CODEWITHSUNDEEP
objective-ciosgeolocationgeocoding
Zhen
Zhen

Reputation: 12431

Objective C: How to list set of locations with the nearest geolocation

I have compiled a list of locations with latitude and longitude information. Can I check what is the best approach to filter and populate the list of "nearest" geolocations in a table and mapview based on my current location? (or a destination entered by a user). Also is it also possible to indicate what is the radius I am interested in? e.g. only select all the nearest bookstores within 5km from my location etc

Appreciate your advice on this

Zhen Hoe

Upvotes: 0

Views: 3156

Answers (3)

Rayfleck
Rayfleck

Reputation: 12106

Maybe I'm missing something, but why don't you just add your locations to a mapView, and center the map on the user's current location or whereever they want? MapKit will do all the calculations for you, and only show the ones near the center. The user can set their own radius by zooming in and out. MapKit is highly optimized for exactly this purpose, that's how you can see the "rain of pins" in real time.

Update: You can also go the other way: once you have the annotations on the map, you can query the map for those annotations that are in the visible region with:

- (NSSet *)annotationsInMapRect:(MKMapRect)mapRect

From the docs:

This method offers a fast way to retrieve the annotation objects in a particular portion of the map. This method is much faster than doing a linear search of the objects in the annotations property yourself.

Upvotes: 4

petershine
petershine

Reputation: 3200

You may find - (CLLocationDistance)distanceFromLocation:(const CLLocation *)location to be very useful http://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocation_Class/CLLocation/CLLocation.html#//apple_ref/occ/instm/CLLocation/distanceFromLocation:

Upvotes: 3

zpasternack
zpasternack

Reputation: 17898

The haversine formula is frequently used to in navigation for calculating distances between coordinates. This is a pretty decent resource for distance calculations, and even has a code sample for haversine (though it is in Javascript).

If your list of locations is relative small (hundreds, even), you can probably just iterate through the whole list and calculate the distance between each place against current location.

Upvotes: 1

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