Why do I get extra location coordinate points when my iPhone app first launches? - objective-c

Question

I am working an iPhone app which is using CLLocationManager. When a user goes for a run, it shows the run path on a mapView. I am drawing the running path on mapView using following code:
double leastDistanceToRecord = 0.0000905;
- (void) locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
if (newLocation.horizontalAccuracy >= 0) {
if (!runoPath)
{
NSLog(#"in !runoPath if");
// This is the first time we're getting a location update, so create
// the RunoPath and add it to the map.
runoPath = [[RunoPath alloc] initWithCenterCoordinate:newLocation.coordinate];
[map addOverlay:runoPath];
self.currentRunData = [[RunData alloc] init];
[currentRunData startPointLocation:newLocation];
// On the first location update, zoom map to user location
MKCoordinateRegion region =
MKCoordinateRegionMakeWithDistance(newLocation.coordinate, 1000, 1000);
[map setRegion:region animated: NO];
}
else
{
// This is a subsequent location update.
// If the runoPath MKOverlay model object determines that the current location has moved
// far enough from the previous location, use the returned updateRect to redraw just
// the changed area.
double latitudeChange = fabs(newLocation.coordinate.latitude - oldLocation.coordinate.latitude);
double longitudeChange = fabs(newLocation.coordinate.latitude - oldLocation.coordinate.longitude);
if (latitudeChange > leastDistanceToRecord || longitudeChange > leastDistanceToRecord) {
MKMapRect updateRect = [runoPath addCoordinate:newLocation.coordinate];
if (!MKMapRectIsNull(updateRect))
{
// There is a non null update rect.
// Compute the currently visible map zoom scale
MKZoomScale currentZoomScale = map.bounds.size.width / map.visibleMapRect.size.width;
// Find out the line width at this zoom scale and outset the updateRect by that amount
CGFloat lineWidth = MKRoadWidthAtZoomScale(currentZoomScale);
updateRect = MKMapRectInset(updateRect, -lineWidth, -lineWidth);
// Ask the overlay view to update just the changed area.
[runoPathView setNeedsDisplayInMapRect:updateRect];
}
// [currentRunData updateLocation:oldLocation toNewLocation: newLocation];
}
[currentRunData updateLocation:oldLocation toNewLocation: newLocation];
// }
}
}
}
The problem is that when I start a run, I get some extra points and then because of those points I get an extraneous line on mapView that does not reflect the actual run. It even happens when I install the app on my iPhone and run it for the first time. I don't know why it's adding those extra points. Can anyone help me with that? Thanks in advance.

Answer 1

The first location you get is usually a cached location and is old. You can check the age of the location and if it is old (>60 seconds or whatever) then ignore that location update. See this answer here.
--EDIT-- If you are still having problems, put this code in didUpdateToLocation: and show us the actual output from NSLog (you can edit your question and add the output):
NSTimeInterval age = -[newLocation.timestamp timeIntervalSinceNow];
NSLog(#"age: %0.3f sec, lat=%0.2f, lon=%0.2f, hAcc=%1.0f",
age, newLocation.coordinate.latitude, newLocation.coordinate.longitude,
newLocation.horizontalAccuracy);