Development of a data processing and distribution system for total electron content data of a GPS receiver network

利用地理勘测研究所运营的GPS接收器网络GeoNet的观测数据，开发了一个在日本境内推导和分发总电子含量(TEC)数据的系统。GeoNet在大约1000个接收器上每隔30秒从GPS卫星获取定位数据。考虑到视线和电离层之间的几何关系，将观测到的定位数据转换为垂直TEC。为了减少这种转换带来的误差，在这个过程中省略了低仰角的数据。利用这一GeoNet TEC数据，得到了日本上空TEC的二维分布，时间分辨率为30秒，经纬度为0.15度。得到的TEC的精度估计为2-4x10^&lt；16电子/m^2。用最小二乘法从观测的TEC数据中估计并减去发射器和接收器内部的电气偏置。自1999年4月以来的所有GeoNet数据…更多的人用这种方法处理，新获得的数据也每天都在处理。导出的技术经济数据存储在数据库中，并可通过万维网访问，网址为http://stegps.kugi.kyoto-u.ac.jp/.该数据库提供了四种类型的数据：ATEC(每个接收者的TEC绝对值)、TEC(每个接收者的包含偏差的TEC数据)、AGRJD(日本上空绝对TEC的二维分布)和GRID(摄动TEC的二维分布)。数据库中还存储了TEC的二维图。该数据库有交互式绘图页面，可以在任何给定的日期和位置绘制TEC的图表。利用该数据库，对中纬度电离层进行了若干研究。利用GeoNet的TEC数据探测到了中等尺度的行进电离层扰动，并与气辉成像仪和MU雷达等其他测量数据进行了比较。利用GeoNet TEC数据详细研究了地磁暴期间的电离层扰动。较少

A system to derive and distribute Total Electron Content (TEC) data over Japan was developed using the observational data of GEONET, a GPS receiver network operated by Geographical Survey Institute. GEONET obtains positioning data from GPS satellites in every 30 seconds at about 1000 receivers. The observed positioning data were converted to vertical TEC considering the geometry between the line-of-sight and the ionosphere. To reduce errors caused by this conversion, the data with low elevation angles were omitted in this process. Using this GEONET TEC data, two-dimensional distribution of TEC over Japan was derived with 30 seconds of temporal resolution and 0.15 degrees of spatial resolution in latitude and longitude. The accuracy of the derived TEC was estimated to be 2-4x10^<16> electron/m^2. Electrical biases inside of the transmitters and receivers were estimated and subtracted from the observed TEC data with the least-square fitting method. All of GEONET data since April in 1999 … More were processed with this method and newly obtained data are also processed every day. The derived TEC data are stored in a data base and can be accessed through WWW at http://stegps.kugi.kyoto-u.ac.jp/. Four types of data are provided in this data base : ATEC (absolute value of TEC for each receiver), TEC (TEC data for each receiver containing biases), AGRJD (two-dimensional distribution of absolute TEC over Japan) and GRID (two-dimensional distribution of perturbation TEC). Two-dimensional maps of TEC are also stored in the data base. The data base has interactive plot pages to make plots of TEC at any given dates and positions. Using this data base, several studies on the mid-latitude ionosphere were carried out. The medium-scale traveling ionospheric disturbances were detected by the GEONET TEC data and compared with the data by the other measurements, such as air-glow imagers and the MU radar. Ionospheric disturbances during the geomagnetic storm periods were studied in detail with GEONET TEC data. Less