The Spectrum of Location Accuracy
Location isn't just GPS. It's a combination of GPS, WiFi positioning, and cellular towers. You must choose the right accuracy for your use case: "Navigational" (highest battery drain, high precision) vs "Significant Change" (low battery, 500m precision). Requesting more precision than you need is the fastest way to drain a user's battery.
Implementing Geofences
Geofencing allows you to trigger actions when a user enters or exits a specific circular area. It is handled at the OS level, meaning your app doesn't need to be running for it to work. Use it for "Welcome" notifications at stores or "Don't forget" reminders when leaving home. Limit the number of active geofences (typically 20 per app) to maintain performance.
Background Tracking & Battery Drain
If you need to track a route (like a fitness app), use "Deferred Location Updates." This allows the GPS chip to batch data and send it to your app in chunks, letting the CPU sleep in between. For non-real-time needs, use the "Significant Location Change" service, which triggers only when the user moves between cell towers.
iOS Core Location Framework
iOS is very strict with location. You must include NSLocationWhenInUseUsageDescription and NSLocationAlwaysAndWhenInUseUsageDescription in your Info.plist. Since iOS 14, users can provide "Approximate Location," giving you a 10-mile radius instead of an exact address. Your app must be designed to function with reduced precision.
Android Fused Location Provider
On Android, use the FusedLocationProviderClient from Google Play Services. It intelligently manages the different sensors to provide the best location with the lowest power cost. Handle the different permission levels (Fine vs Coarse) and the "Background Location" permission, which requires a separate, explicit user approval in the settings app.
A location-heavy app that doesn't optimize for battery will be the first one a user uninstalls after seeing their battery stats.
The Privacy First Approach
Only ask for location when you actually need it. Explain why you need it through an "In-App Rationale" before showing the system dialog. Give users an easy way to see what location data you've collected and a way to delete it. Transparency builds trust.
Testing Location Scenarios
Use the Xcode debugger to simulate different locations or "Driving" routes. On Android, use "Mock Location" apps. Test edge cases: What happens in a tunnel? What if the user disables GPS mid-route? Ensuring your app handles these gracefully is the difference between a pro app and a hobby project.