Curve Calculator

This View allows you to create a new, or edit an existing, Curve Calculation to find the distance to the Horizon and its Declination Angle, together with the amount of a Target that will be obscured.


Use the pop-up Text Keyboard to enter an optional Title to identify this Curve Calculation. The Filter Curves option in the Curve View can be used to search for Records that contain specific text in the Title.

Observer Height

Use the pop-up Numeric Keypad to enter the height of the Observer. As a guide the Altitude as determined by GPS is displayed, but you can enter a different value depending on the circumstances - e.g. if you are on a dried lakebed the GPS Altitude would not be an appropriate value to use when determining the distance to the Horizon.


The distance to the Horizon and its Declination Angle are calculated automatically whenever the Observer Height is changed. The Map View displays the Horizon as a green circle around the Observer Location. Tap on the Horizon value to cycle through Metric, Imperial and Nautical Units of Measure (the same as changing it in the Settings).

Target Distance

Use the pop-up Numeric Keypad to enter the distance to the Target. The Map View displays the Target Distance as a red circle around the Observer Location. A Target Location can be specified using the Set Target option. The amount of the Target that is obscured by the Horizon is displayed below the Target Distance.

Map  |  Hybrid  |  Satellite

Toggle between Map, Hybrid and Satellite view. You can explore the Map using the following gestures:


Scroll the Map.

Quick Zoom

Double tap to zoom in to that point.

Zoom In

Spread to zoom in.

Zoom Out

Pinch to zoom out.


If required, you can rotate the Map to reflect the direction you are heading. Tap the Compass that appears in the upper right corner of the Map to re-orientate with North to the top.

Observer Location

The Coordinates of the Observer Location are displayed below the Map, together with the Address and Country Flag. An Observer Location can be specified using the Set Observer option.