DirectionExplorer combines compass tool with Apple Maps to help you identify targets (villages, buildings, mountains,...) appearing in your view.
DirectionExplorer uses GPS to determine the observer's location and using the compass information draws a line on the map in the same direction the iPhone is pointing.
You can freeze the origin point and direction line to study the map in detail later.
You can also determine the length of the heading line (in miles or km) to better estimate your view. 
It is also possible to automatically calculate the horizon line distance based on the site's altitude.
The point of origin can be entered manually by tapping the map.
To help the user find the desired targets more easily, it is also possible to insert colored pins above the map.
Pins can be set by tapping in the map or entering place names.
For best results, I recommend holding the iPhone horizontally and aiming accurately.
It is also important to periodically check the application of the compass and follow the calibration information.