The Probelm
Recently, I am developing an iOS App about real-time parking information in my University. I designed a map function in my App; however, when I used CLLocation to acquire my test-user’s location something went wrong. The coordinate that gained from the CLLocation was different from the user’s real location where showed on the map. I had no idea what happened. I double checked my implementation but found nothing wrong, so I started looking for the answer online. After I browsed a bunch of posts, I learned that it was because of my current location. I am in China Mainland right now, and the Chinese government use the different coordinate system from the international standard.
How to solve the problem
I chanced upon a framework that design by Jack Zhou named JZLocationConverter. He has designed a algorithm that could convert the WGS-84 coordinate into GCJ-02 coordinate and vice versa. This framework is available in both Object-C and Swift. This is not a perfect solution to the coordinate problem but you could get the approximate real location after the data processed by the converter.
JZLocationConverter
The JZLocationConverter is available in both Object-C and Swift; moreover, it supports CocoaPods which is a simplest way to install frameworks when you are developing an iOS App. Here are some interfaces in the JZLocationConverter:
WGS-84 -> GCJ-02 When you input a coordinate outside of China, you stil gain the WGS-84
public func wgs84Togcj02(_ wgs84Point:CLLocationCoordinate2D,result:@escaping (_ gcj02Point:CLLocationCoordinate2D) -> Void)
GCJ-02 -> WGS-84 This method has 1-2 meter error, it should be used with caution
public func gcj02ToWgs84(_ gcj02Point:CLLocationCoordinate2D,result:@escaping (_ wgs84Point:CLLocationCoordinate2D) -> Void)
You need to load the Chinese borderline before using the converter.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
JZLocationConverter.start { (error) in
if error != nil {
print("失败")
}else {
print("成功")
}
}
return true
}
You can use your custom borderline as well; consult JackZhou’s github page for additional information.
