Ira wrote: >The GPS began giving really improbable >speed readings. It would drop to zero, then suddenly pick back up and go >to as much as 8 or 9 mph (not likely!) before fading back to more >realistic speeds. It also, at one point, swung the course indicator all >the way around to indicate I was moving west instead of east. I was just >wondering if I could find the manual to see about getting it serviced, >when it flashed a message telling me the batteries were about dead and >should be replaced. Hopefully, that will prove to be the reason for the >bizarre readings. > Hi Ira, Though it could well have been exacerbated by low batteries, the basic cause of your problem is the Selective Availability imposed by the US military. They deliberately scramble the signal to limit accuracy for civilian receivers. This error is varied second by second and causes the position where the GPS "thinks" it is to hopscotch in a band around your actual position. Your speed is computed as a rolling average of progress over the last minute or so, and at the slower speeds that paddlers typically move, your actual speed can be washed out by the apparent changes caused by the SA. Some GPSs allow you to increase the time over which your GPS averages speed (it would need to be 5 minutes or more to be really meaningful for kayaks, I think.) This may be possible to do either directly on the GPS unit itself - it would probably be under the "Preferences" or "Navigation Set-Up" menus, or through the PC software programs that are sold as after market accessories. Thanks for the report, and happy paddling. Philip T. **************************************** Mountain Equipment Co-op 1655 West 3rd Avenue, Vancouver, BC, Canada V6J 1K1 Tel: 640-732-1989 Fax: 604-731-6483 email: pid_at_mec.ca Visit our website at: http://www.mec.ca ***************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Tue Oct 27 1998 - 08:25:54 PST
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:30:00 PDT