(Update : April, 29th 2020)
For precise positioning while saving the battery life of your tablet / smartphone, it is necessary to adjust the settings before leaving. Example with the iPad / iPhone.
One might be tempted to use the "Airplane Mode" function, which is convenient to cut off radio communication (WiFi and cellular) and thus save up battery. With Airplane Mode, only GPS receiver works to fix your location.
It is generally believed that wifi drains a little the battery (this is true) and that it is therefore not important to switch it off. But beware of possible positioning errors which may prove very adverse!
Even if your device has a very accurate GPS, the Location Services of your device use altogether wifi and cellular signals to get its position by triangulation as shown in our file. While in urban areas accuracy is good enough with cellular location, (about 5-10m), this is very different into the wild where the device will fail to make an accurate triangulation. Errors of several tens of meters can be expected in this case. This is a well known problem in sailing: while you will have a very accurate location from GPS if you sail at a distance from coast, you may find big errors close to the coast if you leave wifi and cellular on, simply because the device may detect a wifi or cellular signal and try to use it. So if you need accurate navigation, you have no choice: cut wifi and cellular with Airplane Mode function!
In terms of 3G/4G communications, the rule is simple: the further the cell tower, the more your device will "boost" its signal to try to stay connected, and will take more power. So as soon as you are too far or you no longer need a data connection, you must cut 3G/4G cellular data. This still allows to be contacted by voice calls and SMS.
On iPhone / iPad : Go to Settings> General> Cellular Network> Cellular Data = switch 0FF
Bluetooth communications are low consumers and can stay on if you use an accessory that needs them like a wireless headset or a Bluetooth GPS. Otherwise, just cut them to avoid unnecessary consumption.
On iPhone / iPad: Go to Settings> Bluetooth > switch to 0FF or ON according your need.