In many iPhone application development projects that I have done, I had to work on Geo-fencing feature i.e. It should prompt an alert to user (“You are nearby X place”) when user is passing through any location within certain radius.
So when I was developing such iOS applications, it was practical and assumed that I cannot go to all places and test the application, so for such kind of testing with live records I have used below function to change/transfer user’s geo-location to any particular area.
For this you have to take arbitrarily any location and use your current location to find out offset values and get it done as explained below. To transform any location to any other area on geographical plan you need to apply offset values on the current latitude and longitude of user location.
Kindly follow below steps to transform any points to other plan. It is explained using one of the iOS features related to “Settings” bundle. Because that way you can change offset very quickly without doing statically within an application.
How to create setting bundle with Offset points ?
Add setting bundle into your application:
Add two text field and set their values as shown in below image.
In a common method class or in application delegate file you will have to write down below two methods. One method is responsible to apply offset value on latitude for current location and another is for longitude.
Method-1:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | // Method that fetches latitude offset value from the setting and apply on the latitude. - (double)applyLatitudeOffset:(double) latitude { double latitudeOffset = 0.0; NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; if ([defaults objectForKey:@"LatOffset"] == nil) { return latitude; } if ([[defaults objectForKey:@"LatOffset"] length] == 0) { return latitude; } latitudeOffset = [[defaults objectForKey:@"LatOffset"] doubleValue]; double newLatitude; newLatitude = latitude + latitudeOffset; return newLatitude; } |
Method-2:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | // Method that fetches longitude offset value from the setting and apply on the longitude value. - (double)applyLongitudeOffset:(double) longitude { double longitudeOffset = 0.0; NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; if ([defaults objectForKey:@"LongOffset"] == nil) { return longitude; } if ([[defaults objectForKey:@"LongOffset"] length] == 0) { return longitude; } longitudeOffset = [[defaults objectForKey:@"LongOffset"] doubleValue]; double newLongitude; newLongitude = longitude + longitudeOffset; return newLongitude; } |
How to calculate Offset Values to set under “Settings” ?
You need to have your current location and desire location where you would like to move your current position. Below examples shows how you can calculate offset value.
Example:
Current Location:
Latitude : 23.031715
Longitude : 72.565338
Desired Location:
Latitude : 37.578313
Latitude : -122.347146
Offset values:
Latitude Offset : (37.578313 – 23.031715) = 14.546598
Longitude Offset : (-122.347146 – 72.565338) = -194.912484
How to set offset value in an application?
Once you install application in your device, go to default settings it will list your application under it.
Once you select your application – you will find screen like below where you need to enter your calculated offset values.
How to apply offset values on current location?
Please find below sample code using which you can apply offset on the current location.
1 2 3 4 5 6 7 8 9 | AppDelegate * delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate]; // Current location latitude and longitude double current_latitude = 23.031715; double current_longitude = 72.565338; // Here are new latitude and longitude double new_latitude = [delegate applyLatitudeOffset:current_latitude]; double new_longitude = [delegate applyLongitudeOffset:current_longitude]; |
This is how we can transform our current location to any other point.
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Very useful article, thanks…