询问专家：GPS信号跟踪

您是否曾经想过GPS信号跟踪功能“ L1P，L2E”？我们的一位读者向我们的专家询问了解释，这就是他回答的。

我们从我们的一位读者那里收到了以下问题：“在研究各种调查级产品的GNSS接收器规格时，我观察到其中一些列出了以下GPS信号跟踪功能：“ L1P，L2E”。我无法找到对这些特定信号频率的引用。它们是否在网上可用的各种信号规格中可能未列出的全新频率和/或它们可能只是“窗帘”，这确实与产品的信号跟踪和性能无关？”。我们将这个问题传递给了Huibert-Jan Lekkerkerk，该问题的编辑188金宝搏特邀Gim International'and an expert on GNSS and positioning, to solve the issue. This is his answer:

Without further details, this is a tricky question to answer. L1P usually refers to the P code transmitted on the L1 frequency (and the L2 frequency). This is a regular code that is reserved for military use. In the early days and especially during the Gulf War, the P code was plainly transmitted. Older and/or military-capable receivers may list this as a code which can be received. However, it cannot be used because the code as such is not transmitted anymore; it has been replaced by its encrypted version, the Y code. By the way,Glonass还具有L1和L2频率上具有相同功能的P代码。

The L2E code is a bit of a mystery. I assume it was found in the documentation for a slightly older receiver, perhaps dating from the early 2000s. In those days, the signal modernization plan for GPS had not yet been completed and different frequency designations were ‘created’ to indicate future possibilities. There is currently no L2E signal that I am aware of. However, the E could also refer to the ‘Enhanced L2C’ which functions essentially the same as the L2C code but is available on the GPS Block III satellites (which were probably only in the design stage when the specifications for the receivers you found were drawn up).

当时，对于某些营销部门而言，根据制造商而言，承诺在现实词导航中基本上毫无价值的信号并不罕见。一个例子是即使太空中唯一的卫星是giove-a和giove-b，伽利略的长期接收。伽利略的规格直到2010年才具有确定性，但是大多数接收器都可以根据营销部门完全使用它（并且只有在您检查小印刷品时，您才能看到：“有未来的固件更新……”）。通常，意味着接收器能够获得频率，但不能实际使用信号。

The full frequency/signal plan can be found in the Interface Control Documents (ICD) and Interface Specifications for GPS:https://www.gps.gov/technical/icwg/。如果不在ICD中，则不正式存在！在这种情况下，该文档确实列出了一组L2C代码，包括L2CM，L2CL和两个增强版本。从本质上讲，它们通常在接收器规格中被指定为L2C，因为它们构成了同一信号的一部分。