Question for users in Victoria, Australia

[irvandriel]

This is a question to people who have used Laptimer with a TomTom GPS on tracks around Melbourne, Australia
I am using laptimer with a TomTom GPS and iPhone 3G. I have found the setup works pretty well at Sandown but GPS reception at Phillip Island and Winton is quite poor and I don't get any useful lap times. GPS Reception at PI and Winton is sometimes green bu often drops to yellow or red.
I'm wondering if my TomTom is working properly. Does anyone else have this problem? I know other people with dedicated GPS timers have no problems.
Thanks
Ian