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.
Avoid airplane mode
One might be tempted to use the "airplane mode" setting, which is convenient to cut off all communication and thus save up battery. However this will stop also the GPS: You will no longer be positioned. This mode is thus useless in outdoor.
Cut wifi for more accuracy
It is generally believed that wifi consumes little (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, it may be tempted to use a wifi signal to get its position by triangulation as shown in our file. While in urban areas accuracy is good (about 5-10m), this is very different in open nature 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 remarkable precision from GPS if you sail at a distance from coast, you may find gross errors close to coat if you leave wifi on, simply because the device may detect a wifi signal and try to use it. So if you need precise navigation, you have no choice: cut wifi!
On iPhone / iPad : go to Settings> Wifi> switch to 0
Cut 3G for battery life
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/4Gcellular data. This still allows to be contacted by voice calls and SMS.
On iPhone / iPad : Go to Settings> General> Cellular Network> Cellular Data and 3G switch 0
Bluetooth: keep it only if you need
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 0 or I according to need