Bernie asks "can someone please explain why the week changes the position?" It doesn't change the postion, just the way the calculations on the receiver work out. GPS uses a time differential of multiple satellites to determine position. So the date-time info transmitted by the satellite to the GPS receiver is integral in calculating your position. If the firmaware can't 'digest' the data being received, it ends up behaving in an undesired way. The coastguard had a site on this - but I can't get it to open - the spec is there. But, a tutorial on GPS is available at http://www.trimble.com/gps/howworks/aa_hw1.htm You might also try http://www.howstuffworks.com/gps.htm This is a microcosm of the whole Y2K software problem. When you write a human interface you sometimes spend as much effort on programming for users who make "wrong" inputs as you do for the valid ones - trying to make the software "idiot proof." A simple example: Valid inputs are "Y" or "N" but you know somebody's going to press <Enter> or maybe "?" - and you have to determine what behaviors you want when that happens. When hardware communicates directly with hardware things can be greatly simplified if everybody conforms to a standard. You don't have to worry so much about unpredicted responses. Just determine what to do with the allowed data and then what is the default behavior when a disallowed data is received. In the GPS system, the data itself is OK, but the firmware may not recognize it as such. In other cases, the data may be completely unrelated to the date, but the date is in a header. And if the header format is violated, the whole data set may be taken as invalid. So what happens when an error condition exists? Does the system request a repeat? Nice if it can. Does it send up a flag and shut down? Not too bad. Does it "do the best it can" with lousy data? That could cause an unknown or hard to trace error to propagate through the system. Does it cut off a piece of equipment or a power line to avoid damage? I suspect that some controllers in power grids work this way. So, even equipment that has NOTHING to do with the date, may be impacted by the fact that the date is not understandable on one or the other side of a "conversation." With that, I'll sign off on this topic...Bye! Bob To unsubscribe from SURVPC send a message to [EMAIL PROTECTED] with unsubscribe SURVPC in the body of the message. Also, trim this footer from any quoted replies.
