals Remnant surfaces in the Tárkány Basin

2020 ◽  
Vol 14 (2) ◽  
pp. 20-30
Author(s):  
Péter Pecsmány
Keyword(s):  
20Th Century ◽  
Digital Elevation Model ◽  
Geological Mapping ◽  
Surface Evolution ◽  
Field Surveys ◽  
Gis Techniques ◽  
Geological Maps ◽  
Digital Elevation ◽  
Elevation Model ◽  
Made In

The terraces of the Tárkány Basin, located in the SW part of the Bükk Mountains are known since the beginning of the 20th century. Based on field surveys, six morphological levels were delineated and described in 1936. During the later geological mapping surveys, three gravel terraces had been mapped in the basin. Since then, no comprehensive morphological mapping has been made in the Tárkány Basin. Our study aimed to validate the results of these early studies using a digital elevation model. We delineated the remnant surfaces of the basin by morphometric and GIS techniques. Then, based on field surveys and former geological maps; we characterised these remnant surfaces, and their area was measured as well. The results of this study contribute to a better understanding of the surface evolution of the basin and its surroundings.

STUDY OF THE LANDSLIDE MORPHOLOGY BASED ON GNSS DATA AND AIRBORNE SOUNDING (ON THE EXAMPLE OF A SECTION OF THE PROTVA RIVER VALLEY)

2018 ◽  
Vol 12 (5-6) ◽  
pp. 50-57 ◽  
Author(s):  
I. S. Voskresensky ◽  
A. A. Suchilin ◽  
L. A. Ushakova ◽  
V. M. Shaforostov ◽  
A. L. Entin ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Geodetic Network ◽  
Aerial Survey ◽  
River Valley ◽  
Ease Of Use ◽  
Digital Elevation ◽  
Loose Deposits ◽  
Positioning Method ◽  
Landslide Body ◽  
Elevation Model

To use unmanned aerial vehicles (UAVs) for obtaining digital elevation models (DEM) and digital terrain models (DTM) is currently actively practiced in scientific and practical purposes. This technology has many advantages: efficiency, ease of use, and the possibility of application on relatively small area. This allows us to perform qualitative and quantitative studies of the progress of dangerous relief-forming processes and to assess their consequences quickly. In this paper, we describe the process of obtaining a digital elevation model (DEM) of the relief of the slope located on the bank of the Protva River (Satino training site of the Faculty of Geography, Lomonosov Moscow State University). To obtain the digital elevation model, we created a temporary geodetic network. The coordinates of the points were measured by the satellite positioning method using a highprecision mobile complex. The aerial survey was carried out using an unmanned aerial vehicle from a low altitude (about 40–45 m). The processing of survey materials was performed via automatic photogrammetry (Structure-from-Motion method), and the digital elevation model of the landslide surface on the Protva River valley section was created. Remote sensing was supplemented by studying archival materials of aerial photography, as well as field survey conducted immediately after the landslide. The total amount of research results made it possible to establish the causes and character of the landslide process on the study site. According to the geomorphological conditions of formation, the landslide refers to a variety of landslideslides, which are formed when water is saturated with loose deposits. The landslide body was formed with the "collapse" of the blocks of turf and deluvial loams and their "destruction" as they shifted and accumulated at the foot of the slope.

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