Minimum distance to plot points on UIMapview - iphone

Question

my query is whats the minimum distance required to plot point on a UIMAPVIEW, so that they could be shown as distinct points.
For e.g., suppose if there are users in same apartment, their would be hardly any distance between their latitude-longitude. So how do i differentiate them !

Answer 1

There are usually two ways - one is clustering, which means you use a marker with a number that indicates how many underlying markers there are. When tapping on that, the user is then shown the separate markers (or a recursive zoom-in that splits the markers up more and more). Superpin (www.getsuperpin.com) is one example, but there are others out there.
Another approach is to actually offset the marker from its real location. For this, you need some kind of distribution algorithm that offsets it just enough - that is, set the markers as close together as possible while still giving them enough surface area to be seen/touched. For this, we use Fibonacci's Sunflower patten. What you'd have to do is identify all the Annotations that have the same coordinate, group them, and then draw each group in a sequence while offsetting one from the other - for ex. have some code that iterates along a spiral shape and drops down markers along that spiral.
Can put up sample code etc to help if you're wanting to go with the second approach, let me know.
EDIT: I found some code we wrote for this, but it's not objective C. Can you read it?
class SunFlower
{
static $SEED_RADIUS = 2;
static $SCALE_FACTOR = 4;
static $PI2 = 6.28318531; // PI * 2
static $PHI = 1.61803399; // (sqrt(5)+1) / 2
public static function calcPos($xc, $yc, $factor, $i)
{
$theta = $i * SunFlower::$PI2 / SunFlower::$PHI;
$r = sqrt($i) * $factor;
$x = $xc + $r * cos($theta);
$y = $yc - $r * sin($theta);
if ($i == 1) {
$y += ($factor * 0.5);
}
return array($x, $y);
}
}