KML File Viewer and Polygon Interaction App

Overview

This application allows users to open and parse KML (Keyhole Markup Language) files to visualize geographic data on a map. It supports displaying polygons and polylines and provides interactive features to analyze the spatial relationships of user-defined points with respect to these shapes.

Features

• Open and Parse KML Files: Load and parse KML files to extract geographic coordinates.
• Visualize Polygons and Polylines: Display the parsed data as polygons and polylines on an interactive map.
• Interactive Map: Tap on the map to check if the tapped location is inside a polygon.
• Distance Calculation: Calculate and display the shortest distance from a tapped location to the nearest edge of a polygon if the location is outside the polygon.

How It Works

1. Parsing the KML File: Uses an XML parser to read and extract coordinates from the KML file.
2. Rendering on the Map: Creates MKPolygon and MKPolyline overlays from the extracted coordinates and adjusts the map view to display them.
3. Handling User Interaction: Detects tap gestures on the map, determines the geographic coordinates of the tap, and checks if the tap location is within any displayed polygon.
4. Distance Calculation: Calculates the perpendicular distance from the tap point to the nearest edge of the polygon using vector projection.

Technical Details

• KML Parsing: Utilizes XMLParser to read and parse coordinate data from KML files.
• Map Rendering: Uses MKMapView from MapKit to display geographic data with MKPolygon and MKPolyline overlays.
• User Interaction Handling: Manages map interactions and delegate methods through a Coordinator class.
• Distance Calculation Algorithm: Iterates through each edge of the polygon and uses vector mathematics to determine the shortest distance.

Drawing the Polygon and Calculating Distance

• Drawing the Polygon:

  • The polygon is drawn using the MKPolygon class from MapKit, which renders the polygon based on an array of coordinates extracted from the KML file.

• Distance Calculation:

  • The distance from a tap point to the nearest edge of the polygon is calculated using the Point-Line Distance Algorithm.
  • This algorithm involves vector projection and the Euclidean distance formula to find the shortest distance from a point to a line segment.

Distance Calculation Formula

The formula used to calculate the distance from a tap point to the nearest edge of the polygon is based on the Euclidean distance formula. Here are the steps involved:

1. Vector Representation: Represent the line segment as a vector and calculate the vector from the tap point to a point on the line segment.
2. Projection Scalar ( t ): Calculate the scalar value ( t ) representing the projection of the tap point onto the line segment.
3. Closest Point on Segment: Find the closest point on the line segment to the tap point using the scalar ( t ).
4. Euclidean Distance: Calculate the Euclidean distance between the tap point and the closest point on the line segment.

The formula ensures accurate distance measurements from the tap point to the edges of the polygon.

Usage

1. Load a KML file into the application.
2. Visualize the geographic data on the map.
3. Tap on the map to interact with the polygons and see if a point is inside a polygon or find the distance to the nearest edge if outside.

Use Cases

• Geofencing: Determine if a point is within a designated area.
• Navigation: Visualize routes and areas of interest.
• Spatial Analysis: Analyze proximity and spatial relationships of points to polygonal areas.

Setup Instructions

1. Clone the repository to your local machine.
2. Open the project in Xcode.
3. Build and run the project on a simulator or physical device.

Contributing

If you would like to contribute to this project, please fork the repository and submit a pull request.

License

This project is licensed under the MIT License.