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http://blog.asolutions.com/2010/09/building-custom-map-annotation-callouts-part-1/

The iPhone’s Map Annotation Callouts are very useful for displaying small amounts of information
when a map pin (annotation) is selected. One problem with the standard callouts present in iOS
is the inability to change the height of the callout.

For example, you may want to display a logo or other image 
that is taller than the default callout. Or you may want to display an address and phone number
on separate lines under the title. Both of these scenarios are impossible using the standard iOS
callouts. There are many steps to building a good replacement callout with the proper look 
and behavior, but it can be done.


Dowmload-http://blog.asolutions.com/wp-content/uploads/2010/09/CustomMapAnnotationBlogPart1.zip

http://www.raywenderlich.com/30001/overlay-images-and-overlay-views-with-mapkit-tutorial



t’s quite easy to add a map into your app using MapKit.
But what if you want to decorate or customize the map provided by Apple 
with your own annotations and images?
Luckily, Apple provides and easy way to do this with Custom Overlay Views.
In this tutorial, you create an app for the Six Flags Magic Mountain amusement park.
If you’re a roller coaster fan in the LA area, you’ll be sure to appreciate this app :]
Just think about what a visitor to the park would be interested in. 
Things like the location of specific attractions, routes to the various rides
and roller coasters, and the location of characters around the park. 
These are perfect candidates for custom overlay images – and that’s exactly
what you’ll be adding in this tutorial.