A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effecti...A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.展开更多
针对全球数值模式在复杂地形区域强降水落区和强度预报上存在的短板,本研究选取了区域模式降水预报地形订正法,通过消空和海拔高度重置等试验,应用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF,简称...针对全球数值模式在复杂地形区域强降水落区和强度预报上存在的短板,本研究选取了区域模式降水预报地形订正法,通过消空和海拔高度重置等试验,应用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF,简称EC)模式的地形数据及每日08:00(北京时)起报的逐3 h风、降水量及相对湿度等气象要素,定量估算地形作用所导致的降水增减量,形成改善后的全球模式降水预报地形订正法。为验证该方法的有效性,对2021—2022年汛期(6—8月)川西高原东坡过渡带的降水预报进行了订正,并开展了逐日降水检验评估和31次强降水检验评估。结果表明,经过地形订正后的各量级降水TS(threat score)评分较EC模式预报均有显著提升31次强降水检验评估中,大雨、暴雨和大暴雨量级的评分分别提高了11%、126%和267%。同时,预报的命中率也得到显著提高,大雨、暴雨和大暴雨的命中率分别达到了45.5%、20%和8%,而漏报率分别减少至54.5%、80%和92%。此外,大雨、大暴雨的空报率也分别降低至50.5%和84.5%。偏差评分值更接近于1,进一步证明了该地形订正方法的有效性。展开更多
Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of eleva...Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.展开更多
To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwat...To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation（LSE） is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.展开更多
文摘A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.
文摘针对全球数值模式在复杂地形区域强降水落区和强度预报上存在的短板,本研究选取了区域模式降水预报地形订正法,通过消空和海拔高度重置等试验,应用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF,简称EC)模式的地形数据及每日08:00(北京时)起报的逐3 h风、降水量及相对湿度等气象要素,定量估算地形作用所导致的降水增减量,形成改善后的全球模式降水预报地形订正法。为验证该方法的有效性,对2021—2022年汛期(6—8月)川西高原东坡过渡带的降水预报进行了订正,并开展了逐日降水检验评估和31次强降水检验评估。结果表明,经过地形订正后的各量级降水TS(threat score)评分较EC模式预报均有显著提升31次强降水检验评估中,大雨、暴雨和大暴雨量级的评分分别提高了11%、126%和267%。同时,预报的命中率也得到显著提高,大雨、暴雨和大暴雨的命中率分别达到了45.5%、20%和8%,而漏报率分别减少至54.5%、80%和92%。此外,大雨、大暴雨的空报率也分别降低至50.5%和84.5%。偏差评分值更接近于1,进一步证明了该地形订正方法的有效性。
基金Supported by the National Natural Science Foundation of China(61363075)the National High Technology Research and Development Program of China(863 Program)(2012AA12A308)the Yue Qi Young Scholars Program of China University of Mining&Technology,Beijing(800015Z1117)
文摘Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51179035 and 51279221)the Natural Science Foundation of Heilongjiang Province(Grant No.E201121)
文摘To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation（LSE） is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.
