Cellphones and IP address

On lineland phones when one calls 911 they know exacty where you are, but on cellphones the location maybe 30 to100 miles off.
For example you may be actually in Texas but the caller ID at the police station may display that you're in Mexico.

So when using cellphone for 911 let the dispatcher know exactly where you are and don't depend on the automatic location device.

On IP address when my connection gets disconnected and then connected again,

the computer says it is searching for an IP address. This too may be 30 to 100 miles off. I may be in Springfield, Illinois but the ip address may display I am in Chicago.

Now since sometimes my IP address changes does that mean no one can find me ? The answer is no. They would simply contact my ISP and they will say something like "Well, at 2 PM today he was at this IP address, the next day at 5 PM he was at this IP address.