scholarly journals Brief Communication: Mapping river ice using drones and structure from motion

2018 ◽  
Vol 12 (2) ◽  
pp. 627-633 ◽  
Author(s):  
Knut Alfredsen ◽  
Christian Haas ◽  
Jeffrey A. Tuhtan ◽  
Peggy Zinke
Keyword(s):  
Structure From Motion ◽  
Low Cost ◽  
Cold Climate ◽  
River Ice ◽  
River Morphology ◽  
Ice Thickness ◽  
Surface Model ◽  
Engineering Data ◽  
Site Access ◽  
Remote Sensing Methods

Abstract. In cold climate regions, the formation and break-up of river ice is important for river morphology, winter water supply, and riparian and instream ecology as well as for hydraulic engineering. Data on river ice is therefore significant, both to understand river ice processes directly and to assess ice effects on other systems. Ice measurement is complicated due to difficult site access, the inherent complexity of ice formations, and the potential danger involved in carrying out on-ice measurements. Remote sensing methods are therefore highly useful, and data from satellite-based sensors and, increasingly, aerial and terrestrial imagery are currently applied. Access to low cost drone systems with quality cameras and structure from motion software opens up a new possibility for mapping complex ice formations. Through this method, a georeferenced surface model can be built and data on ice thickness, spatial distribution, and volume can be extracted without accessing the ice, and with considerably fewer measurement efforts compared to traditional surveying methods. A methodology applied to ice mapping is outlined here, and examples are shown of how to successfully derive quantitative data on ice processes.

scholarly journals Brief communication: Mapping river ice using drones and structure from motion

2017 ◽  
Author(s):  
Knut Alfredsen ◽  
Christian Haas ◽  
Jeffrey A. Tuhtan ◽  
Peggy Zinke
Keyword(s):  
Structure From Motion ◽  
Low Cost ◽  
Cold Climate ◽  
River Ice ◽  
River Morphology ◽  
Ice Thickness ◽  
Potential Danger ◽  
Engineering Data ◽  
Site Access ◽  
Remote Sensing Methods

Abstract. In cold climate regions, the formation and break-up of river ice is important for river morphology, winter water supply, riparian and instream ecology as well as for hydraulic engineering. Data on river ice is therefore significant, both to understand river ice processes directly and to assess ice effects on other systems. Ice measurement is complicated due to difficult site access, the inherent complexity of ice formations and the potential danger involved in carrying out on-ice measurements. Remote sensing methods are therefore highly useful, and satellite imagery, data from satellite-based radars as increasingly aerial and terrestrial imagery are currently applied. Access to low cost drone systems with quality cameras and Structure from Motion software opens up a new possibility for mapping complex ice formations. Through this method, a georeferenced DEM can be built and data on ice thickness, spatial distribution and volume can be extracted without accessing the ice and with considerable less measurement efforts compared to traditional surveying methods. The methodology applied to ice mapping is outlined here, and examples are shown on how to successfully apply the method to derive data on ice processes.

scholarly journals Drone Surveying of Volumetric Ice Growth in a Steep River

2021 ◽  
Vol 2 ◽  
Author(s):  
Einar Rødtang ◽  
Knut Alfredsen ◽  
Ana Juárez
Keyword(s):  
Structure From Motion ◽  
Complex Geometry ◽  
Low Cost ◽  
Single Point ◽  
Ice Cover ◽  
River Ice ◽  
Ice Thickness ◽  
Surface Geometry ◽  
Ice Volume ◽  
Anchor Ice

Representative ice thickness data is essential for accurate hydraulic modelling, assessing the potential for ice induced floods, understanding environmental conditions during winter and estimation of ice-run forces. Steep rivers exhibit complex freeze-up behaviour combining formation of columnar ice with successions of anchor ice dams to build a complete ice cover, resulting in an ice cover with complex geometry. For such ice covers traditional single point measurements are unrepresentative. Gathering sufficiently distributed measurements for representativeness is labour intensive and at times impossible with hard to access ice. Structure from Motion (SfM) software and low-cost drones have enabled river ice mapping without the need to directly access the ice, thereby reducing both the workload and the potential danger in accessing the ice. In this paper we show how drone-based photography can be used to efficiently survey river ice and how these photographic surveys can be processed into digital elevation models (DEMs) using Structure from Motion. We also show how DEMs of the riverbed, riverbanks and ice conditions can be used to deduce ice volume and ice thickness distributions. A QGIS plugin has been implemented to automate these tasks. These techniques are demonstrated with a survey of a stretch of the river Sokna in Trøndelag, Norway. The survey was carried out during the winter 2020–2021 at various stages of freeze-up using a simple quadcopter with camera. The 500 m stretch of river studied was estimated to have an ice volume of up to 8.6 × 103 m3 (This corresponds to an average ice thickness of ∼67 cm) during the full ice cover condition of which up to 7.2 × 103 m3 (This corresponds to an average ice thickness of ∼57 cm) could be anchor ice. Ground Control Points were measured with an RTK-GPS and used to determine that the accuracy of these ice surface geometry measurements lie between 0.03 and 0.09 m. The ice thicknesses estimated through the SfM methods are on average 18 cm thicker than the manual measurements. Primarily due to the SfM methods inability to detect suspended ice covers. This paper highlights the need to develop better ways of estimating the volume of air beneath suspended ice covers.

scholarly journals Mapping of River Terraces with Low-Cost UAS Based Structure-from-Motion Photogrammetry in a Complex Terrain Setting

2019 ◽  
Vol 11 (4) ◽  
pp. 464 ◽  
Author(s):  
Hui Li ◽  
Lin Chen ◽  
Zhaoyang Wang ◽  
Zhongdi Yu
Keyword(s):  
Structure From Motion ◽  
Complex Terrain ◽  
Laser Scanning ◽  
Low Cost ◽  
Unmanned Aerial Systems ◽  
Surface Model ◽  
Simple Method ◽  
River Terraces ◽  
Geomorphic Features ◽  
Topography Data

River terraces are the principal geomorphic features for unraveling tectonics, sea level, and climate conditions during the evolutionary history of a river. The increasing availability of high-resolution topography data generated by low-cost Unmanned Aerial Systems (UAS) and modern photogrammetry offer an opportunity to identify and characterize these features. In this paper, we assessed the capabilities of UAS-based Structure-from-Motion (SfM) photogrammetry, coupled with a river terrace detection algorithm for mapping of river terraces over a 1.9 km2 valley of complex terrain setting, with a focus on the performance of this latest technology over such complex terrains. With the proposed image acquisition approach and SfM photogrammetry, we constructed a 3.8 cm resolution orthomosaic and digital surface model (DSM). The vertical accuracy of DSM was assessed against 196 independent checkpoints measured with a real-time kinematic (RTK) GPS. The results indicated that the root mean square error (RMSE) and mean absolute error (MAE) were 3.1 cm and 2.9 cm, respectively. These encouraging results suggest that this low-cost, logistically simple method can deliver high-quality terrain datasets even in the complex terrain, competitive with those obtained using more expensive laser scanning. A simple algorithm was then employed to detect river terraces from the generated DSM. The results showed that three levels of river terraces and a high-level floodplain were identified. Most of the detected river terraces were confirmed by field observations. Despite the highly erosive nature of fluvial systems, this work obtained good results, allowing fast analysis of fluvial valleys and their comparison. Overall, our results demonstrated that the low-cost UAS-based SfM technique could yield highly accurate ultrahigh-resolution topography data over complex terrain settings, making it particularly suitable for quick and cost-effective mapping of micro to medium-sized geomorphic features under such terrains in remote or poorly accessible areas. Methods discussed in this paper can also be applied to produce highly accurate digital terrain data over large spatial extents for some other places of complex terrains.

scholarly journals A Canadian River Ice Database from the National Hydrometric Program Archives

2020 ◽  
Vol 12 (3) ◽  
pp. 1835-1860 ◽  
Author(s):  
Laurent de Rham ◽  
Yonas Dibike ◽  
Spyros Beltaos ◽  
Daniel Peters ◽  
Barrie Bonsal ◽  
...  
Keyword(s):  
Water Level ◽  
Hydrological Cycle ◽  
Open Water ◽  
Cold Climate ◽  
River Ice ◽  
Ice Thickness ◽  
Original Research ◽  
Data Set ◽  
Spring Break ◽  
Break Up

Abstract. River ice, like open-water conditions, is an integral component of the cold-climate hydrological cycle. The annual succession of river ice formation, growth, decay and clearance can include low flows and ice jams, as well as midwinter and spring break-up events. Reports and associated data of river ice occurrence are often limited to single locations or regional assessments, are season-specific, and use readily available data. Within Canada, the National Hydrometric Program (NHP) operates a network of gauging stations with water level as the primary measured variable to derive discharge. In the late 1990s, the Water Science and Technology Directorate of Environment and Climate Change Canada initiated a long-term effort to compile, archive and extract river-ice-related information from NHP hydrometric records. This data article describes the original research data set produced by this near 20-year effort: the Canadian River Ice Database (CRID). The CRID holds almost 73 000 recorded variables from a subset of 196 NHP stations throughout Canada that were in operation within the period 1894 to 2015. Over 100 000 paper and digital files were reviewed, representing 10 378 station years of active operation. The task of compiling this database involved manual extraction and input of more than 460 000 data entries on water level, discharge, ice thickness, date, time and data quality rating. Guidelines on the data extraction, rating procedure and challenges are provided. At each location, time series of up to 15 variables specific to the occurrence of freeze-up and winter-low events, midwinter break-up, ice thickness, spring break-up, and maximum open-water level were compiled. This database follows up on several earlier efforts to compile information on river ice, which are summarized herein, and expands the scope and detail for use in Canadian river ice research and applications. Following the Government of Canada Open Data initiative, this original river ice data set is available at https://doi.org/10.18164/c21e1852-ba8e-44af-bc13-48eeedfcf2f4 (de Rham et al., 2020).

scholarly journals Demystifying the Differences between Structure-from-Motion Software Packages for Pre-Processing Drone Data

Drones ◽  
2022 ◽  
Vol 6 (1) ◽  
pp. 24
Author(s):  
Taleatha Pell ◽  
Joan Y. Q. Li ◽  
Karen E. Joyce
Keyword(s):  
Structure From Motion ◽  
Software Package ◽  
Low Cost ◽  
Surface Model ◽  
Digital Surface Model ◽  
Output File ◽  
Environmental Assessments ◽  
Processing Times ◽  
Software Packages ◽  
Digital Elevation

With the increased availability of low-cost, off-the-shelf drone platforms, drone data become easy to capture and are now a key component of environmental assessments and monitoring. Once the data are collected, there are many structure-from-motion (SfM) photogrammetry software options available to pre-process the data into digital elevation models (DEMs) and orthomosaics for further environmental analysis. However, not all software packages are created equal, nor are their outputs. Here, we evaluated the workflows and output products of four desktop SfM packages (AgiSoft Metashape, Correlator3D, Pix4Dmapper, WebODM), across five input datasets representing various ecosystems. We considered the processing times, output file characteristics, colour representation of orthomosaics, geographic shift, visual artefacts, and digital surface model (DSM) elevation values. No single software package was determined the “winner” across all metrics, but we hope our results help others demystify the differences between the options, allowing users to make an informed decision about which software and parameters to select for their specific application. Our comparisons highlight some of the challenges that may arise when comparing datasets that have been processed using different parameters and different software packages, thus demonstrating a need to provide metadata associated with processing workflows.

Rapid mapping accuracy assessment using low-cost UAV and open-source Structure from Motion

2020 ◽  
Vol 52 ◽  
pp. 55-61
Author(s):  
Ettore Potente ◽  
Cosimo Cagnazzo ◽  
Alessandro Deodati ◽  
Giuseppe Mastronuzzi
Keyword(s):  
Open Source ◽  
Structure From Motion ◽  
Accuracy Assessment ◽  
Low Cost ◽  
Mapping Accuracy ◽  
Rapid Mapping ◽  
Source Structure

Failure Analysis of Cementless Hip Joint Prosthesis

2013 ◽  
Vol 845 ◽  
pp. 403-407
Author(s):  
Natesan Dhandapani ◽  
A. Gnanavelbabu ◽  
M. Sivasankar
Keyword(s):  
Hip Joint ◽  
Low Cost ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Element Model ◽  
Von Mises Stress ◽  
Surface Model ◽  
Joint Prosthesis ◽  
Replacement Technique ◽  
Von Mises

In this changing global scenario, modification, transplantation, and replacement can be the eternal solution for most of the problems in the medical field. Hence replacement technique finds a very prominent place in medicine as a remedy having closely tied up with biomechanics. One of the most important joints in the human body is the hip joint, the big and complex joint. Many researches were conducted and many are in progress, but most of these works use simplified models with either 2D or 3D approaches. The hip joint is formed by four components like femoral head cortical bone, stem, and neck. In this system we can find orthotropic and isotropic materials working together. The main objective of this research is to develop a three dimensional surface and solid finite element model of the hip joint to predict stresses in its individual components. This model is a geometric non-linear model, which helps us understand its structural mechanical behavior, seeming to suggest with advanced research in the future new hip joint prosthesis, as well as to prove the prosthesis joint interaction before being implanted in the patient. This research explains a complete human hip joint model without cartilaginous tissue, using ANSYS 10.0 Multiphysics Analysis for nine different postures in hip joint using three different materials (CoCr, Ti6Al4V, and UHMWPE) to calculate fatigue life. The result obtained from the analysis of surface model and solid model serve to help in predicting the life cycle, surface characteristics, shear stress in XY plane, stress concentration and areas that are prone to failure. Von Mises stress on the surface of our model facilitates us to equip and design an optimized prosthesis device having unique materials composition , with a highly bio-compatible and durable alloy at a low cost could be produced. In this way, a first important step towards the structural characterization of human hip joint has been developed.

scholarly journals Annual variation characteristics of Eurasian hydrologic elements and their linkage with climate and environment changes during 1951–2015

2019 ◽  
Author(s):  
Jia Qin ◽  
Yongjian Ding ◽  
Tianding Han ◽  
Junhao Li ◽  
Shaoping Wang ◽  
...  
Keyword(s):  
Snow Water Equivalent ◽  
Discharge Pattern ◽  
River Ice ◽  
Ice Thickness ◽  
High Latitudes ◽  
Middle Latitudes ◽  
Variation Characteristics ◽  
Snow Water ◽  
The 1950S ◽  
Monthly Discharge

Abstract. In this paper, the variations of the lowest monthly discharge (LD), mean monthly discharge (MD), and highest monthly discharge value (HD) during 1951–2015, as well as spring snowmelt water and winter river ice change, in eleven major rivers, distributed respectively in the high-latitudes (55° N–70° N), middle latitudes (40° N–55° N), and lower latitudes (30° N–40° N) of Eurasia, were analysed. Energy and water budgets in different watersheds were compared to detect the reasons for Eurasian hydrological changes. We found that the annual LD in most Eurasian rivers was increasing since the 1950s, with rates of (5 %–8 %) per decade. But the increase rate slowed down after the late 1990s in the middle latitudes of Eurasia. Both the MD and HD in the lower latitudes of Eurasia had increasing trends during 1951–2015, while they had little changes in the high and middle latitudes. The river ice thickness and volume have been continuously reducing since the 1950s, as well as the maximum snow water equivalent. And ice period of the Eurasian rivers has shortened about 24 days. The LD trend is mostly dominated by temperature via impacting river ice thickness and extent, while the HD is mostly impacted by snowmelt water and rainfall respectively in different latitudes. Annual MD trend is controlled by evapotranspiration, especially after the late 1990s. After the late 1990s, a warm Arctic-large discharge pattern existed in the lower and high latitudes of Eurasia, but a warm Arctic- few discharge pattern in the middle latitudes (except the winter).

scholarly journals UNDERWATER PHOTOGRAMMETRY DIGITAL SURFACE MODEL (DSM) OF THE SUBMERGED SITE OF THE ANCIENT LIGHTHOUSE NEAR QAITBAY FORT IN ALEXANDRIA, EGYPT

2019 ◽  
Vol XLII-2/W10 ◽  
pp. 1-8 ◽  
Author(s):  
M. Abdelaziz ◽  
M. Elsayed
Keyword(s):  
3D Model ◽  
Low Cost ◽  
Data Gathering ◽  
Archaeological Site ◽  
3D Models ◽  
Surface Model ◽  
Digital Surface Model ◽  
Architectural Elements ◽  
3D Photogrammetry ◽  
First Time

<p><strong>Abstract.</strong> Underwater photogrammetry in archaeology in Egypt is a completely new experience applied for the first time on the submerged archaeological site of the lighthouse of Alexandria situated on the eastern extremity of the ancient island of Pharos at the foot of Qaitbay Fort at a depth of 2 to 9 metres. In 2009/2010, the CEAlex launched a 3D photogrammetry data-gathering programme for the virtual reassembly of broken artefacts. In 2013 and the beginning of 2014, with the support of the Honor Frost Foundation, methods were developed and refined to acquire manual photographic data of the entire underwater site of Qaitbay using a DSLR camera, simple and low cost materials to obtain a digital surface model (DSM) of the submerged site of the lighthouse, and also to create 3D models of the objects themselves, such as statues, bases of statues and architectural elements. In this paper we present the methodology used for underwater data acquisition, data processing and modelling in order to generate a DSM of the submerged site of Alexandria’s ancient lighthouse. Until 2016, only about 7200&amp;thinsp;m<sup>2</sup> of the submerged site, which exceeds more than 13000&amp;thinsp;m<sup>2</sup>, was covered. One of our main objectives in this project is to georeference the site since this would allow for a very precise 3D model and for correcting the orientation of the site as regards the real-world space.</p>

Estimating the thickness of ridged sea ice from ship observations in the Ross Sea

2003 ◽  
Vol 15 (1) ◽  
pp. 47-54 ◽  
Author(s):  
TINA TIN ◽  
MARTIN O. JEFFRIES ◽  
MIKKO LENSU ◽  
JUKKA TUHKURI
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Low Cost ◽  
Thickness Distribution ◽  
Ice Thickness ◽  
Equivalent Thickness ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Using Data ◽  
Original Formula

Ship-based observations of sea ice thickness using the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol provide information on ice thickness distribution at relatively low cost. This protocol uses a simple formula to calculate the mass of ice in ridges based on surface observations. We present two new formulae and compare these with results from the “Original” formula using data obtained in the Ross Sea in autumn and winter. The new “r-star” formula uses a more realistic ratio of sail and keel areas to transform dimensions of sails to estimates of mean keel areas. As a result, estimates of “equivalent thickness” (i.e. mean thickness of ice in ridged areas) increased by over 200%. The new “Probability” formula goes one step further, by incorporating the probability that a sail is associated with a keel underwater, and the probability that keels may be found under level surfaces. This resulted in estimates of equivalent thickness comparable with the Original formula. Estimates of equivalent thickness at one or two degree latitude resolution are sufficiently accurate for validating sea ice models. Although ridges are small features in the Ross Sea, we have shown that they constitute a significant fraction of the total ice mass.

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