scholarly journals Influence of temporal baseline on the vertical absolute accuracies of TSX HS interferometric DSMs: Case Study on Berlin

2014 ◽  
Vol XL-7 ◽  
pp. 155-160
Author(s):  
U. G. Sefercik ◽  
U. Soergel
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Negative Influence ◽  
Absolute Accuracy ◽  
Surface Models ◽  
Sar Imagery ◽  
Image Pairs ◽  
Better Than ◽  
Aperture Radar

In recent years, interferometric sytnthetic aperture radar (InSAR) is one of the most preferred techniques to generate digital surface models (DSM) which are the three dimensional (3D) digital cartographic representations of earth surface including all terrain and non-terrain formations. Interferometric DSM generation using synthetic aperture radar (SAR) imagery is not an easy process and the vertical absolute accuracy of the final product depends on various parameters. In this study, we aimed to demonstrate the influence of temporal baseline between SAR image-pairs on the vertical absolute accuracy of high resolution interferometric DSMs. The application was realized covering 20 km<sup>2</sup> area in Berlin, Germany using 15 descending orbit high resolution spotlight (HS) TerraSAR-X (TSX) images. The suitable interferometric pairs were determined for DSM generation and two of them that have similar parameters except temporal baseline were selected regarding the purposes of the study. The master image was selected as same in the generation of both DSMs and the temporal baselines between this master image and slave images were 11 days (1 period) and 187 days (17 periods), respectively. TSX HS DSMs were generated with 2 m grid spacing and the vertical absolute accuracies were calculated based on the comparison with a reference DSM generated by radargrammetry. The analyses were realized for built-up and forest land classes separately. The results proved that longer temporal baseline has negative influence on the vertical absolute accuracies of TSX HS interferometric DSMs. The first DSM which has the shortest temporal baseline, possible for TSX sensing is better than the second one as approx. 1.5 m both for built-up and forest areas.

scholarly journals The Use of Similarity Concepts to Represent Subgrid Variability in Land Surface Models: Case Study in a Snowmelt-Dominated Watershed

2014 ◽  
Vol 15 (5) ◽  
pp. 1717-1738 ◽  
Author(s):  
Andrew J. Newman ◽  
Martyn P. Clark ◽  
Adam Winstral ◽  
Danny Marks ◽  
Mark Seyfried
Keyword(s):  
High Resolution ◽  
Land Surface ◽  
Mesoscale Model ◽  
A Priori ◽  
Land Surface Models ◽  
Creek Watershed ◽  
Surface Models ◽  
Reynolds Creek ◽  
Better Than

Abstract This paper develops a multivariate mosaic subgrid approach to represent subgrid variability in land surface models (LSMs). The k-means clustering is used to take an arbitrary number of input descriptors and objectively determine areas of similarity within a catchment or mesoscale model grid box. Two different classifications of hydrologic similarity are compared: an a priori classification, where clusters are based solely on known physiographic information, and an a posteriori classification, where clusters are defined based on high-resolution LSM simulations. Simulations from these clustering approaches are compared to high-resolution gridded simulations, as well as to three common mosaic approaches used in LSMs: the “lumped” approach (no subgrid variability), disaggregation by elevation bands, and disaggregation by vegetation types in two subcatchments. All watershed disaggregation methods are incorporated in the Noah Multi-Physics (Noah-MP) LSM and applied to snowmelt-dominated subcatchments within the Reynolds Creek watershed in Idaho. Results demonstrate that the a priori clustering method is able to capture the aggregate impact of finescale spatial variability with O(10) simulation points, which is practical for implementation into an LSM scheme for coupled predictions on continental–global scales. The multivariate a priori approach better represents snow cover and depth variability than the univariate mosaic approaches, critical in snowmelt-dominated areas. Catchment-averaged energy fluxes are generally within 10%–15% for the high-resolution and a priori simulations, while displaying more subgrid variability than the univariate mosaic methods. Examination of observed and simulated streamflow time series shows that the a priori method generally reproduces hydrograph characteristics better than the simple disaggregation approaches.

scholarly journals The Baseline Metrology System of the USNO Astrometric Interferometer

1994 ◽  
Vol 158 ◽  
pp. 174-176 ◽  
Author(s):  
Nicholas M. Elias ◽  
Donald J. Hutter
Keyword(s):  
High Resolution ◽  
Northern Hemisphere ◽  
Three Dimensional ◽  
Optical Interferometer ◽  
Laser Metrology ◽  
Under Construction ◽  
Metrology System ◽  
Better Than

The USNO Astrometric Interferometer (USNOAI; a subarray of the Navy Prototype Optical Interferometer at Lowell Observatory) is presently under construction and expected to begin limited operations within a year. The main goal of the USNOAI observations is to provide a northern hemisphere catalog of several thousand stars with positions known to a few mas. In order to meet this requirement, a baseline laser metrology system must be employed to measure the three-dimensional motions of the baselines with an accuracy better than ~ 0.1 μm. The metrology scheme, as presently conceived, represents the largest and most complex high-resolution laser metrology system ever attempted.

scholarly journals Three-Dimensional Reconstruction of Structural Surface Model of Heritage Bridges Using UAV-Based Photogrammetric Point Clouds

2019 ◽  
Vol 11 (10) ◽  
pp. 1204 ◽  
Author(s):  
Yue Pan ◽  
Yiqing Dong ◽  
Dalei Wang ◽  
Airong Chen ◽  
Zhen Ye
Keyword(s):  
Classification Tree ◽  
Three Dimensional ◽  
Point Clouds ◽  
3D Models ◽  
Surface Model ◽  
Reconstruction Method ◽  
3D Point Clouds ◽  
Surface Models ◽  
Structural Surface ◽  
Better Than

Three-dimensional (3D) digital technology is essential to the maintenance and monitoring of cultural heritage sites. In the field of bridge engineering, 3D models generated from point clouds of existing bridges is drawing increasing attention. Currently, the widespread use of the unmanned aerial vehicle (UAV) provides a practical solution for generating 3D point clouds as well as models, which can drastically reduce the manual effort and cost involved. In this study, we present a semi-automated framework for generating structural surface models of heritage bridges. To be specific, we propose to tackle this challenge via a novel top-down method for segmenting main bridge components, combined with rule-based classification, to produce labeled 3D models from UAV photogrammetric point clouds. The point clouds of the heritage bridge are generated from the captured UAV images through the structure-from-motion workflow. A segmentation method is developed based on the supervoxel structure and global graph optimization, which can effectively separate bridge components based on geometric features. Then, recognition by the use of a classification tree and bridge geometry is utilized to recognize different structural elements from the obtained segments. Finally, surface modeling is conducted to generate surface models of the recognized elements. Experiments using two bridges in China demonstrate the potential of the presented structural model reconstruction method using UAV photogrammetry and point cloud processing in 3D digital documentation of heritage bridges. By using given markers, the reconstruction error of point clouds can be as small as 0.4%. Moreover, the precision and recall of segmentation results using testing date are better than 0.8, and a recognition accuracy better than 0.8 is achieved.

scholarly journals Evaluating the Environmental Performance of 3D Printed Shelters in Jordan

2021 ◽  
Vol 26 (2) ◽  
pp. 117-134
Author(s):  
Mohanad Akeila ◽  
Christopher Preece ◽  
King Kuok Kelvin Kuok
Keyword(s):  
Environmental Performance ◽  
Three Dimensional ◽  
Huge Number ◽  
Electricity Cost ◽  
Internal Conflicts ◽  
Research Article ◽  
3D Printed ◽  
Ventilation Rates ◽  
Better Than

Three-dimensional (3D) printed shelters are an innovative housing solution for those in need of a shelter after a disaster. The Middle East generated a huge number of refugees due to internal conflicts. The technology has been investigated earlier from a cost and time perspectives and has performed better than steel shelters in Jordan. This research article investigates environmental performance of 3D printed shelters in Jordan in terms of energy, fuel, cooling and ventilation. Syrian refugees of Jordanian camps were selected as a case study. The energy simulation of the steel shelter to that of a printed shelter showed that the latter can achieve higher ventilation rates, lower energy consumption, less electricity cost and better thermal insulation than steel shelters.

scholarly journals AN IMPROVED INTERFEROMETRIC CALIBRATION METHOD BASED ON INDEPENDENT PARAMETER DECOMPOSITION

2018 ◽  
Vol XLII-3 ◽  
pp. 321-327
Author(s):  
J. Fan ◽  
X. Zuo ◽  
T. Li ◽  
Q. Chen ◽  
X. Geng
Keyword(s):  
Three Dimensional ◽  
Calibration Method ◽  
Shanxi Province ◽  
Independent Parameter ◽  
Mountainous Area ◽  
Calibration Model ◽  
Flat Area ◽  
Image Pairs ◽  
Interferometric Sar ◽  
Better Than

Interferometric SAR is sensitive to earth surface undulation. The accuracy of interferometric parameters plays a significant role in precise digital elevation model (DEM). The interferometric calibration is to obtain high-precision global DEM by calculating the interferometric parameters using ground control points (GCPs). However, interferometric parameters are always calculated jointly, making them difficult to decompose precisely. In this paper, we propose an interferometric calibration method based on independent parameter decomposition (IPD). Firstly, the parameters related to the interferometric SAR measurement are determined based on the three-dimensional reconstruction model. Secondly, the sensitivity of interferometric parameters is quantitatively analyzed after the geometric parameters are completely decomposed. Finally, each interferometric parameter is calculated based on IPD and interferometric calibration model is established. We take Weinan of Shanxi province as an example and choose 4 TerraDEM-X image pairs to carry out interferometric calibration experiment. The results show that the elevation accuracy of all SAR images is better than 2.54&amp;thinsp;m after interferometric calibration. Furthermore, the proposed method can obtain the accuracy of DEM products better than 2.43&amp;thinsp;m in the flat area and 6.97&amp;thinsp;m in the mountainous area, which can prove the correctness and effectiveness of the proposed IPD based interferometric calibration method. The results provide a technical basis for topographic mapping of 1&amp;thinsp;:&amp;thinsp;50000 and even larger scale in the flat area and mountainous area.

Airborne Structure-from-Motion modelling for avalanche and debris flow paths in steep terrain with limited ground control

2020 ◽  
Author(s):  
Sean Salazar ◽  
Helge Smebye ◽  
Regula Frauenfelder ◽  
Frank Miller ◽  
Emil Solbakken ◽  
...  
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Case Studies ◽  
Structure From Motion ◽  
Ground Control ◽  
Surface Model ◽  
Flight Plan ◽  
Surface Models ◽  
Steep Terrain

&lt;p&gt;The availability of consumer remotely piloted aircraft systems (RPAS) has enabled rapidly deployable airborne surveys for civilian applications. Combined with photogrammetric reconstruction techniques, such as Structure-from-Motion (SfM), it has become increasingly feasible to survey large areas with very high resolution, especially when compared with other airborne or spaceborne surveying techniques. A pair of case studies, using an RPAS-based field surveying technique for establishing baseline surface models in steep terrain, are presented for two different natural hazard applications.&lt;/p&gt;&lt;p&gt;The first case study involved a survey over the entire 1000-m length of a snow-free avalanche path on S&amp;#230;treskarsfjellet in Stryn municipality in Norway. A terrain-aware, multi-battery flight plan was designed to ensure good photographic coverage over the entire avalanche path and 21 ground control points (GCP) were distributed evenly across the path and subsequently surveyed. More than 400 images were collected over a 0.5 km&lt;sup&gt;2&lt;/sup&gt; area, which were processed using a commercial SfM software package. Two digital surface models were reconstructed, each utilizing a different ground control scenario: the first one with the full count of GCP, while the second used only a limited count of GCP, which is more feasible for a repeat survey when avalanche hazard is high. Comparison with data from a pre-existing, airborne LiDAR survey over the avalanche path revealed that the SfM-derived model that utilized only a limited number of GCP diverged significantly from the model that utilized all available GCP. Further differences between the SfM- and LiDAR-derived surface models were observed in areas with very steep slopes and vegetative cover. The same methodology can subsequently be applied during the winter season, after extensive snowfall and/or avalanche events, to deduce relevant avalanche parameters such as snow height, snow distribution and drift, opening of cracks in the snow surface (e.g. for glide avalanches), and avalanche outlines.&lt;/p&gt;&lt;p&gt;The second case study involved a survey over the entire 1000-m length of a debris flow path at &amp;#197;rnes in J&amp;#248;lster, Norway. The &amp;#197;rnes flow, which caused one fatality, was one of the largest of several tens of debris flows that occurred on July 30, 2019. The flows were triggered by an extreme precipitation event around the J&amp;#248;lstravatnet area. Like with the S&amp;#230;treskarsfjellet avalanche path case study, a terrain-aware flight plan was established and 24 GCP were distributed and surveyed along the debris flow path. Over 400 images were collected over a 0.3 km&lt;sup&gt;2&lt;/sup&gt; area, which were used to reconstruct a high-resolution surface model. Like with the avalanche case study, the SfM-derived model was compared with a pre-existing LiDAR survey-derived digital terrain model. Altitude and volume changes, due to the debris flow event, were calculated using GIS analysis tools.&lt;/p&gt;&lt;p&gt;The utility of the RPAS survey technique was demonstrated in both case studies, despite difficult accessibility for ground control. It is suggested that a real-time-kinematic (RTK)-enabled workflow may significantly reduce survey time and increase personnel safety by minimizing the number of required GCP.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Structure-from-Motion, photogrammetry, digital surface model, natural hazards, ground control.&lt;/p&gt;

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