----- Original Message ----- From: "M Graff" To: "Microcontroller discussion list - Public." Sent: Thursday, December 08, 2005 11:19 PM Subject: Re: [PIC] DGPS | Enrico Schuerrer wrote: | > The L2 signal has as far as I know 2 encrypted parts - one part is for | > commercial purposes and you have to pay for the key, the other part is | > military. | | I doubt this is the case. The military is unlikely to share a data | stream with lowly commercial types when they clearly work so hard to | keep it military only. | | All the documents I can find refer to civilian (L1) and military (l2) | bands. There is no distinction made between general public and | commercial use. Even the FAA does not use the military signal, after all. | Now we have to go inside the signal... The known P-Code and the unknown W-Code will be combined to the new Y-code. This code can be decrypted by different keys - one with the result of a lower accuracy and one with the result of a higher accuracy. The latter is known as the military code, the former as the commercial one. There are even other methods of L2 tracking available which allows higher accuracy as the civilian signal, but not as accurate as the military code. I've learned this in a seminar for surveying combined with DGPS which allows an accuracy up to 10cm with long term measurements. Due to the fact that my documentation was a handout of the instructor I am afraid I can't name no reference weblinks. Enrico (and sorry for my English, I'm no native speaker) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist