The appearance of the Location Services icon in your device's status bar does not mean that GPS on your device is continuously running (for more information on Apple Location Services, click here). The iOS Location Services icon indicates that one or more apps have accessed your device’s location within a certain period of time.
To view which apps have recently accessed your current location go
to your device’s iOS Settings (Settings > Privacy > Location
Services) then scroll through the list of apps on your device to see
which apps have permission to access your location. A purple Location
Services icon will appear next to an item that has recently used your
location. A gray Location Services icon will appear next to an item that
has used your location within the last 24 hours. An outlined Location
Services icon will appear next to an item that is using a geofence.
Storm Shield uses the Significant-Change Location service (not GPS) of iOS Location Services in order to notify you of weather alerts for your current location. This provides a low-power way for apps to get a device's current location without using GPS and still be notified when significant changes occur. This has a minimal effect on battery life. Battery life depends on a variety of factors such as the version of iOS your device uses, the age of your device and its battery, and other apps using your location.
The iOS7 Background App Refresh feature is used in conjunction with Significant-Change Location to ensure Storm Shield is aware of current location changes so you receive weather alerts wherever you travel.