Disable "cellphone" to save battery

view story

http://androidforums.com – Hi I'm having a Sony X8 with Android 2.1. I use it to track my bicycle rides, so the GPS is essential. But I don't need the phone-part of the phone when riding. I hope you understand me, I don't want to talk to anybody on the phone anyway, do I usually mute the phone. Is it possible to turn the "cell phone-feature" off and still be able to use the GPS? I tried airplane mode, but the GPS seems to be too inaccurate when in airplane mode. (General)