A modern phone or tablet can locate itself in a number of ways, but the two main systems used for evaluating your location are your wifi connection when present and GPS.
GPS – just about all modern phones have an in-built GPS receiver. Not all modern tablets have an in-built GPS.
A GPS receiver listens for very precise radio signals from satellites and then triangulates your position from those signals. GPS receivers work best with a clear view of the sky.
A modern phone can now report your location to an accuracy of around 3m.
GPS Battery Consumption
The GPS when ON consumes a considerable amount of battery. How fast your battery will be depleted depends on several factors, including: the age of your phone, the age and condition of your battery and atmospheric and local conditions. But by far the greatest consumer is the screen and its brightness. To conserve energy always keep you screen off when not in use and the brightness as low as possible when it is.
If you are just ´spotting´ your location – i.e. you stop, turn the GPS on, see your position on the map, turn the GPS off, then unless you are spotting continually, or have the screen on your phone turned on the whole day, battery life should not be an issue for you.
If you are recording a trackog, then the GPS is on continually, and battery consumption will be much higher. As a rule of thumb, on an average modern phone you should expect to consume about 10% of your battery per hour recording a tracklog. Some people will do better, some will do worse.
There are plenty of options for external battery packs for phones, so it´s easy to carry a battery from which to charge your phone or tablet. These are now easily available and quite cheap.
Bluetooth GPS units
Another approach is not to use the in-built GPS unit, but to purchase a Bluetooth enabled GPS device. This will connect to your phone or tablet via a wireless Bluetooth connection. As the GPS unit has its own battery it will not drain the battery of your phone or tablet. Some people also like this approach as they can place the GPS at the top of their rucksack where it will have a good view of the sky compared to the pocket into which you are most likely carrying your phone or tablet.
Location from WiFi
A wifi connection gives a very coarse location, however it has two advantages over GPS. If you already have your wifi radio turned on, you don´t need to power on the GPS which is an extra pull on your phones battery. The second advantage is that you do not need a clear view of the sky.
However, in reality the wifi position is not of sufficient precision for navigation, its more suited to knowing which town you are in for a local weather forecast.
We have mentioned the wifi location, as if your device doesn´t have a built in GPS, you may find OMN will put you approximately on the map whilst at home and you think you have a GPS – it is however just working from the position provided from a wifi location. When you leave home, it will therefore cease to work as you disconnect from your home wifi.
A Note on iPads
The cellular chip in an iPad also contains a GPS receiver. Therefore, unless you have purchased an iPad with cellular access, you will not have a GPS receiver in your iPad. Please note, if you have a cellular enabled iPad, you don’t need a sim card or internet access for the GPS to work, it`s just that Apple bundles the cellular and GPS into one module.
If you do have a wifi only iPad (or even a cellular one), you can connect a Bluetooth GPS module and have full GPS access inside OMN. Some people actually prefer this approach as it means the GPS is not using the battery of the iPad.