GPS Manager User Manual -- Routes

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## Routes

Routes may happen to have waypoints that were permanently deleted by the user (`Forget` button in waypoint window). In this case the values of distances and bearings for such points and the total distance will not be shown. Saving, exporting or displaying a route with undefined waypoints will be prevented with a warning.

A route can be created from a track : see below.

A route can be changed or created by drawing on the map as explained below.

To change a route stage a double-click with the mouse left-button should be made on one of the stage fields in the route edit window. An edit window will pop up that must be used and closed before going on.

Changes in a waypoint belonging to a route being edited/inspected will be reflected in the route window.

When modifying a route the coherence of its waypoints and its stages cannot be checked by GPSMan. For instance, when adding a new waypoint after another one the stage starting from the latter is not affected, and when replacing a waypoint by another one the stages ending on and starting from it are not affected.

The edit window for routes allows some operations on routes that may be useful. They are:

- "Invert": take the route from the last to the first waypoint;
- "Chop head": all waypoints from the first to and including the one selected are deleted; if there is no selection the first waypoint is deleted;
- "Chop tail": all waypoints from and including the one selected to the last are deleted; if there is no selection the last waypoint is deleted;
- "Include before", or "Include after": include the route (whose number was selected in the sub-menu) before or after the selected waypoint; if there is no selection, the inclusion will be done before the first or after the last waypoint, respectively.
- "Clear": delete all waypoints.

A route can be converted into a track from the route window.

An elevation graph for a route can be plotted from the route window and subsequently saved as a Postscript file if there are at least 3 waypoints with a valid altitude field.

The area enclosed by a route can be computed under the following conditions -- badly wrong values will result if they are not met! The route stages are taken as sides of a polygon and if the last waypoint is not the same as the first, a "virtual" side from the first to the last waypoint is considered. The polygon must be non-intersecting: there can be no multiple occurrences of waypoints (apart from the first one being also the last) and no intersections of the polygon sides. GPSMan will only check for multiple occurrences of waypoints. The method for computing areas is an approximate method that is not reliable when there are sides of the polygon too small when compared to others or there are very small angles between the sides. Results of area computations should be used with care and if possible checked against results of other forms of area measurement.

The details of the area computation are as follows. An algorithm for computing the area of a (non-self intersecting) polygon on the sphere is first tried out. If there are very small intermediate values that may indicate approximation errors, the area is computed by first projecting the polygon onto the plane (using the Transverse Mercator projection centred at the first point of the polygon) and applying then an algorithm for computing the area of a (non-self intersecting) polygon on the plane. A warning message is issued if this happens.

|  |  | Routes