The new geoid model of Tanzania is a major breakthrough in the determination of vertical heights for the past 60 years. A new geoid model has been computed using precise gravity data supplemented with marine gravity d...The new geoid model of Tanzania is a major breakthrough in the determination of vertical heights for the past 60 years. A new geoid model has been computed using precise gravity data supplemented with marine gravity data from Gravity Recovery and Climate Experiment （GRACE） satellite and new high-resolution satellite gravity data from Gravity field and steady-state Ocean Circulation Explorer （GOCE）. A digital terrain model was also used based on 15＂ Shuttle and Rader Terrain Model （SRTM） data. The use of gravity data makes an orthometric height easily computed using Global Navigation Satellite System （GNSS）. The GNSS is being used in many African countries including Tanzania and soon it will replace conventional leveling technique and avoid frequent maintenance of benchmarks. This paper presents preliminary result of a new geoid model which shows that by using precious gravity data and Remove-Compute-Restore technique, an accuracy of 10 cm can be reached.展开更多
It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolutio...It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.展开更多
CHAMP satellite data and ground-based magnetic observations are used and combined to map the lithospheric magnetic field over China by means of the revised spherical cap harmonic analysis(R-SHCA)modeling technique.The...CHAMP satellite data and ground-based magnetic observations are used and combined to map the lithospheric magnetic field over China by means of the revised spherical cap harmonic analysis(R-SHCA)modeling technique.The magnetic field is described to a spatial resolution of 150 km at the mean Earth’s radius,which represents a good compromise between the resolutions afforded by surface and satellite data.We compare the magnetic anomalies modeled at the regional scale with composite regions containing large-scale of tectonic structures.These regions,including the Tarim Basin and the Tibetan Plateau,are correlated with regional magnetic anomalies at satellite altitude but contain a significant number of small-scale and complex magnetic structures at the mean Earth’s radius.These magnetic anomalies are globally consistent with the known geological features in China but also offer a way to delineate the contours of the geological blocks and to discuss the connection between magnetic anomalies and the heat flow distribution in this region.展开更多
文摘The new geoid model of Tanzania is a major breakthrough in the determination of vertical heights for the past 60 years. A new geoid model has been computed using precise gravity data supplemented with marine gravity data from Gravity Recovery and Climate Experiment （GRACE） satellite and new high-resolution satellite gravity data from Gravity field and steady-state Ocean Circulation Explorer （GOCE）. A digital terrain model was also used based on 15＂ Shuttle and Rader Terrain Model （SRTM） data. The use of gravity data makes an orthometric height easily computed using Global Navigation Satellite System （GNSS）. The GNSS is being used in many African countries including Tanzania and soon it will replace conventional leveling technique and avoid frequent maintenance of benchmarks. This paper presents preliminary result of a new geoid model which shows that by using precious gravity data and Remove-Compute-Restore technique, an accuracy of 10 cm can be reached.
基金supported by the Chinese Academy of Sciences Action Plan for West Development Project (Grant No. KZCX2-XB3-15)the National High-tech R&D Program of China (Grant No. 2012AA12A304)
文摘It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.
基金supported by National Natural Science Foundation of China(Grant Nos.4117412240890163&41031066)OPWSRP(Grant No.201005017)
文摘CHAMP satellite data and ground-based magnetic observations are used and combined to map the lithospheric magnetic field over China by means of the revised spherical cap harmonic analysis(R-SHCA)modeling technique.The magnetic field is described to a spatial resolution of 150 km at the mean Earth’s radius,which represents a good compromise between the resolutions afforded by surface and satellite data.We compare the magnetic anomalies modeled at the regional scale with composite regions containing large-scale of tectonic structures.These regions,including the Tarim Basin and the Tibetan Plateau,are correlated with regional magnetic anomalies at satellite altitude but contain a significant number of small-scale and complex magnetic structures at the mean Earth’s radius.These magnetic anomalies are globally consistent with the known geological features in China but also offer a way to delineate the contours of the geological blocks and to discuss the connection between magnetic anomalies and the heat flow distribution in this region.
