| 词条 | Ionospheric pierce point |
| 释义 |
Most global navigation satellite systems (GNSS) are subjected to errors induced by the ionosphere. Because ionospheric delay affects the speed of microwave signals differently depending on their frequency—a characteristic known as dispersion, delays measured on two or more frequency bands can be used to measure dispersion, and this measurement can then be used to estimate the delay at each frequency. The principal source of the dispersion comes from the total electron content (TEC) in the ionosphere, along the line of sight from the satellite to the receiver. Because it is difficult to measure the TEC along the line of sight, instead a prediction can be made using a simplified model of the ionosphere. This model assumes that the ionosphere is a thin, uniform-density shell about the earth, located near the mean altitude H of maximum TEC (approx. 350 km). Using geometry, a slant intersection with this shell model can be determined and a vertical TEC measurement inferred. The intersection between line of sight and this shell is called the ionospheric pierce point (IPP). The perpendicular projection onto the earth's surface is called the subionospheric point. ReferencesSources
External links
2 : Global Positioning System|Ionosphere |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。