Part of the problem with the accuracy may be the quality of GPS satellite coverage in your area.
GPS works by calculating your position based on timing how long it takes the signal to travel from GPS satellites to the receiver. The more satellites spread out through the sky, the better the calculation will be. If the satellites are grouped in one part of the sky at that time, the accuracy will suffer.
Some areas of the country have periods throughout the day where the satellite coverage is less than optimal. Combined with if a satellite in the GPS constellation goes down, that can pose problems as well.
I have found the iPhone GPS precision is good but not great. Sometimes it shows me on a frontage road when I am on an interstate but overall its not too bad.
I am actually using my iPhone GPS collect coordinates of devices I am responsible instead of borrowing a GPS unit from another office since I do not need centimeter accuracy of the location.
The ipad is insanely accurate.
I have done some tests. The ipad locks on much faster then the iPhone. I have to wait for the iphone to narrow down my position while the iPad instantly has a lock.
I tracked my position in a car park. The iPhone knew I was in the parking lot, the iPad knew which corner of which parking space I was in.
Also does anyone know does the A4 chip also include the GPS chip?
Thanks
I do a lot of geocaching and have both an iPhone 3GS and an iPad Wifi+3G. I use both when geocaching. Because it is dangerous to drive while navigating with the iPad I use the iPhone until the time comes to get out of the car and do some walking. I have found both to be accurate, but the iPad to be a bit more accurate. When you get close to the site with the iPhone the map begins to jiggle so much that it is hard to see it, while the iPad is steady as a rock. Also where the best accuracy I can get on the iPhone is within 9 to 12 feet of the site the iPad will get within one foot of the site while being extremely steady.