iPhone Map Kit cluster pinpoints - iphone

Question

Regarding iPhone Map Kit cluster pinpoints:
I have 1000's of marks that I want to show on the map but it's just too many to handle so I want to cluster them.
Are there frameworks available or proof of concepts? That this is possible or is already been done?

Answer 1

You can use REVClusterMap to cluster

Answer 2

Note: This is a commercial product I'm affiliated with, but it solves this very problem.
I solved this problem in few of my apps and decided to extract it into a reusable framework. It's called Superpin and it is an (commercial, license costs $149) iOS Framework that internally uses quadtrees for annotation storage and performs grid-based clustering. The algorithm is quite fast, the included sample app is showing airports of the world (more than 30k+ annotations) and it's running quite smooth on an 3G iPhone.

Answer 3

This might be a bit like using a chainsaw to mow the lawn, but here is an excerpt from Algorithms in a Nutshell
Creating a KD-Tree...
public class KDFactory {
// Known comparators for partitioning points along dimensional axes.
private static Comparator<IMultiPoint> comparators[ ] ;
// Recursively construct KDTree using median method on input points.
public static KDTree generate (IMultiPoint [ ] points) {
if (points. length == 0) { return null; }
// median will be the root.
int maxD = points[ 0] . dimensionality( );
KDTree tree = new KDTree(maxD) ;
// Make dimensional comparators that compare points by ith dimension
comparators = new Comparator[ maxD+1] ;
for (int i = 1; i <= maxD; i++) {
comparators[ i] = new DimensionalComparator(i) ;
}
tree. setRoot(generate (1, maxD, points, 0, points. length-1) ) ;
return tree;
}
// generate the node for the d-th dimension (1 <= d <= maxD)
// for points[ left, right]
private static DimensionalNode generate (int d, int maxD,
IMultiPoint points[ ] ,
int left, int right) {
// Handle the easy cases first
if (right < left) { return null; }
if (right == left) { return new DimensionalNode (d, points[ left] ) ; }
// Order the array[ left, right] so the mth element will be the median
// and the elements prior to it will all be <=, though they won' t
// necessarily be sorted; similarly, the elements after will all be >=
int m = 1+(right-left) /2;
Selection. select(points, m, left, right, comparators[ d] ) ;
// Median point on this dimension becomes the parent
DimensionalNode dm = new DimensionalNode (d, points[ left+m-1] ) ;
// update to the next dimension, or reset back to 1
if (++d > maxD) { d = 1; }
// recursively compute left and right sub-trees, which translate
// into ' below' and ' above' for n-dimensions.
dm. setBelow(maxD, generate (d, maxD, points, left, left+m-2) ) ;
dm. setAbove(maxD, generate (d, maxD, points, left+m, right) ) ;
return dm;
}
}
Finding nearest neighbors best: O(log n) worst O(n)
// method in KDTree
public IMultiPoint nearest (IMultiPoint target) {
if (root == null) return null;
// find parent node to which target would have been inserted. This is our
// best shot at locating closest point; compute best distance guess so far
DimensionalNode parent = parent(target) ;
IMultiPoint result = parent. point;
double smallest = target. distance(result) ;
// now start back at the root, and check all rectangles that potentially
// overlap this smallest distance. If better one is found, return it.
double best[ ] = new double[ ] { smallest };
double raw[ ] = target. raw( );
IMultiPoint betterOne = root. nearest (raw, best) ;
if (betterOne ! = null) { return betterOne; }
return result;
}
// method in DimensionalNode. min[ 0] contains best computed shortest distance.
IMultiPoint nearest (double[ ] rawTarget, double min[ ] ) {
// Update minimum if we are closer.
IMultiPoint result = null;
// If shorter, update minimum
double d = shorter(rawTarget, min[ 0] ) ;
if (d >= 0 && d < min[ 0] ) {
min[ 0] = d;
result = point;
}
// determine if we must dive into the subtrees by computing direct
// perpendicular distance to the axis along which node separates
// the plane. If d is smaller than the current smallest distance,
// we could "bleed" over the plane so we must check both.
double dp = Math. abs(coord - rawTarget[ dimension-1] ) ;
IMultiPoint newResult = null;
if (dp < min[ 0] ) {
// must dive into both. Return closest one.
if (above ! = null) {
newResult = above. nearest (rawTarget, min) ;
if (newResult ! = null) { result = newResult; }
}
if (below ! = null) {
newResult = below. nearest(rawTarget, min) ;
if (newResult ! = null) { result = newResult; }
}
} else {
// only need to go in one! Determine which one now.
if (rawTarget[ dimension-1] < coord) {
if (below ! = null) {
newResult = below. nearest (rawTarget, min) ;
}
} else {
if (above ! = null) {
newResult = above. nearest (rawTarget, min) ;
}
}
// Use smaller result, if found.
if (newResult ! = null) { return newResult; }
}
return result;
}
More on KD-Trees at Wikipedia

Answer 4

I tried the others suggested here, and I also found OCMapView which has worked the best.
Its free and allows for easy grouping of annotations, which is what I needed. Its a bit newer & more updated than Revolver and to me is easier to implement.

Answer 5

A proof of concept is the Offline Maps app "OffMaps" ;)
http://itunes.apple.com/us/app/offmaps/id313854422?mt=8

Answer 6

I recently had to implement annotation clustering with MapKit. The solutions mentioned above are good, depending on your use case. I ended up going with FBAnnotationClustering (Objective-C) because it was free, and had lots of stars and few issues on github:
https://github.com/infinum/FBAnnotationClustering
The app I was working on was very map-centric, so it made sense to translate FBAnnotationClustering into Swift. Here's a blog post on the approach, which includes a link to the sample project on github.
http://ribl.co/blog/2015/05/28/map-clustering-with-swift-how-we-implemented-it-into-the-ribl-ios-app/

Answer 7

Inspired by WWDC 2011 video, this code works very well for me. Maybe not the fastest of all proposed here but it's for free and it's definitely the simplest.
It basically use 2 maps. One is hidden and hold every single annotation (allAnnotationMapView in my code). One is visible and show only the clusters or the annotations if single (mapView in my code).
- (void)didZoom:(UIGestureRecognizer*)gestureRecognizer {
if (gestureRecognizer.state == UIGestureRecognizerStateEnded){
[self updateVisibleAnnotations];
}
}
- (void)updateVisibleAnnotations {
static float marginFactor = 2.0f;
static float bucketSize = 50.0f;
MKMapRect visibleMapRect = [self.mapView visibleMapRect];
MKMapRect adjustedVisibleMapRect = MKMapRectInset(visibleMapRect, -marginFactor * visibleMapRect.size.width, -marginFactor * visibleMapRect.size.height);
CLLocationCoordinate2D leftCoordinate = [self.mapView convertPoint:CGPointZero toCoordinateFromView:self.view];
CLLocationCoordinate2D rightCoordinate = [self.mapView convertPoint:CGPointMake(bucketSize, 0) toCoordinateFromView:self.view];
double gridSize = MKMapPointForCoordinate(rightCoordinate).x - MKMapPointForCoordinate(leftCoordinate).x;
MKMapRect gridMapRect = MKMapRectMake(0, 0, gridSize, gridSize);
double startX = floor(MKMapRectGetMinX(adjustedVisibleMapRect) / gridSize) * gridSize;
double startY = floor(MKMapRectGetMinY(adjustedVisibleMapRect) / gridSize) * gridSize;
double endX = floor(MKMapRectGetMaxX(adjustedVisibleMapRect) / gridSize) * gridSize;
double endY = floor(MKMapRectGetMaxY(adjustedVisibleMapRect) / gridSize) * gridSize;
gridMapRect.origin.y = startY;
while(MKMapRectGetMinY(gridMapRect) <= endY) {
gridMapRect.origin.x = startX;
while (MKMapRectGetMinX(gridMapRect) <= endX) {
NSSet *allAnnotationsInBucket = [self.allAnnotationMapView annotationsInMapRect:gridMapRect];
NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];
NSMutableSet *filteredAnnotationsInBucket = [[allAnnotationsInBucket objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL isPointMapItem = [obj isKindOfClass:[PointMapItem class]];
BOOL shouldBeMerged = NO;
if (isPointMapItem) {
PointMapItem *pointItem = (PointMapItem *)obj;
shouldBeMerged = pointItem.shouldBeMerged;
}
return shouldBeMerged;
}] mutableCopy];
NSSet *notMergedAnnotationsInBucket = [allAnnotationsInBucket objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL isPointMapItem = [obj isKindOfClass:[PointMapItem class]];
BOOL shouldBeMerged = NO;
if (isPointMapItem) {
PointMapItem *pointItem = (PointMapItem *)obj;
shouldBeMerged = pointItem.shouldBeMerged;
}
return isPointMapItem && !shouldBeMerged;
}];
for (PointMapItem *item in notMergedAnnotationsInBucket) {
[self.mapView addAnnotation:item];
}
if(filteredAnnotationsInBucket.count > 0) {
PointMapItem *annotationForGrid = (PointMapItem *)[self annotationInGrid:gridMapRect usingAnnotations:filteredAnnotationsInBucket];
[filteredAnnotationsInBucket removeObject:annotationForGrid];
annotationForGrid.containedAnnotations = [filteredAnnotationsInBucket allObjects];
[self.mapView addAnnotation:annotationForGrid];
//force reload of the image because it's not done if annotationForGrid is already present in the bucket!!
MKAnnotationView* annotationView = [self.mapView viewForAnnotation:annotationForGrid];
NSString *imageName = [AnnotationsViewUtils imageNameForItem:annotationForGrid selected:NO];
UILabel *countLabel = [[UILabel alloc] initWithFrame:CGRectMake(15, 2, 8, 8)];
[countLabel setFont:[UIFont fontWithName:POINT_FONT_NAME size:10]];
[countLabel setTextColor:[UIColor whiteColor]];
[annotationView addSubview:countLabel];
imageName = [AnnotationsViewUtils imageNameForItem:annotationForGrid selected:NO];
annotationView.image = [UIImage imageNamed:imageName];
if (filteredAnnotationsInBucket.count > 0){
[self.mapView deselectAnnotation:annotationForGrid animated:NO];
}
for (PointMapItem *annotation in filteredAnnotationsInBucket) {
[self.mapView deselectAnnotation:annotation animated:NO];
annotation.clusterAnnotation = annotationForGrid;
annotation.containedAnnotations = nil;
if ([visibleAnnotationsInBucket containsObject:annotation]) {
CLLocationCoordinate2D actualCoordinate = annotation.coordinate;
[UIView animateWithDuration:0.3 animations:^{
annotation.coordinate = annotation.clusterAnnotation.coordinate;
} completion:^(BOOL finished) {
annotation.coordinate = actualCoordinate;
[self.mapView removeAnnotation:annotation];
}];
}
}
}
gridMapRect.origin.x += gridSize;
}
gridMapRect.origin.y += gridSize;
}
}
- (id<MKAnnotation>)annotationInGrid:(MKMapRect)gridMapRect usingAnnotations:(NSSet *)annotations {
NSSet *visibleAnnotationsInBucket = [self.mapView annotationsInMapRect:gridMapRect];
NSSet *annotationsForGridSet = [annotations objectsPassingTest:^BOOL(id obj, BOOL *stop) {
BOOL returnValue = ([visibleAnnotationsInBucket containsObject:obj]);
if (returnValue) {
*stop = YES;
}
return returnValue;
}];
if (annotationsForGridSet.count != 0) {
return [annotationsForGridSet anyObject];
}
MKMapPoint centerMapPoint = MKMapPointMake(MKMapRectGetMinX(gridMapRect), MKMapRectGetMidY(gridMapRect));
NSArray *sortedAnnotations = [[annotations allObjects] sortedArrayUsingComparator:^(id obj1, id obj2) {
MKMapPoint mapPoint1 = MKMapPointForCoordinate(((id<MKAnnotation>)obj1).coordinate);
MKMapPoint mapPoint2 = MKMapPointForCoordinate(((id<MKAnnotation>)obj2).coordinate);
CLLocationDistance distance1 = MKMetersBetweenMapPoints(mapPoint1, centerMapPoint);
CLLocationDistance distance2 = MKMetersBetweenMapPoints(mapPoint2, centerMapPoint);
if (distance1 < distance2) {
return NSOrderedAscending;
}
else if (distance1 > distance2) {
return NSOrderedDescending;
}
return NSOrderedSame;
}];
return [sortedAnnotations objectAtIndex:0];
}

Answer 8

I think Foto Brisko (iTunes link) does this.
I do not think there is a Cocoa Touch framework for it.