How accurate are GPS on iPhone 4?

Question

quick question. How accurate are GPS on iPhone 4? I ask because I am working on a corporate project for the company, and part 2 will be devoted to the development of iDevice, where I must determine the position of the user. I would like to know if the GPS is accurate enough to perceive the user moving in the rooms, because the user will have to “mark” sections of the room when they move around it.

Thanks in advance!

PS If we assume that this will not matter much, but users will actually find themselves using an iPad, not an iPhone, and most likely, iPad 2 will be absent by the time the entire project is completed. I don’t know if iPad 2 is better than a GPS receiver or not, but at least I have to use an iPad / iPhone 4 GPS receiver ...

Answer 1

Most buildings will not allow you to get an accurate set of GPS signals (if they can be received at all) indoors. The roof / ceiling / ceiling on top is too thick. Even a lot of trees hanging over the building will degrade the signal from GPS satellites.

You may have a chance if all rooms have very large unobstructed windows without protrusions, and this is the right time of day for several satellites to see this window.

Outdoors, in a clear view, the iPhone 4 GPS seems very accurate. Sometimes I can walk around a parked car and see a blue dot in the Maps application, following me in circles.

Answer 2

I have done some work with a large dataset. My result set is based on cars driving outside, and therefore will be on average more accurate than those made inside (based on line of sight for satellites).

For the 650 704 location updates that I used in my tests, I found that the average accuracy radius was 246 m (91 m if you delete> 1 km of ejection). 85.1% of updates had an accuracy of less than 100 m. Therefore, given that your update will not be as accurate as this, I do not think that you will have many successful tracking changes in the room.

A further description of my results .

Answer 3

This is very difficult, and most of the time it is not possible to receive a GPS signal inside the building. The type of waves used by GPS (radio waves) is not effective enough to go through the structure itself.

A simpler and probably cheaper solution would be to give people perhaps tags or cards and install some trnasreceiver in each issue.

Answer 4

The initial question seems to be: “How accurate is the GPS on the iPhone 4,” which I haven't answered yet.

I tested a lot with accuracy to GPS chips in iPhone 4, iPhone 4 and iPhone 5, and the most accurate reading seemed ~ 5 meters or ~ 16 feet when you are out with a clear field of view to the sky. I assume this is a software limitation imposed by Apple to save battery.