Most of the time the signal can't go through things you can't see through; your vehicle's roof, trees, buildings. In a vehicle, the best place for the GPS will be under the front window where the GPS will get a clear view of the sky above. All smartphones come equipped with access to the internet via the cellular phone data network. These units also include "A-GPS". The "A" stands for "assisted", as in assisted by the cell towers. So if your smartphone (with cellular) has a connection to the cell towers, the assisted GPS inside your smartphone will work well enough for most activities. But away from the cell towers, up in the sky, out in the woods, or at sea, the GPS can take 20 minutes or more to initially locate you.
These can not only block the signals, but can give you reflected signals, which will degrade the accuracy of the data.
These can interfere with the signal, so if possible try staying away from those objects. Keep your battery charged. Not only does this give your GPS better performance it will also help keep a better signal.
Some pouches may reduce the GPS signal quality, especially if it has a magnetic clip. Set up your GPS before you start moving. Since a plane moves reasonably fast, it can be hard for your GPS to locate an initial signal lock. Try setting up your GPS before you start moving. Being in a still position will ensure that a better signal is located.
To get the best possible signal, you have to be prepared to use a bit more battery than you normally would. It's a necessary sacrifice, and you can always reverse it later when you don't need to use GPS.
iPhone - For our Lone Worker apps, the setting can be found on the Settings > Location Accuracy page.
Android - Go to Settings > Location and make sure that Location services are switched On. Under the Location Sources category, tap Mode and make sure it's set to High accuracy. This will use more battery, but will utilize all available wireless networks to get the best possible signal.
Ensure the date, time, and time zone are correctly set on the device (e.g. Settings > General > Date & Time). If possible, use Set Automatically. Important: Incorrect settings on your computer can sync to your device. Verify the date, time, and time zone on any computer that syncs with your device. Restart your device.
Verify that you have a cellular or Wi-Fi network connection. This allows the Assisted GPS (A-GPS) on the device to locate visible GPS satellites faster, in addition to providing initial location information using the Wi-Fi or cellular networks.
GPS / phone hardware goes out of date fairly quickly. Newer GPS chipsets tend to achieve lock faster, and achieve a more accurate signal.
Find where your GPS antenna is located on your phone. Sometimes it'll be on the same side as the screen, but on an iPhone it is on the back. So having the screen pointing downwards may work best for an iPhone.
Some phones will allow you to connect external GPS units to them. Some external GPS's will allow an aerial as well, which will further improve your signal. Such devices can plug directly into your phone or connect via bluetooth. Such units are often much more accurate than the built in location services.