scholarly journals How does grid-resolution modulate the topographic expression of geomorphic processes?

2016 ◽  
Author(s):  
Stuart W. D. Grieve ◽  
Simon M. Mudd ◽  
David T. Milodowski ◽  
Fiona J. Clubb ◽  
David J. Furbish
Keyword(s):  
High Resolution ◽  
Point Clouds ◽  
The United States ◽  
Careful Consideration ◽  
Grid Resolution ◽  
Topographic Analysis ◽  
Topographic Data ◽  
Digital Elevation ◽  
D Values ◽  
Resolution Data

Abstract. In many locations, our ability to study the processes which shape the Earth are greatly enhanced through the use of high resolution digital topographic data. However, although the availability of such datasets has markedly increased in recent years, many locations of significant geomorphic interest still do not have high resolution topographic data available. Here, we aim to constrain how well we can understand surface processes through topographic analysis performed on lower resolution data. We generate digital elevation models from point clouds at a range of grid sizes from 1 to 30 m, which covers the range of widely used data resolutions available globally, at three locations in the United States. Using this data, the relationship between curvature and grid resolution is explored, alongside the estimation of the hillslope sediment transport coefficient (D, in m2 yr−1) for each landscape. Curvature, and consequently D, values are shown to be generally insensitive to grid resolution, particularly in landscapes with broad hilltops and valleys. Curvature distributions, however, become increasingly condensed around the mean, and theoretical considerations suggest caution should be used when extracting curvature from landscapes with sharp ridges. Two methods of extracting channels from topographic data are tested. A geometric method of channel extraction that finds channels by detecting threshold values of planform curvature is shown to perform well at resolutions up to 30 m in all three landscapes. The landscape parameters of hillslope length and relief are both successfully extracted at the same range of resolutions. These parameters can be used to detect landscape transience and our results suggest that such work need not be confined to high resolution topographic data. A synthesis of the results presented in this work indicate that although high resolution (e.g., 1 m) topographic data does yield exciting possibilities for geomorphic research, many key parameters can be understood in lower resolution data, given careful consideration of how analyses are performed.

scholarly journals How does grid-resolution modulate the topographic expression of geomorphic processes?

2016 ◽  
Vol 4 (3) ◽  
pp. 627-653 ◽  
Author(s):  
Stuart W. D. Grieve ◽  
Simon M. Mudd ◽  
David T. Milodowski ◽  
Fiona J. Clubb ◽  
David J. Furbish
Keyword(s):  
High Resolution ◽  
Point Clouds ◽  
The United States ◽  
Careful Consideration ◽  
Grid Resolution ◽  
Topographic Analysis ◽  
Topographic Data ◽  
Digital Elevation ◽  
D Values ◽  
Resolution Data

Abstract. In many locations, our ability to study the processes which shape the Earth are greatly enhanced through the use of high-resolution digital topographic data. However, although the availability of such datasets has markedly increased in recent years, many locations of significant geomorphic interest still do not have high-resolution topographic data available. Here, we aim to constrain how well we can understand surface processes through topographic analysis performed on lower-resolution data. We generate digital elevation models from point clouds at a range of grid resolutions from 1 to 30 m, which covers the range of widely used data resolutions available globally, at three locations in the United States. Using these data, the relationship between curvature and grid resolution is explored, alongside the estimation of the hillslope sediment transport coefficient (D, in m2 yr−1) for each landscape. Curvature, and consequently D, values are shown to be generally insensitive to grid resolution, particularly in landscapes with broad hilltops and valleys. Curvature distributions, however, become increasingly condensed around the mean, and theoretical considerations suggest caution should be used when extracting curvature from landscapes with sharp ridges. The sensitivity of curvature and topographic gradient to grid resolution are also explored through analysis of one-dimensional approximations of curvature and gradient, providing a theoretical basis for the results generated using two-dimensional topographic data. Two methods of extracting channels from topographic data are tested. A geometric method of channel extraction that finds channels by detecting threshold values of planform curvature is shown to perform well at resolutions up to 30 m in all three landscapes. The landscape parameters of hillslope length and relief are both successfully extracted at the same range of resolutions. These parameters can be used to detect landscape transience and our results suggest that such work need not be confined to high-resolution topographic data. A synthesis of the results presented in this work indicates that although high-resolution (e.g., 1 m) topographic data do yield exciting possibilities for geomorphic research, many key parameters can be understood in lower-resolution data, given careful consideration of how analyses are performed.

scholarly journals A method based on structure-from-motion photogrammetry to generate sub-millimetre-resolution digital elevation models for investigating rock breakdown features

2019 ◽  
Vol 7 (1) ◽  
pp. 45-66 ◽  
Author(s):  
Ankit Kumar Verma ◽  
Mary Carol Bourke
Keyword(s):  
High Resolution ◽  
Structure From Motion ◽  
Low Cost ◽  
Digital Elevation Models ◽  
Point Clouds ◽  
Experimental Conditions ◽  
Weathered Rock ◽  
Topographic Data ◽  
Digital Elevation ◽  
Dense Point

Abstract. We have generated sub-millimetre-resolution DEMs of weathered rock surfaces using SfM photogrammetry techniques. We apply a close-range method based on structure-from-motion (SfM) photogrammetry in the field and use it to generate high-resolution topographic data for weathered boulders and bedrock. The method was pilot tested on extensively weathered Triassic Moenkopi sandstone outcrops near Meteor Crater in Arizona. Images were taken in the field using a consumer-grade DSLR camera and were processed in commercially available software to build dense point clouds. The point clouds were registered to a local 3-D coordinate system (x, y, z), which was developed using a specially designed triangle-coded control target and then exported as digital elevation models (DEMs). The accuracy of the DEMs was validated under controlled experimental conditions. A number of checkpoints were used to calculate errors. We also evaluated the effects of image and camera parameters on the accuracy of our DEMs. We report a horizontal error of 0.5 mm and vertical error of 0.3 mm in our experiments. Our approach provides a low-cost method for obtaining very high-resolution topographic data on weathered rock surfaces (area < 10 m2). The results from our case study confirm the efficacy of the method at this scale and show that the data acquisition equipment is sufficiently robust and portable. This is particularly important for field conditions in remote locations or steep terrain where portable and efficient methods are required.

scholarly journals A Structure from Motion photogrammetry-based method to generate sub-millimetre resolution Digital Elevation Models for investigating rock breakdown features

2018 ◽  
Author(s):  
Ankit K. Verma ◽  
Mary C. Bourke
Keyword(s):  
High Resolution ◽  
Structure From Motion ◽  
Low Cost ◽  
Digital Elevation Models ◽  
Point Clouds ◽  
Experimental Conditions ◽  
Weathered Rock ◽  
Topographic Data ◽  
Digital Elevation ◽  
Dense Point

Abstract. We have generated sub-millimetre resolution DEMs of weathered rock surfaces using SfM photogrammetry techniques. We apply a close-range Structure from Motion (SfM) photogrammetry-based method in the field and use it to generate high-resolution topographic data for weathered boulders and bedrock. The method was pilot tested on extensively weathered Triassic Moenkopi Sandstone outcrops near Meteor Crater in Arizona. Images were taken in the field using a consumer grade DSLR camera and were processed in commercially available software Agisoft Photoscan to build dense point cloud. Dense point clouds were registered to a local 3D coordinate system (x, y, z) which was developed using a specially designed triangle coded control target and then exported as Digital Elevation Models (DEMs). The accuracy of the DEMs was validated under controlled experimental conditions. A number of checkpoints were used to calculate errors. We also evaluated the effects of image and camera parameters on the accuracy of our DEMs. We report a horizontal error of 0.5 mm and vertical error of 0.3 mm in our experiments. Our approach provides a low-cost method, for obtaining very high-resolution topographic data on weathered rock surfaces (area

High-Resolution Digital Elevation and Bathymetry Model for Tsunami Run-Up and Inundation Simulation in Penang

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941001
Author(s):  
Su Yean Teh ◽  
Hock Lye Koh ◽  
Yong Hui Lim
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Sea Level ◽  
Interpolation Method ◽  
Topographic Maps ◽  
Seamless Integration ◽  
Topographic Data ◽  
Digital Elevation ◽  
Run Up ◽  
Tsunami Run Up

Many beaches in Penang island were severely inundated by the 26 December 2004 Indian Ocean mega tsunami with 57 deaths recorded. It is anticipated that the next big tsunami will cause even more damages to beaches in Penang. Hence, developing community resilience against the risks of the next tsunami is essential. Resilience entails many interlinked components, beginning with a good understanding of the inundation scenarios critical to community evacuation and resilience preparation. Inundation scenarios are developed from tsunami simulations involving all three phases of tsunami generation, propagation and run-up. Accurate and high-resolution bathymetric–topographic maps are essential for simulations of tsunami wave inundation along beaches. Bathymetric maps contain information on the depths of landforms below sea level while topographic maps reveal the elevation of landforms above sea level. Bathymetric and topographic datasets for Malaysia are, however, currently not integrated and are available separately and in different formats, not suitable for inundation simulations. Bathymetric data are controlled by the National Hydrographic Centre (NHC) of the Royal Malaysian Navy while topographic data are serviced by the Department of Survey and Mapping Malaysia (JUPEM). It is highly desirable to have seamless integration of high-resolution bathymetric and topographic data for tsunami simulations and for other scientific studies. In this paper, we develop a robust method for integrating the NHC bathymetric and JUPEM topographic data into a regularly-spaced grid system essential for tsunami simulation. A primary objective of this paper is to develop the best Digital Elevation and Bathymetry Model (DEBM) for Penang based upon the most suitable and accurate interpolation method for integrating bathymetric and topographic data with minimal interpolation errors. We analyze four commonly used interpolation methods for generating gridded topographic and bathymetric surfaces, namely (i) Kriging, (ii) Multiquadric (MQ), (iii) Thin Plate Spline (TPS) and (iv) Inverse Distance to Power (IDP). The study illustrated that the Kriging interpolation method produces an integrated bathymetric and topographic surface that best approximates the admiralty nautical chart of Penang essential for tsunami run-up and inundation simulations. Tsunami inundation scenarios critical to risk analysis and mitigation could then be developed using this DEBM for various earthquake scenarios, as presented in this paper for the 2004 Indian Ocean Tsunami.

scholarly journals Geomorpho90m - Global high-resolution geomorphometry layers: empirical evaluation and accuracy assessment

2019 ◽  
Author(s):  
Giuseppe Amatulli ◽  
Daniel McInerney ◽  
Tushar Sethi ◽  
Peter Strobl ◽  
Sami Domisch
Keyword(s):  
High Resolution ◽  
Accuracy Assessment ◽  
Empirical Evaluation ◽  
Shuttle Radar Topography Mission ◽  
The United States ◽  
Rate Of Change ◽  
Environmental Models ◽  
Digital Elevation ◽  
The Difference ◽  
Elevation Model

Topographical relief is composed of the vertical and horizontal variations of the Earth's terrain and drives processes in geography, climatology, hydrology, and ecology. Its assessment and characterisation is fundamental for various types of modelling and simulation analyses. In this regard, the Multi-Error-Removed Improved Terrain (MERIT) Digital Elevation Model (DEM) is the best global, high-resolution DEM currently available at a 3 arc-seconds (90 m) resolution. This is an improved product as multiple error components have been corrected from the underlying Shuttle Radar Topography Mission (SRTM3) and ALOS World 3D - 30 m (AW3D30) DEMs. To depict topographical variations worldwide, we developed the Geomorpho90m dataset comprising of different geomorphometry features derived from the MERIT-DEM. The fully standardised geomorphometry variables consist of layers that describe (i) the rate of change using the first and second order derivatives, (ii) the ruggedness, and (iii) the geomorphology landform. To assess how remaining artefacts in the MERIT-DEM could affect the derived topographic variables, we compared our results with the same variables generated using the 3D Elevation Program (3DEP) DEM, which is the highest quality DEM for the United States of America. We compared the two data sources by calculating the first order derivative (i.e., the rate of change through space measured in degrees) of the difference between a MERIT-derived vs. a 3DEP-derived topographic variable. All newly-created topographic variables are readily available at resolutions of 3 and 7.5 arc-seconds under the WGS84 geographic system, and at a spatial resolution of 100 m under the Equi7 projection. The newly-developed Geomorpho90m dataset provides a globally standardised dataset for environmental models and analyses in the field of geography, geology, hydrology, ecology and biogeography.

scholarly journals Fusion of high resolution remote sensing images and terrestrial laser scanning for improved biomass estimation of maize

2014 ◽  
Vol XL-7 ◽  
pp. 101-108 ◽  
Author(s):  
C. Hütt ◽  
H. Schiedung ◽  
N. Tilly ◽  
G. Bareth
Keyword(s):  
High Resolution ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Terrestrial Laser Scanning ◽  
Point Clouds ◽  
Satellite System ◽  
Biomass Estimation ◽  
Digital Elevation ◽  
Elevation Model ◽  
In The Beginning

In this study, images from the satellite system WorldView-2 in combination with terrestrial laser scanning (TLS) over a maize field in Germany are investigated. Simultaneously to the measurements a biomass field campaigns was carried out. From the point clouds of the terrestrial laser scanning campaigns crop surface models (CSM) from each scanning date were calculate to model plant growth over time. These results were resampled to match the spatial resolution of the WorldView-2 images, which had to orthorectified using a high resolution digital elevation model and atmosphere corrected using the ATCOR Software package. A high direct correlation of the NDVI calculated from the WorldView-2 sensor and the dry biomass was found in the beginning of June. At the same date, the heights from laser scanning can also explain a certain amount of the biomass variation (<i>r</i><sup>2</sup> = 0.6). By combining the NDVI from WorldView-2 and the height from the laser scanner with a linear model, the R2 reaches higher values of 0.86. To further understand the relationship between CSM derived crop heights and reflection indices, a comparison on a pixel basis was performed. Interestingly, the correlation of the NDVI and the crop height is rather low at the beginning of June (<i>r</i><sup>2</sup> = 0,4, <i>n</i> = 1857) and increases significantly (<i>R</i><sup>2</sup> = 0,79, <i>N</i> = 1857) at a later stage.

scholarly journals Elaborating more accurate high-resolution DEMs using SfM workflow

2018 ◽  
Author(s):  
Alvaro Gomez-Gutierrez ◽  
Trent Biggs ◽  
Napoleon Gudino-Elizondo ◽  
Paz Errea Abad ◽  
Esteban Alonso-González ◽  
...  
Keyword(s):  
High Resolution ◽  
Laser Scanner ◽  
Point Clouds ◽  
Geographical Information ◽  
Aerial Surveys ◽  
Viewshed Analysis ◽  
Digital Elevation ◽  
Ground Point ◽  
Close Range ◽  
Ground Distance

Structure-from-Motion (SfM) photogrammetry is one of the most common approaches used to elaborate high-resolution Digital Elevation Models (DEMs) nowadays. Factors that influence the final error associated to the derived DEM are: camera-to-ground distance, camera-sensor system parameters, image network geometry, matching performance, terrain type, lighting conditions and referencing methods. Here, a strategy focused on minimizing the occlusion produced by topography and determine optimal camera locations for image acquisition is presented. This methodology is based on using a viewshed analysis implemented in a Geographical Information System (GIS) to identify the best images for the SfM workflow of a specific survey-site. The suitability of the workflow presented against conventional acquisition strategies was tested using three different datasets (one terrestrial and two aerial) and analyzing differences between SfM-derived DEM produced using: 1) a dataset acquired following conventional overlap requirements (i.e. one image every 5-10º around the target for terrestrial close-range oblique SfM and 70-60% frontal and side overlap for aerial surveys), 2) a dataset overloaded with images (i.e. one image every 3-4º around the target and >95-95% frontal and side overlap for aerial surveys), and 3) images selected using the viewshed analysis. The resulting DEMs were tested against Terrestrial Laser Scanner-derived (TLS) DEMs. SfM results showed denser point clouds for the datasets elaborated using the viewshed analysis. Differences were particularly important for the terrestrial case indicating a stronger line-of-sight effect on the ground. Point cloud density absolute differences and no-data zones in the datasets produced using the conventional strategies resulted in larger Mean Absolute Errors (MAE) in the DEMs. DEMs produced using the viewshed criteria showed lower MAEs than the conventional dataset and similar to the dataset overloaded of images. Additionally, the processing time of the datasets that used viewshed criteria was much shorter than the datasets overloaded of images.

scholarly journals Fusion of Multi-Sensor-Derived Heights and OSM-Derived Building Footprints for Urban 3D Reconstruction

2019 ◽  
Vol 8 (4) ◽  
pp. 193 ◽  
Author(s):  
Hossein Bagheri ◽  
Michael Schmitt ◽  
Xiaoxiang Zhu
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Point Clouds ◽  
Original Data ◽  
Markup Language ◽  
Geography Markup Language ◽  
Building Models ◽  
Extensive Coverage ◽  
Constant Height ◽  
Digital Elevation

So-called prismatic 3D building models, following the level-of-detail (LOD) 1 of the OGC City Geography Markup Language (CityGML) standard, are usually generated automatically by combining building footprints with height values. Typically, high-resolution digital elevation models (DEMs) or dense LiDAR point clouds are used to generate these building models. However, high-resolution LiDAR data are usually not available with extensive coverage, whereas globally available DEM data are often not detailed and accurate enough to provide sufficient input to the modeling of individual buildings. Therefore, this paper investigates the possibility of generating LOD1 building models from both volunteered geographic information (VGI) in the form of OpenStreetMap data and remote sensing-derived geodata improved by multi-sensor and multi-modal DEM fusion techniques or produced by synthetic aperture radar (SAR)-optical stereogrammetry. The results of this study show several things: First, it can be seen that the height information resulting from data fusion is of higher quality than the original data sources. Secondly, the study confirms that simple, prismatic building models can be reconstructed by combining OpenStreetMap building footprints and easily accessible, remote sensing-derived geodata, indicating the potential of application on extensive areas. The building models were created under the assumption of flat terrain at a constant height, which is valid in the selected study area.

Pre-landslide topographic reconstruction using a Digital Elevation Model from CaSSIS onboard the Trace Gas Orbiter.

2021 ◽  
Author(s):  
Anthony Guimpier ◽  
Susan Conway ◽  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Emanuele Simioni ◽  
...  
Keyword(s):  
High Resolution ◽  
Imaging System ◽  
Three Dimensional ◽  
Vertical Resolution ◽  
Topographic Data ◽  
Contour Lines ◽  
Digital Elevation ◽  
Landslide Event ◽  
Imaging Science ◽  
Topographic Reconstruction

&lt;p&gt;Landslides are common features on the surface of Mars. They have morphologies that resemble debris slides, mudflows [1], or giant rock avalanches [e.g., 2] on Earth. They can mobilise large quantities of material up to 10&lt;sup&gt;12&lt;/sup&gt; m&lt;sup&gt;3&lt;/sup&gt; and spread over areas of up to 10&lt;sup&gt;9&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt; [e.g., 3].&lt;/p&gt;&lt;p&gt;The topography before the landslide event occurred is required to both estimate the volume of mobilised material and quantify the distribution and thickness of the deposit. The mass distribution of the deposit can also be used to compare with 3D flow simulations of landslides [e.g. 1, 3]. However, on Mars there are no landslides that have known topographic data before the event occurred, hence we have to rely on topographic reconstruction.&lt;/p&gt;&lt;p&gt;This type of reconstruction, which we have already carried out using HiRISE (High Resolution Imaging Science Experiment) Digital Elevation Models (DEM) with 1-2 m vertical resolution [e.g., 1], has never been undertaken using DEMs with 4-5 m vertical resolution derived from CaSSIS (Colour and Stereo Surface Imaging System) stereo pairs [4]. CaSSIS uses a 180&amp;#176; camera rotation to capture stereo images of a given site in a single pass. DEMs are then generated using 3DPD (three Dimensional reconstruction of Planetary Data) software [5].&lt;/p&gt;&lt;p&gt;Our aim is to test whether a landslide reconstruction can be carried out with a CaSSIS DEM. For our purpose we use a 6&amp;#160;km long landslide in Baetis Chaos region, Mars.&lt;/p&gt;&lt;p&gt;Our reconstruction consists of three main steps: 1) We first calculate contour lines. 2) Reconstructed contour lines are then drawn by connecting contour lines on either side of the boundary taking into account the overall topography outside the landslide. 3) Then, the reconstructed contour lines are converted into points at intervals equal to the spatial resolution of the DEM. These points are then interpolated using a natural neighbour algorithm to calculate a new DEM without the landslide. We were able to estimate that the landslide in Baetis Chaos has a volume of 10&lt;sup&gt;8&lt;/sup&gt;&amp;#160;m&lt;sup&gt;3&lt;/sup&gt; and the deposit has a maximum thickness of 200&amp;#160;m using CaSSIS data.&lt;/p&gt;&lt;p&gt;Our successful reconstruction using a CaSSIS DEM increases the potential coverage of high-resolution stereo-topographic data beyond those already available with CTX and/or HiRISE. The resolution CaSSIS DEMs fills a gap in the topographic data currently available for studying landslides. Landslides &gt; 15&amp;#160;km long can be studied with MOLA or HRSC data, and landslides &lt; 5 km long can be studied using HiRISE data. Now, landslides and other landforms 5-15&amp;#160;km can be studied using CaSSIS data with equivalent quality to CTX stereo-topography.&lt;/p&gt;&lt;p&gt;Acknowledgement:&amp;#160;CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova&amp;#160;(ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.&lt;/p&gt;&lt;p&gt;References: [1] A. Guimpier et al. (In review) &lt;em&gt;PSS&lt;/em&gt;. [2] G. Magnarini et al. (2019) &lt;em&gt;Nature Communications&lt;/em&gt;. [3] G.B. Crosta et al. (2018) &lt;em&gt;ESS&lt;/em&gt;, 5, 89&amp;#8211;119. [4] A. Lucas et al. (2014) &lt;em&gt;Nature Communications&lt;/em&gt;. [5] E. Simioni et al. (In press) &lt;em&gt;PSS&lt;/em&gt;.&lt;/p&gt;

scholarly journals Determining the optimal grid resolution for topographic analysis on an airborne lidar dataset

2019 ◽  
Vol 7 (2) ◽  
pp. 475-489 ◽  
Author(s):  
Taylor Smith ◽  
Aljoscha Rheinwalt ◽  
Bodo Bookhagen
Keyword(s):  
Synthetic Data ◽  
Airborne Lidar ◽  
Grid Resolution ◽  
Slope Aspect ◽  
Topographic Analysis ◽  
Quality Metric ◽  
Digital Elevation ◽  
Uncertainty Estimates ◽  
Point Density ◽  
Dem Uncertainty

Abstract. Digital elevation models (DEMs) are a gridded representation of the surface of the Earth and typically contain uncertainties due to data collection and processing. Slope and aspect estimates on a DEM contain errors and uncertainties inherited from the representation of a continuous surface as a grid (referred to as truncation error; TE) and from any DEM uncertainty. We analyze in detail the impacts of TE and propagated elevation uncertainty (PEU) on slope and aspect. Using synthetic data as a control, we define functions to quantify both TE and PEU for arbitrary grids. We then develop a quality metric which captures the combined impact of both TE and PEU on the calculation of topographic metrics. Our quality metric allows us to examine the spatial patterns of error and uncertainty in topographic metrics and to compare calculations on DEMs of different sizes and accuracies. Using lidar data with point density of ∼10 pts m−2 covering Santa Cruz Island in southern California, we are able to generate DEMs and uncertainty estimates at several grid resolutions. Slope (aspect) errors on the 1 m dataset are on average 0.3∘ (0.9∘) from TE and 5.5∘ (14.5∘) from PEU. We calculate an optimal DEM resolution for our SCI lidar dataset of 4 m that minimizes the error bounds on topographic metric calculations due to the combined influence of TE and PEU for both slope and aspect calculations over the entire SCI. Average slope (aspect) errors from the 4 m DEM are 0.25∘ (0.75∘) from TE and 5∘ (12.5∘) from PEU. While the smallest grid resolution possible from the high-density SCI lidar is not necessarily optimal for calculating topographic metrics, high point-density data are essential for measuring DEM uncertainty across a range of resolutions.

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