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The General Allotment Act of 1887, also known as the Dawes Act, established the legal basis for the United States government to break up remaining tribally-owned reservation lands in the U.S. by allotting individual parcels to tribal members and selling the remaining “surplus.” This research explores the processes involved in mapping these historical allotments and describes a method to automatically generate spatial data of allotments. A custom geographic information systems (GIS) tool was created that takes tabular based allotment land descriptions and digital Public Land Survey (PLSS) databases to automatically generate spatial and attribute data of those land parcels. The Standing Rock Sioux Tribe of North and South Dakota was used as the initial study area to test the mapping technique, which resulted in successfully auto-mapping over 99.1% of allotted lands on the reservation, including the smallest aliquot parcels. This GIS technique can be used to map any tribal lands or reservation with allotment data available, and currently it can be used to map over 120 individual reservations using publicly available data from the Bureau of Land Management (BLM).
Joshua Meisel; Stephen Egbert; Joseph Brewer; Xingong Li. Automated Mapping of Historical Native American Land Allotments at the Standing Rock Sioux Reservation Using Geographic Information Systems. ISPRS International Journal of Geo-Information 2021, 10, 183 .
AMA StyleJoshua Meisel, Stephen Egbert, Joseph Brewer, Xingong Li. Automated Mapping of Historical Native American Land Allotments at the Standing Rock Sioux Reservation Using Geographic Information Systems. ISPRS International Journal of Geo-Information. 2021; 10 (3):183.
Chicago/Turabian StyleJoshua Meisel; Stephen Egbert; Joseph Brewer; Xingong Li. 2021. "Automated Mapping of Historical Native American Land Allotments at the Standing Rock Sioux Reservation Using Geographic Information Systems." ISPRS International Journal of Geo-Information 10, no. 3: 183.
Global climates have been warming over the past four decades, with many implications and effects on species and natural communities, in terms of shifts in geographic and elevational ranges. Nonetheless, major knowledge gaps exist, particularly for tropical regions, as regards the timescale and rate of range shifts. We used Landsat imagery to characterize the upper limits of forest and of bunch grassland on the 15 highest (>3500 m) volcanoes of central Mexico over three decades (1986–2018), and documented upward vegetation shifts averaging >490 m in elevation over this period. Treelines showed upward shifts averaging 17.3 m/year over 1986–2018; for one eastern Mexican volcano (Sierra Negra), the NDVI‐based rate (35.7 m/year) contrasts dramatically with a rate of 4.5 m/year measured over the preceding century for that volcano based on comparisons of photographs. These upward elevational shifts imply areal reductions for high‐elevation habitats, and particularly for the bunch grassland that is the focus of considerable local endemism. Abstract in Spanish is available with online material.
Daniel Jiménez‐García; Xingong Li; Andrés Lira‐Noriega; Andrew Townsend Peterson. Upward shifts in elevational limits of forest and grassland for Mexican volcanoes over three decades. Biotropica 2021, 53, 798 -807.
AMA StyleDaniel Jiménez‐García, Xingong Li, Andrés Lira‐Noriega, Andrew Townsend Peterson. Upward shifts in elevational limits of forest and grassland for Mexican volcanoes over three decades. Biotropica. 2021; 53 (3):798-807.
Chicago/Turabian StyleDaniel Jiménez‐García; Xingong Li; Andrés Lira‐Noriega; Andrew Townsend Peterson. 2021. "Upward shifts in elevational limits of forest and grassland for Mexican volcanoes over three decades." Biotropica 53, no. 3: 798-807.
Multi‐decadal inland surface water dynamics are of increasing interest due to their importance to climate, ecology, and society, yet several key challenges impede long‐term monitoring of inland surface waters globally. This research investigates two novel methods, one addressing sub‐hydroflattened surface estimate uncertainty issues, and a second addressing temporal resolution issues, using 46 water bodies across the western United States. First, low water level estimate uncertainty was reduced using multiple digital elevation models (ALOS, SRTM, and NED) to derive the hypsometric relationship for each lake from the digital elevation model with the lowest hydroflattened water surface. This technique reduced the number of images with sub‐hydroflattened water surfaces by at least 549 over the best individual DEM resulting in higher water surface elevation estimate accuracy. Second, this paper introduces proportional hypsometry which dynamically generates surface area/elevation relationships for every image using clear pixels only by removing contamination from both the image and DEM. Proportional hypsometry was found to be ill‐suited for sub‐hydroflattened water surface levels but produced comparable accuracy to clear images for above hydroflattened water levels. Overall, using the lowest hydroflattened surface along with proportional hypsometry improved temporal resolution enabling analysis of nearly 10,000 additional images while maintaining similar accuracy levels as images with <1% contamination (2.35 m RMSE vs 2.17 m RMSE). This research increases lower water elevation estimate accuracy and temporal resolution and is scalable enabling regional and global water dynamic analysis.This article is protected by copyright. All rights reserved.
David Weekley; Xingong Li. Tracking lake surface elevations with proportional hypsometric relationships, Landsat imagery, and multiple DEMs. Water Resources Research 2021, 57, 1 .
AMA StyleDavid Weekley, Xingong Li. Tracking lake surface elevations with proportional hypsometric relationships, Landsat imagery, and multiple DEMs. Water Resources Research. 2021; 57 (1):1.
Chicago/Turabian StyleDavid Weekley; Xingong Li. 2021. "Tracking lake surface elevations with proportional hypsometric relationships, Landsat imagery, and multiple DEMs." Water Resources Research 57, no. 1: 1.
Cost distance is one of the fundamental functions in geographical information systems (GISs). 3D cost distance function makes the analysis of movement in 3D frictions possible. In this paper, we propose an algorithm and efficient data structures to accurately calculate the cost distance in discrete 3D space. Specifically, Dijkstra’s algorithm is used to calculate the least cost between initial voxels and all the other voxels in 3D space. During the calculation, unnecessary bends along the travel path are constantly corrected to retain the accurate least cost. Our results show that the proposed algorithm can generate true Euclidean distance in homogeneous frictions and can provide more accurate least cost in heterogeneous frictions than that provided by several existing methods. Furthermore, the proposed data structures, i.e., a heap combined with a hash table, significantly improve the algorithm’s efficiency. The algorithm and data structures have been verified via several applications including planning the shortest drone delivery path in an urban environment, generating volumetric viewshed, and calculating the minimum hydraulic resistance.
Yaqian Chen; Jiangfeng She; Xingong Li; Shuhua Zhang; Junzhong Tan. Accurate and Efficient Calculation of Three-Dimensional Cost Distance. ISPRS International Journal of Geo-Information 2020, 9, 353 .
AMA StyleYaqian Chen, Jiangfeng She, Xingong Li, Shuhua Zhang, Junzhong Tan. Accurate and Efficient Calculation of Three-Dimensional Cost Distance. ISPRS International Journal of Geo-Information. 2020; 9 (6):353.
Chicago/Turabian StyleYaqian Chen; Jiangfeng She; Xingong Li; Shuhua Zhang; Junzhong Tan. 2020. "Accurate and Efficient Calculation of Three-Dimensional Cost Distance." ISPRS International Journal of Geo-Information 9, no. 6: 353.
Maintaining optimal ecological security is a serious issue in the Chinese Loess Plateau (CLP). Remote sensing ecological indexes (RSEI) of three main tableland regions of the CLP were calculated based on spectral information provided by remote sensing imaging satellites between 2000 and 2018. We were able to use RSEI values to systematically evaluate the temporal and spatial variation in the regional ecological environment and determine the influential factors that mainly associated with these changes. The results showed that between 2000 and 2018, the ecological environment improved, remained stable, and deteriorated, respectively, in the Gansu, Shaanxi, and Shanxi tablelands. Regions with poor or fair RSEIs were concentrated around the main river basins, while regions with moderate RSEIs were associated with poor ecological conditions and poor areas. The significant spatiotemporal variation in RSEI indicates that the ecological system in this region is relatively fragile. We also observed that natural factors such as the temperature, potential evapotranspiration, and precipitation had the greatest influence on the overall ecological quality. The rapid increase in the regional population and human activity played an important role in the variation in the regional RSEI. This research will provide important information on controlling regional soil erosion and ecological restoration in the CLP.
Congjian Sun; XiaoMing Li; Wenqiang Zhang; Xingong Li. Evolution of Ecological Security in the Tableland Region of the Chinese Loess Plateau Using a Remote-Sensing-Based Index. Sustainability 2020, 12, 3489 .
AMA StyleCongjian Sun, XiaoMing Li, Wenqiang Zhang, Xingong Li. Evolution of Ecological Security in the Tableland Region of the Chinese Loess Plateau Using a Remote-Sensing-Based Index. Sustainability. 2020; 12 (8):3489.
Chicago/Turabian StyleCongjian Sun; XiaoMing Li; Wenqiang Zhang; Xingong Li. 2020. "Evolution of Ecological Security in the Tableland Region of the Chinese Loess Plateau Using a Remote-Sensing-Based Index." Sustainability 12, no. 8: 3489.
Ecosystem water use efficiency (WUE) is a key indicator that depicts the carbon-water coupling relationship in terrestrial ecosystems. Separating the effects of climate change and human activities to the variation in WUE are essential for water resources and ecosystem management, especially for fragile ecosystems such as the Tibetan Plateau (TP). In this study, we introduced an analytical framework that combined the attribution approach with the elastic coefficient separation method to assess the impact of climate change and human activities on WUE variation in the TP from 1982 to 2015. The results are the following: (1) the multiyear mean annual WUE over the TP was 0.65 g C·kg−1 H2O and had a slightly increasing trend with a slope of 0.004 g C·kg−1 H2O yr−1 with about 87% of the vegetated area showed increasing trend. (2) WUE was positively correlated with temperature, precipitation and air pressure. The northwest TP tends to be a water-limited condition, while the thermal stress is spatially universal in the TP, climate warming and wetting promoted the gross primary productivity (GPP) and WUE enhancement in the TP. (3) WUE was more sensitive to GPP, and variation in WUE was mainly contributed by GPP. Climate change and human activities tend to cause more variations in GPP rather than evapotranspiration (ET), but great differences exist for different regions and vegetation types. (4) There was a good consistency between the WUE variation calculated by the framework and the actual WUE variation (R2 = 0.95). Climate change dominated the increase of WUE in the TP with a contribution rate of 79.8%, while human activities tend to reduce WUE (−20.2%). Ecological projects played a positive role in the ecological restoration of the TP, but there may be other human activities, which caused ecological degradation, that may need more attention in future ecological protections.
Liuming Wang; Mengyao Li; Junxiao Wang; Xingong Li; Lachun Wang. An analytical reductionist framework to separate the effects of climate change and human activities on variation in water use efficiency. Science of The Total Environment 2020, 727, 138306 .
AMA StyleLiuming Wang, Mengyao Li, Junxiao Wang, Xingong Li, Lachun Wang. An analytical reductionist framework to separate the effects of climate change and human activities on variation in water use efficiency. Science of The Total Environment. 2020; 727 ():138306.
Chicago/Turabian StyleLiuming Wang; Mengyao Li; Junxiao Wang; Xingong Li; Lachun Wang. 2020. "An analytical reductionist framework to separate the effects of climate change and human activities on variation in water use efficiency." Science of The Total Environment 727, no. : 138306.
Water resource management is of critical importance due to its close relationship with nearly every industry, field, and lifeform on this planet. The success of future water management will rely upon having detailed data of current and historic water dynamics. This research leverages Google Earth Engine and uses Landsat 5 imagery in conjunction with bathymetry and Shuttle Radar Topography Mission digital elevation model data to analyze long‐term lake dynamics (water surface elevation, surface area, volume, volume change, and frequency) for Lake McConaughy in Nebraska, USA. Water surface elevation was estimated by extracting elevation values from underlying bathymetry and digital elevations models using 5,994 different combinations of water indices, water boundaries, and statistics for 100 time periods spanning 1985‐2009. Surface elevation calculations were as accurate as 0.768 meters RMSE (CI95% [0.657, 0.885]). Water volume change calculations found a maximum change of 1.568 km3 and a minimum total volume of only 23.97% of the maximum reservoir volume. Seasonal and long‐term trends were identified which have major affects regarding regional agriculture, local recreation, and lake water quality. This research fills an existing gap in optical remote sensing‐based monitoring of lakes and reservoirs, is more robust and outperforms other commonly used monitoring techniques, increases the number of water bodies available for long‐term studies, introduces a scale‐able framework deployable within Google Earth Engine, and will enable data collection of both gauged and un‐gauged water bodies which will substantially increase our knowledge and understanding of these critical ecosystems.
David Weekley; Xingong Li. Tracking Multidecadal Lake Water Dynamics with Landsat Imagery and Topography/Bathymetry. Water Resources Research 2019, 55, 8350 -8367.
AMA StyleDavid Weekley, Xingong Li. Tracking Multidecadal Lake Water Dynamics with Landsat Imagery and Topography/Bathymetry. Water Resources Research. 2019; 55 (11):8350-8367.
Chicago/Turabian StyleDavid Weekley; Xingong Li. 2019. "Tracking Multidecadal Lake Water Dynamics with Landsat Imagery and Topography/Bathymetry." Water Resources Research 55, no. 11: 8350-8367.
In mountainous regions, solar radiation exhibits a strong spatial heterogeneity due to terrain shading effects. Terrain shading algorithms based on digital elevation models can be categorized into two types: area‐based and point‐specific. In this article, we evaluated two shading algorithms using designed mathematic surfaces. Theoretical shading effects over four Gauss synthetic surfaces were calculated and used to evaluate the terrain shading algorithms. We evaluated the area‐based terrain shading algorithm, Hillshade tool of ArcGIS, and the point‐specific shading algorithm from Solar Analyst (SA) in ArcGIS. Both algorithms showed shading overestimation, and Hillshade showed more accuracy with a mean absolute error (MAE) of 1.20%, as compared to the MAE of 1.66% of SA. The MAE of Hillshade increases exponentially as the spatial extent of the study area increases because the solar position for all locations on the surface is the same in Hillshade. Consequently, we suggest that the surface should be divided into more tiles in Hillshade when the discrepancy in the latitude of the whole surface is greater than 4°. Skyshed, which represents the horizon angle distribution in SA, is error‐prone over more complex terrain because horizon angle interpolation is problematic for such areas. We also propose a new terrain shading algorithm, with solar positions calculated using local latitude for each cell and the horizon angle calculated for every specific time interval, but without projections. The new model performs better than Hillshade and SA with an MAE of 0.55%.
Shuhua Zhang; Xingong Li; Jiangfeng She. Error assessment of grid‐based terrain shading algorithms for solar radiation modeling over complex terrain. Transactions in GIS 2019, 24, 230 -252.
AMA StyleShuhua Zhang, Xingong Li, Jiangfeng She. Error assessment of grid‐based terrain shading algorithms for solar radiation modeling over complex terrain. Transactions in GIS. 2019; 24 (1):230-252.
Chicago/Turabian StyleShuhua Zhang; Xingong Li; Jiangfeng She. 2019. "Error assessment of grid‐based terrain shading algorithms for solar radiation modeling over complex terrain." Transactions in GIS 24, no. 1: 230-252.
Solar radiation is the ultimate energy resource of earth surface energy balance and the main driving force of atmospheric, ecological and hydrological processes. Solar radiation over complex terrain has large spatial and temporal variation because of terrain shading and high cloud heterogeneity. While most existing GIS-based solar radiation models only work under clear sky condition, this research presents a solar radiation model which considers both terrain shading and anisotropic cloud attenuation and diffuse radiation using MODIS atmospheric products. Specifically, we use skyshed map, sky cloud maps, and sky weight map to represent angular distribution of sky obstruction, anisotropic cloud properties, and diffuse radiance over hemispherical sky, respectively. Combining skyshed map, sky weight map and sky cloud maps, we develop a solar radiation model where 3D geometrical relationships among sun, cloud, and terrain are considered and anisotropic diffuse radiance and cloud attenuation are modeled. Model results are evaluated using field observations in the Kunlun Mountains of western China. At Terra and Aqua overpass time, our model performs well with a mean relative bias (MRB) of −0.2%. It underestimates in clear and partly cloudy sky with a MRB of −5.86% and −4.79% and has a mean absolute relative bias (MARB) of 8.11% and 21.59% respectively. It overestimates under overcast sky with a MRB of 1.68% and has a MARB of 31.71%. Our model performs better when compared with existing instantaneous solar radiation products. For daily solar radiation, our model shows good performance with a MRB of 1.43% and MARB of 17.02%. Our model shows significant spatial variation of solar radiation within the study area with the influences from terrain and cloud. Our research provides a novel and improved approach to assimilating remote sensing data into GIS-based solar radiation modeling in mountainous terrain where observations are sparse and difficult to obtain.
Shuhua Zhang; Xingong Li; Jiangfeng She; Xiaomin Peng. Assimilating remote sensing data into GIS-based all sky solar radiation modeling for mountain terrain. Remote Sensing of Environment 2019, 231, 111239 .
AMA StyleShuhua Zhang, Xingong Li, Jiangfeng She, Xiaomin Peng. Assimilating remote sensing data into GIS-based all sky solar radiation modeling for mountain terrain. Remote Sensing of Environment. 2019; 231 ():111239.
Chicago/Turabian StyleShuhua Zhang; Xingong Li; Jiangfeng She; Xiaomin Peng. 2019. "Assimilating remote sensing data into GIS-based all sky solar radiation modeling for mountain terrain." Remote Sensing of Environment 231, no. : 111239.
The rapid increase in movement trajectory data causes data storage, transmission, computational processing, and visualization problems. These issues can be alleviated through trajectory simplification, which removes unnecessary details from raw trajectories. Most existing studies that focused on trajectory simplification considered freely moving objects, and they attempted to minimize position errors in their simplified representations in a two-dimensional plane. However, a large number of objects move within the constraint of road networks. In such constrained trajectory simplification, position error should be measured in the network space. Moreover, constrained trajectories contain a wealth of speed-change information that reflects the movement patterns of moving objects. In this study, we designed a data model, proposed error measurements, and developed a two-component method to simplify constrained trajectories. The geometric component in our method extended the classic Douglas–Peucker method using network distance to simplify trajectories with a guaranteed position error bound in network space. The semantic component enhanced the simplified representation by employing a data-enrichment strategy that allows users to control speed loss. Real trajectory data were used to assess the effectiveness of the proposed method. Experimental results show that our method has a lower position error than existing algorithms do when road network constrained trajectory data are simplified. The method can also preserve original speed in the simplified representation with a relatively low increase in data size. Our study thus provides an approach to simplifying trajectory data that guarantees error bounds in both location and speed.
Min Yang; Xiongfeng Yan; Xiang Zhang; Xingong Li. Constrained trajectory simplification with speed preservation. Cartography and Geographic Information Science 2019, 47, 110 -124.
AMA StyleMin Yang, Xiongfeng Yan, Xiang Zhang, Xingong Li. Constrained trajectory simplification with speed preservation. Cartography and Geographic Information Science. 2019; 47 (2):110-124.
Chicago/Turabian StyleMin Yang; Xiongfeng Yan; Xiang Zhang; Xingong Li. 2019. "Constrained trajectory simplification with speed preservation." Cartography and Geographic Information Science 47, no. 2: 110-124.
Lake ice is a robust indicator of climate change. The availability of information contained in Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow products from 2000 to 2017 could be greatly improved after cloud removal by gap filling. Thresholds based on open water pixel numbers are used to extract the freeze‐up start and break‐up end dates for 58 lakes on the Tibetan Plateau (TP), 18 lakes are also selected to extract the freeze‐up end and break‐up start dates. The lake ice durations are further calculated based on freeze‐up and break‐up dates. Lakes on the TP begin to freeze‐up in late October and all the lakes start the ice cover period in mid‐January of the following year. In late March, some lakes begin to break‐up, and all the lakes end the ice cover period in early July. Generally, the lakes in the northern Inner‐TP have earlier freeze‐up dates and later break‐up dates (i.e. longer ice cover durations) than those in the southern Inner‐TP. Over 17 years, the mean ice cover duration of 58 lakes is 157.78 days, 18 (31%) lakes have a mean extending rate of 1.11 d yr‐1 and 40 (69%) lakes have a mean shortening rate of 0.80 d yr‐1. Geographical location and climate conditions determine the spatial heterogeneity of the lake ice phenology, especially the ones of break‐up dates, while the physico‐chemical characteristics mainly affect the freeze‐up dates of the lake ice in this study. Ice cover duration is affected by both climatic and lake specific physico‐chemical factors, which can reflect the climatic and environmental change for lakes on the TP.
Yu Cai; Chang‐Qing Ke; Xingong Li; Guoqing Zhang; Zheng Duan; Hoonyol Lee. Variations of Lake Ice Phenology on the Tibetan Plateau From 2001 to 2017 Based on MODIS Data. Journal of Geophysical Research: Atmospheres 2019, 124, 825 -843.
AMA StyleYu Cai, Chang‐Qing Ke, Xingong Li, Guoqing Zhang, Zheng Duan, Hoonyol Lee. Variations of Lake Ice Phenology on the Tibetan Plateau From 2001 to 2017 Based on MODIS Data. Journal of Geophysical Research: Atmospheres. 2019; 124 (2):825-843.
Chicago/Turabian StyleYu Cai; Chang‐Qing Ke; Xingong Li; Guoqing Zhang; Zheng Duan; Hoonyol Lee. 2019. "Variations of Lake Ice Phenology on the Tibetan Plateau From 2001 to 2017 Based on MODIS Data." Journal of Geophysical Research: Atmospheres 124, no. 2: 825-843.
The accuracy of the standard Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow cover products (Collection 5) and several of the most common and computationally frugal gap-filling methods were validated using 12 years of daily observations from over 800 Snow Telemetry (SNOTEL) stations. While several factors affect snow cover accuracy to some extent, the largest controls are associated with land cover type; accuracy fell from the maximum in croplands (94.9%) to the minimum for observations with a land cover type of water (79.5%). The second largest impact on accuracy is attributed to the changes in solar zenith angle, where accuracy decreased from a maximum of ∼96% at 42° to a minimum of ∼84% at 58°. Based on the results of this work, the highest accuracy binary daily snow cover dataset can be achieved by reclassifying the fractional snow band using a no-snow/snow threshold of 10 from the MODIS Terra sensor. Gap-filling is best accomplished by a temporal filter on the same dataset, and the window length depends on the desired completeness of the final dataset and the amount of missing values in the area of interest. Decreases in accuracy caused by this gap-filling method taper off after 7 days. Therefore, if a larger temporal window is needed to adequately fill in a time series it is best to extend the window to the largest gap present.
James Coll; Xingong Li. Comprehensive accuracy assessment of MODIS daily snow cover products and gap filling methods. ISPRS Journal of Photogrammetry and Remote Sensing 2018, 144, 435 -452.
AMA StyleJames Coll, Xingong Li. Comprehensive accuracy assessment of MODIS daily snow cover products and gap filling methods. ISPRS Journal of Photogrammetry and Remote Sensing. 2018; 144 ():435-452.
Chicago/Turabian StyleJames Coll; Xingong Li. 2018. "Comprehensive accuracy assessment of MODIS daily snow cover products and gap filling methods." ISPRS Journal of Photogrammetry and Remote Sensing 144, no. : 435-452.
This research proposed a parallelized approach to scaling up the calculation of inundation height, the minimum sea‐level rise required to inundate a cell on a digital elevation model, which is based on Dijkstra's algorithm for shortest‐path calculations on a graph. Our approach is based on the concepts of spatial decomposition, calculate‐and‐correct, and a master/worker parallelization paradigm. The approach was tested using the U.S. Coastal Relief Model (CRM) dataset from the National Geophysical Data Center on a multicore desktop computer and various supercomputing resources through the U.S. Extreme Science and Engineering Discovery Environment (XSEDE) program. Our parallel implementation not only enables computations that were larger than previously possible, but also significantly outperforms serial implementations with respect to running time and memory footprint as the number of processing cores increases. The efficiency of the scalability seemed to be tied to tile size and flattened out at a certain number of workers.
C. J. Grady; Xingong Li. A distributed approach for calculating inundation height based on Dijkstra's algorithm. Transactions in GIS 2018, 22, 737 -759.
AMA StyleC. J. Grady, Xingong Li. A distributed approach for calculating inundation height based on Dijkstra's algorithm. Transactions in GIS. 2018; 22 (3):737-759.
Chicago/Turabian StyleC. J. Grady; Xingong Li. 2018. "A distributed approach for calculating inundation height based on Dijkstra's algorithm." Transactions in GIS 22, no. 3: 737-759.
We study the problem of morphing two polygons of building footprints at two different scales. This problem frequently occurs during the continuous zooming of interactive maps. The ground plan of a building footprint on a map has orthogonal characteristics, but traditional morphing methods cannot preserve these geographic characteristics at intermediate scales. We attempt to address this issue by presenting a turning angle function-based morphing model (TAFBM) that can generate polygons at an intermediate scale with an identical turning angle for each side. Thus, the orthogonal characteristics can be preserved during the entire interpolation. A case study demonstrates that the model yields good results when applied to data from a building map at various scales. During the continuous generalization, the orthogonal characteristics and their relationships with the spatial direction and topology are well preserved.
Jingzhong Li; Xingong Li; Tian Xie. Morphing of Building Footprints Using a Turning Angle Function. ISPRS International Journal of Geo-Information 2017, 6, 173 .
AMA StyleJingzhong Li, Xingong Li, Tian Xie. Morphing of Building Footprints Using a Turning Angle Function. ISPRS International Journal of Geo-Information. 2017; 6 (6):173.
Chicago/Turabian StyleJingzhong Li; Xingong Li; Tian Xie. 2017. "Morphing of Building Footprints Using a Turning Angle Function." ISPRS International Journal of Geo-Information 6, no. 6: 173.
Climate change and runoff response were assessed for the Tizinafu River basin in the western Kunlun Mountains, China, based on isotope analysis. We examined climate change in the past 50 years using meteorological data from 1957 to 2010. Results of the Mann-Kendall non-parametric technique test indicated that temperature in the entire basin and precipitation in the mountains exhibited significant increasing trends. Climate change also led to significant increasing trends in autumn and winter runoff but not in spring runoff. By using 122 isotope samples, we investigated the variations of isotopes in different water sources and analysed the contributions of different water sources based on isotope hydrograph separation. The results show that meltwater, groundwater and rainfall contribute 17%, 40% and 43% of the annual streamflow, respectively. Isotope analysis was also used to explain the difference in seasonal runoff responses to climate change. As the Tizinafu is a precipitation-dependent river, future climate change in precipitation is a major concern for water resource management.
Congjian Sun; Xingong Li; Wei Chen; Yaning Chen. Climate change and runoff response based on isotope analysis in an arid mountain watershed of the western Kunlun Mountains. Hydrological Sciences Journal 2016, 62, 319 -330.
AMA StyleCongjian Sun, Xingong Li, Wei Chen, Yaning Chen. Climate change and runoff response based on isotope analysis in an arid mountain watershed of the western Kunlun Mountains. Hydrological Sciences Journal. 2016; 62 (2):319-330.
Chicago/Turabian StyleCongjian Sun; Xingong Li; Wei Chen; Yaning Chen. 2016. "Climate change and runoff response based on isotope analysis in an arid mountain watershed of the western Kunlun Mountains." Hydrological Sciences Journal 62, no. 2: 319-330.
Snow in the mountainous watersheds of the Tarim River Basin is the primary source of water for western China. The Snow Cover Daily L3 Global 500-m Grid (MOD10A1) remote sensing dataset has proven extremely valuable for monitoring the changing snow cover patterns over large spatial areas; however, inherent uncertainty associated with large sensor zenith angles (SZAs) has called its reliability into question. Comparative analysis that utilized a paired-date difference method for parameters such as snow cover frequency, snow cover percentage, and normalized difference snow index (NDSI) has shown that overestimation of snow cover in the Tarim River Basin correlates with high values of SZA. Hence, such overestimation was associated with an increase in the NDSI, attributable to the change in reflectance between Band 4 and Band 6 imagery. A maximum threshold value of SZA of 22.37° was used alongside a multiday refilling method to modify the MOD10A1 dataset to produce a new daily snow cover map of the Tarim River Basin, spanning a 10-year period. A comparison of benchmark results of snow cover classification produced by the HJ-1A/B satellite revealed an increase in the overall accuracy of up to 4%, confirming the usefulness of our modified MOD10A1 data.
Haixing Li; Xingong Li; Pengfeng Xiao. Impact of Sensor Zenith Angle on MOD10A1 Data Reliability and Modification of Snow Cover Data for the Tarim River Basin. Remote Sensing 2016, 8, 750 .
AMA StyleHaixing Li, Xingong Li, Pengfeng Xiao. Impact of Sensor Zenith Angle on MOD10A1 Data Reliability and Modification of Snow Cover Data for the Tarim River Basin. Remote Sensing. 2016; 8 (9):750.
Chicago/Turabian StyleHaixing Li; Xingong Li; Pengfeng Xiao. 2016. "Impact of Sensor Zenith Angle on MOD10A1 Data Reliability and Modification of Snow Cover Data for the Tarim River Basin." Remote Sensing 8, no. 9: 750.
Weather monitoring systems, such as Doppler radars, collect a high volume of measurements with fine spatial and temporal resolutions that provide opportunities to study many convective weather events. This study examines the spatial and temporal characteristics of severe thunderstorm life cycles in central United States mainly covering Kansas, Oklahoma, and northern Texas during the warm seasons from 2010 to 2014. Thunderstorms are identified using radar reflectivity and cloud-to-ground lightning data and are tracked using a directed graph model that can represent the whole life cycle of a thunderstorm. Thunderstorms were stored in a GIS database with a number of additional thunderstorm attributes. Spatial and temporal characteristics of the thunderstorms were analyzed, including the yearly total number of thunderstorms, their monthly distribution, durations, initiation time, termination time, movement speed and direction, and the spatial distributions of thunderstorm tracks, initiations, and terminations. Results revealed that thunderstorms were most frequent across the eastern part of the study area, especially at the borders between Kansas, Missouri, Oklahoma, and Arkansas. Finally, thunderstorm occurrence is linked to land cover, including a comparison of thunderstorms between urban and surrounding rural areas. Results demonstrated that thunderstorms would favor forests and urban areas. This study demonstrates that advanced GIS representations and analyses for spatiotemporal events provide effective research tools to meteorological studies.
Weibo Liu; Xingong Li. Life Cycle Characteristics of Warm-Season Severe Thunderstorms in Central United States from 2010 to 2014. Climate 2016, 4, 45 .
AMA StyleWeibo Liu, Xingong Li. Life Cycle Characteristics of Warm-Season Severe Thunderstorms in Central United States from 2010 to 2014. Climate. 2016; 4 (3):45.
Chicago/Turabian StyleWeibo Liu; Xingong Li. 2016. "Life Cycle Characteristics of Warm-Season Severe Thunderstorms in Central United States from 2010 to 2014." Climate 4, no. 3: 45.
The Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas has collected approximately 1000 terabytes (TB) of radar depth sounding data over the Arctic and Antarctic ice sheets since 1993 in an effort to map the thickness of the ice sheets and ultimately understand the impacts of climate change and sea level rise. In addition to data collection, the storage, management, and public distribution of the dataset are also primary roles of the CReSIS. The Open Polar Server (OPS) project developed a free and open source infrastructure to store, manage, analyze, and distribute the data collected by CReSIS in an effort to replace its current data storage and distribution approach. The OPS infrastructure includes a spatial database management system (DBMS), map and web server, JavaScript geoportal, and MATLAB application programming interface (API) for the inclusion of data created by the cryosphere community. Open source software including GeoServer, PostgreSQL, PostGIS, OpenLayers, ExtJS, GeoEXT and others are used to build a system that modernizes the CReSIS data distribution for the entire cryosphere community and creates a flexible platform for future development. Usability analysis demonstrates the OPS infrastructure provides an improved end user experience. In addition, interpolating glacier topography is provided as an application example of the system.
Weibo Liu; Kyle Purdon; Trey Stafford; John Paden; Xingong Li. Open Polar Server (OPS)—An Open Source Infrastructure for the Cryosphere Community. ISPRS International Journal of Geo-Information 2016, 5, 32 .
AMA StyleWeibo Liu, Kyle Purdon, Trey Stafford, John Paden, Xingong Li. Open Polar Server (OPS)—An Open Source Infrastructure for the Cryosphere Community. ISPRS International Journal of Geo-Information. 2016; 5 (3):32.
Chicago/Turabian StyleWeibo Liu; Kyle Purdon; Trey Stafford; John Paden; Xingong Li. 2016. "Open Polar Server (OPS)—An Open Source Infrastructure for the Cryosphere Community." ISPRS International Journal of Geo-Information 5, no. 3: 32.
By using 233 isotope samples, we investigated the spatial and temporal variations of δ18O and δ2H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ18O and δ2H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ18O and δ2H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary.
Congjian Sun; Xingong Li; Yaning Chen; Weihong Li; Randy L. Stotler; Yongqing Zhang. Spatial and temporal characteristics of stable isotopes in the Tarim River Basin. Isotopes in Environmental and Health Studies 2016, 52, 281 -297.
AMA StyleCongjian Sun, Xingong Li, Yaning Chen, Weihong Li, Randy L. Stotler, Yongqing Zhang. Spatial and temporal characteristics of stable isotopes in the Tarim River Basin. Isotopes in Environmental and Health Studies. 2016; 52 (3):281-297.
Chicago/Turabian StyleCongjian Sun; Xingong Li; Yaning Chen; Weihong Li; Randy L. Stotler; Yongqing Zhang. 2016. "Spatial and temporal characteristics of stable isotopes in the Tarim River Basin." Isotopes in Environmental and Health Studies 52, no. 3: 281-297.
This research assessed two grid-based direct solar radiation models, ESRI’s Solar Analyst (SA) and Kumar’s model (KM), using artificial surfaces. Mathematically derived radiation on the surfaces was compared with grid-based model results. While both models showed good consistency with theoretical derivations, they both underestimated direct radiation at daily, most seasonal, and annual scales. KM performed better than SA at all the scales except at annual scale and in the summer. Horizon angle calculation and numerical integration are the common error sources in both models. Interpolation in horizontal angles and the use of a sky size parameter are the additional error sources in SA. Larger errors were found in SA when the sky size parameter and modeling time interval were not compatible. Overall, KM is a better choice for direct solar radiation modeling as it is more accurate and computationally efficient, easier to understand, and needs fewer parameters.
Shuhua Zhang; Xingong Li; Yaning Chen. Error assessment of grid-based direct solar radiation models. International Journal of Geographical Information Science 2015, 29, 1782 -1806.
AMA StyleShuhua Zhang, Xingong Li, Yaning Chen. Error assessment of grid-based direct solar radiation models. International Journal of Geographical Information Science. 2015; 29 (10):1782-1806.
Chicago/Turabian StyleShuhua Zhang; Xingong Li; Yaning Chen. 2015. "Error assessment of grid-based direct solar radiation models." International Journal of Geographical Information Science 29, no. 10: 1782-1806.