All iPhones have a built in GPS receiver. Only Wi-Fi+Cellular iPads have a built in GPS receiver. Wi-Fi only iPads do not have GPS receivers, but can still get limited position information from a Wi-Fi network.
If you have a GPS equipped device that is not getting good accuracy, please review the following items:
- Make sure your iPad or iPhone have a clear view of the sky. Putting your device in a side-pocket or other obscured location will decrease GPS accuracy.
- Some cases can interfere with your GPS reception. Try removing your case to see if that helps to improve accuracy.
- In some cases, electrically heated windshields have interfered with GPS accuracy. If possible, try turning the windshield heat off to see if there is a change to accuracy.
- Ensure the date, time, and timezone are correctly set on the device in Settings > General > Date & Time.
- Sometimes rebooting the iPad can fix a problem with location accuracy.
- The internal GPS is not WAAS and not "aviation" grade. While you can often get 5-10m accuracy fixes from it, it is not as reliable as an aviation handheld. Additionally there is a second or so lag in position updates compared to purpose-build aviation handhelds.
If you have a Wi-Fi only device, it is not uncommon for the position information to have a low degree of accuracy, to be intermittent, or to be devoid of any position information. This is because there is no GPS signal coming into the device. Instead, the Wi-Fi only device is relying on a Wi-Fi network to determine its position. This method of location determination can be accomplish by measuring signal intensity from an access point, utilizing location databases, or some other means. Position information accuracy via Wi-Fi can be highly variable from network to network.
If you have a Wi-Fi only iPad and want accurate GPS position information, then you will need to utilize an external GPS receiver. ForeFlight currently recommends the Bad Elf or the DUAL external GPS'. ADS-B receivers, such as the Stratus or Garmin GDL-39, not only provide ADS-B data, but also provide GPS position information.
Last, ForeFlight is able to receive available GPS position information from avionics systems that connect to ForeFlight through the ForeFlight Connect option. You can learn more about that here: