scholarly journals Probabilistic Model of Random Encounter in Obstacle Space

2019 ◽  
Vol 8 (1) ◽  
pp. 32
Author(s):  
Zhang-Cai Yin ◽  
Hui Liu ◽  
Zhi-Jun Zhang ◽  
Zhang-Hao-Nan Jin ◽  
San-Juan Li ◽  
...  
Keyword(s):  
Moving Objects ◽  
Time Geography ◽  
Temporal And Spatial Distribution ◽  
Encounter Probability ◽  
Mobile Objects ◽  
Geographical Environment ◽  
Digital Elevation ◽  
Wide Range ◽  
Quantitative Basis ◽  
Elevation Model

Based on probabilistic time-geography, the encounter between two moving objects is random. The quantitative analysis of the probability of encounter needs to consider the actual geographical environment. The existing encounter probability algorithm is based on homogeneous space, ignoring the wide range of obstacles and their impact on encounter events. Based on this, this paper introduces obstacle factors, proposes encounter events that are constrained by obstacles, and constructs a model of the probability of encounters of moving objects based on the influence of obstacles on visual perception with the line-of-sight view analysis principle. In realistic obstacle space, this method provides a quantitative basis for predicting the encountering possibility of two mobile objects and the largest possible encounter location. Finally, the validity of the model is verified by experimental results. The model uses part of the Wuhan digital elevation model (DEM) data to calculate the encounter probability of two moving objects on it, and analyzes the temporal and spatial distribution characteristics of these probabilities.

scholarly journals Mobility characteristics of debris slides and flows triggered by Hurricane Maria in Puerto Rico

Landslides ◽  
2020 ◽  
Vol 17 (12) ◽  
pp. 2795-2809 ◽  
Author(s):  
Erin K. Bessette-Kirton ◽  
Jeffrey A. Coe ◽  
William H. Schulz ◽  
Corina Cerovski-Darriau ◽  
Mason M. Einbund
Keyword(s):  
Puerto Rico ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Source Areas ◽  
Tropical Environments ◽  
Digital Elevation ◽  
Wide Range ◽  
Hazard And Risk ◽  
Elevation Model ◽  
Landslides And Debris Flows

Abstract Mobility is an important element of landslide hazard and risk assessments yet has been seldom studied for shallow landslides and debris flows in tropical environments. In September 2017, Hurricane Maria triggered > 70,000 landslides across Puerto Rico. Using aerial imagery and a lidar digital elevation model (DEM), we mapped and characterized the mobility of debris slides and flows in four different geologic materials: (1) mudstone, siltstone, and sandstone; (2) submarine basalt and chert; (3) marine volcaniclastics; and (4) granodiorite. We used the ratio of landslide-fall height (H) to travel length (L), H/L, to assess the mobility of landslides in each material. Additionally, we differentiated between landslides with single and multiple source areas and landslides that either did or did not enter drainages. Overall, extreme rainfall contributed to the mobility of landslides during Hurricane Maria, and our results showed that the mobility of debris slides and flows in Puerto Rico increased linearly as a function of the number of source areas that coalesced. Additionally, landslides that entered drainages were more mobile than those that did not. We found that landslides in soils developed on marine volcaniclastics were the most mobile and landslides in soils on submarine basalt and chert were the least mobile. While landslides were generally small (< 100 m2) and displayed a wide range of H/L values (0.1–2), coalescence increased the mobility of landslides that transitioned to debris flows. The high but variable mobility of landslides that occurred during Hurricane Maria and the associated hazards highlight the importance of characterizing and understanding the factors influencing landslide mobility in Puerto Rico and other tropical environments.

scholarly journals Comparison of Vertical Accuracy of Open-Source Global Digital Elevation Models: A Case Study of Adama City, Ethiopia

2021 ◽  
Vol 12 (4) ◽  
pp. 1731-1744
Author(s):  
Hailu Zewde Abili
Keyword(s):  
Open Source ◽  
Thermal Emission ◽  
Accuracy Assessment ◽  
Shuttle Radar Topography Mission ◽  
Surface Model ◽  
Aster Gdem ◽  
Digital Elevation ◽  
Wide Range ◽  
Vertical Accuracy ◽  
Elevation Model

DEM can be generated from a wide range of sources including land surveys, Photogrammetry, and Remote sensing satellites. SRTM 30m DEM by The Shuttle Radar Topography Mission (SRTM), the Global Digital Elevation Model by Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER GDEM) and a global surface model called ALOS Worldview 3D 30 meter (AW3D30) by Advanced Land Observing Satellite (ALOS) are satellite-based global DEMs open-source DEM datasets. This study aims to assess the vertical accuracy of ASTER GDEM2, SRTM 30m, and ALOS (AW3D30) global DEMs over Ethiopia in the study area-Adama by using DGPS points and available accurate reference DEM data. The method used to evaluate the vertical accuracy of those DEMs ranges from simple visual comparison to relative and absolute comparisons providing quantitative assessment (Statistical) that used the elevation differences between DEM datasets and reference datasets. The result of this assessment showed better accuracy of SRTM 30m DEM (having RMSE of ± 4.63 m) and closely followed by ALOS (AW3D30) DEM which scored RMSE of ± 5.25 m respectively. ASTER GDEM 2 showed the least accuracy by scoring RMSE of ± 11.18 m in the study area. The second accuracy assessment was done by the analysis of derived products such as slope and drainage networks. This also resulted in a better quality of DEM derived products for SRTM than ALOS DEM and ASTER GDEM.

scholarly journals Distance-Decay Effect in Probabilistic Time Geography for Random Encounter

2019 ◽  
Vol 8 (4) ◽  
pp. 177
Author(s):  
Zhang-Cai Yin ◽  
Zhang-Hao-Nan Jin ◽  
Shen Ying ◽  
Hui Liu ◽  
San-Juan Li ◽  
...  
Keyword(s):  
Moving Objects ◽  
Probability Model ◽  
Distance Decay ◽  
Time Geography ◽  
Distance Threshold ◽  
Encounter Probability ◽  
Proposed Model ◽  
Measure Model ◽  
Definition Of ◽  
Decay Effect

Probabilistic time geography uses a fixed distance threshold for the definition of the encounter events of moving objects. However, because of the distance-decay effect, different distances within the fixed threshold ensure that the encounter events do not always have the same possibility, and, therefore, the quantitative probabilistic time geography analysis needs to consider the actual distance-decay coefficient (DDC). Thus, this paper introduces the DDC and proposes a new encounter probability measure model that takes into account the distance-decay effect. Given two positions of a pair of moving objects, the traditional encounter probability model is that if the distance between the two positions does not exceed a given threshold, the encounter event may occur, and its probability is equal to the product of the probabilities of the two moving objects in their respective positions. Furthermore, the probability of the encounter at two given positions is multiplied by the DDC in the proposed model, in order to express the influence of the distance-decay effect on the encounter probability. Finally, the validity of the proposed model is verified by an experiment, which uses the tracking data of wild zebras to calculate the encounter probability, and compares it with the former method.

scholarly journals AN IMPROVED DEM CONSTRUCTION METHOD FOR MUDFLATS BASED ON BJ-1 SMALL SATELLITE IMAGES: A CASE STUDY ON BOHAI BAY

2018 ◽  
Vol XLII-3 ◽  
pp. 1871-1878 ◽  
Author(s):  
D. Wu ◽  
Y. Du ◽  
F. Su ◽  
W. Huang ◽  
L. Zhang
Keyword(s):  
Satellite Images ◽  
Evaluation Model ◽  
Ocean Tide ◽  
Bohai Bay ◽  
Small Satellite ◽  
Detection Model ◽  
Digital Elevation ◽  
Wide Range ◽  
Multi Temporal ◽  
Elevation Model

The topographic measurement of muddy tidal flat is restricted by the difficulty of access to the complex, wide-range and dynamic tidal conditions. Then the waterline detection method (WDM) has the potential to investigate the morph-dynamics quantitatively by utilizing large archives of satellite images. The study explores the potential for using WDM with BJ-1 small satellite images to construct a digital elevation model (DEM) of a wide and grading mudflat. Three major conclusions of the study are as follows: (1) A new intelligent correlating model of waterline detection considering different tidal stages and local geographic conditions was explored. With this correlative algorithm waterline detection model, a series of waterlines were extracted from multi-temporal remotely sensing images collected over the period of a year. The model proved to detect waterlines more efficiently and exactly. (2) The spatial structure of elevation superimposing on the points of waterlines was firstly constructed and a more accurate hydrodynamic ocean tide grid model was used. By the newly constructed abnormal hydrology evaluation model, a more reasonable and reliable set of waterline points was acquired to construct a smoother TIN and GRID DEM. (3) DEM maps of Bohai Bay, with a spatial resolution of about 30&amp;thinsp;m and height accuracy of about 0.35&amp;thinsp;m considering LiDAR and 0.19&amp;thinsp;m considering RTK surveying were constructed over an area of about 266&amp;thinsp;km<sup>2</sup>. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible and is an effective tool for monitoring the tidal flats.

Distance Transforms as a New Tool in Spatial Analysis, Urban Planning, and GIS

2004 ◽  
Vol 31 (1) ◽  
pp. 85-104 ◽  
Author(s):  
Michael J de Smith
Keyword(s):  
Spatial Analysis ◽  
Location Theory ◽  
Continuous Space ◽  
Distance Transforms ◽  
Digital Elevation ◽  
Wide Range ◽  
Standard Set ◽  
Elevation Model ◽  
Digital Elevation Model Data ◽  
2D And 3D

Many spatial datasets and spatial problems can be described with reference to regular lattice frameworks rather than continuous space. Examples include: raster scan and digital elevation model data, digital images, cost surfaces, cellular automata models, swarm models, and many others. This raises the question as to how distances should be measured in such cases and to what extent these relate to continuous space metrics. In this paper I show that a set of image processing algorithms known as distance transforms (DTs) may be applied to such datasets and can be extended to solve a wide range of 2D and 3D optimisation problems. These extended versions of the standard DT procedure have applications in many areas including location theory, path determination, planning, and decision support. As such I argue that they warrant consideration for inclusion as a standard set of tools within modern GIS and spatial analysis software packages. Sample pseudo-code for the transforms discussed is included in an appendix.

scholarly journals Testing Different Interpolation Methods Based on Single Beam Echosounder River Surveying. Case Study: Siret River

2019 ◽  
Vol 8 (11) ◽  
pp. 507 ◽  
Author(s):  
Arseni ◽  
Voiculescu ◽  
Georgescu ◽  
Iticescu ◽  
Rosu
Keyword(s):  
Cross Sections ◽  
Interpolation Method ◽  
Morphological Changes ◽  
Numerical Models ◽  
Entire Area ◽  
Single Beam ◽  
Interpolation Methods ◽  
Digital Elevation ◽  
Wide Range ◽  
Elevation Model

Bathymetric measurements play an important role in assessing the sedimentation rate, deposition of pollutants, erosion rate, or monitoring of morphological changes in a river, lake, or accumulation basin. In order to create a coherent and continuous digital elevation model (DEM) of a river bed, various data interpolation methods are used, especially when single-beam bathymetric measurements do not cover the entire area and when there are areas which are not measured. Interpolation methods are based on numerical models applied to natural landscapes (e.g., meandering river) by taking into account various morphometric and morphologies and a wide range of scales. Obviously, each interpolation method, used in standard or customised form, yields different results. This study aims at testing four interpolation methods in order to determine the most appropriate method which will give an accurate description of the riverbed, based on single-beam bathymetric measurements. The four interpolation methods selected in the present research are: inverse distance weighting (IDW), radial basis function (RBF) with completely regularized spline (CRS) which uses deterministic interpolation, simple kriging (KRG) which is a geo-statistical method, and Topo to Raster (TopoR), a particular method specifically designed for creating continuous surfaces from various elevation points, contour, or polygon data, suitable for creating surfaces for hydrologic analysis. Digital elevation models (DEM’s) were statistically analyzed and precision and errors were evaluated. The single-beam bathymetric measurements were made on the Siret River, between 0 and 35 km. To check and validate the methods, the experiment was repeated for five randomly selected cross-sections in a 1500 m section of the river. The results were then compared with the data extracted from each elevation model generated with each of the four interpolation methods. Our results show that: 1) TopoR is the most accurate technique, and 2) the two deterministic methods give large errors in bank areas, for the entire river channel and for the particular cross-sections.

scholarly journals Accuracy Assessment of Digital Elevation Models Using GPS

2008 ◽  
Vol 43 (4) ◽  
pp. 151-161 ◽  
Author(s):  
Ashraf Farah ◽  
Ashraf Talaat ◽  
Farrag Farrag
Keyword(s):  
Laser Scanning ◽  
Accuracy Assessment ◽  
Digital Elevation Models ◽  
Ground Surface ◽  
Digital Elevation ◽  
Wide Range ◽  
Military Planning ◽  
Rms Error ◽  
Elevation Model ◽  
Application Fields

Accuracy Assessment of Digital Elevation Models Using GPSA Digital Elevation Model (DEM) is a digital representation of ground surface topography or terrain with different accuracies for different application fields. DEM have been applied to a wide range of civil engineering and military planning tasks. DEM is obtained using a number of techniques such as photogrammetry, digitizing, laser scanning, radar interferometry, classical survey and GPS techniques. This paper presents an assessment study of DEM using GPS (Stop&Go) and kinematic techniques comparing with classical survey. The results show that a DEM generated from (Stop&Go) GPS technique has the highest accuracy with a RMS error of 9.70 cm. The RMS error of DEM derived by kinematic GPS is 12.00 cm.

scholarly journals A new 1 km digital elevation model of Antarctica derived from combined radar and laser data – Part 2: Validation and error estimates

2009 ◽  
Vol 3 (1) ◽  
pp. 113-123 ◽  
Author(s):  
J. A. Griggs ◽  
J. L. Bamber
Keyword(s):  
Digital Elevation Model ◽  
Satellite Data ◽  
Ice Sheet ◽  
Multiple Linear Regression Model ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Digital Elevation ◽  
Surface Slopes ◽  
Wide Range ◽  
Elevation Model

Abstract. We have developed a new digital elevation model (DEM) of Antarctica from a combination of satellite radar and laser altimeter data. Here, we assess the accuracy of the DEM by comparison with airborne altimeter data from four campaigns covering a wide range of surface slopes and ice sheet regions. Root mean squared (RMS) differences varied from 4.75 m, when compared to a densely gridded airborne dataset over the Siple Coast region of West Antarctica to 33.78 m when compared to a more limited dataset over the Antarctic Peninsula where surface slopes are high and the across track spacing of the satellite data is relatively large. The airborne data sets were employed to produce an error map for the DEM by developing a multiple linear regression model based on the variables known to influence errors in the DEM. Errors were found to correlate highly with surface slope, roughness and density of satellite data points. Errors ranged from typically ~1 m over the ice shelves to between about 2 and 6 m for the majority of the grounded ice sheet. In the steeply sloping margins, along the Peninsula and mountain ranges the estimated error is several tens of metres. Less than 2% of the area covered by the satellite data had an estimated random error greater than 20 m.

scholarly journals A new 1 km digital elevation model of Antarctica derived from combined radar and laser data – Part 2: Validation and error estimates

2008 ◽  
Vol 2 (5) ◽  
pp. 843-872 ◽  
Author(s):  
J. A. Griggs ◽  
J. L. Bamber
Keyword(s):  
Digital Elevation Model ◽  
Satellite Data ◽  
Ice Sheet ◽  
Multiple Linear Regression Model ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Digital Elevation ◽  
Surface Slopes ◽  
Wide Range ◽  
Elevation Model

Abstract. We have developed a new digital elevation model (DEM) of Antarctica from a combination of satellite radar and laser altimeter data. Here, we assess the accuracy of the DEM by comparison with airborne altimeter data from four campaigns covering a wide range of surface slopes and ice sheet regions. RMS differences varied from 4.84 m, when compared to a densely gridded airborne dataset over the Siple Coast region of West Antarctica to 29.28 m when compared to a more limited dataset over the Antarctic Peninsula where surface slopes are high and the across track spacing of the satellite data is relatively large. The airborne data sets were employed to produce an error map for the DEM by developing a multiple linear regression model based on the variables known to influence errors in the DEM. Errors were found to correlate highly with surface slope, roughness and density of satellite data points. Errors ranged from typically ~1 m over the ice shelves to between about 4 and 10 m for the majority of the grounded ice sheet. In the steeply sloping margins, along the Peninsula and mountain ranges the estimated error is several tens of metres. Slightly less than 7% of the area covered by the satellite data had an estimated random error greater than 20 m.

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