Visual navigation is a technique often employed in light aircraft, which operate at relatively low speeds and heights, when weather is good and visual contact can be maintained with the ground for most of the flight.
Poor visual navigation is often cited as a cause of airspace infringement.
As with other modes of navigation, pre-flight preparation is extremely important.
After aeronautical information, including NOTAMs, has been checked and a meteorological briefing obtained, the route must be selected and marked on the map, avoiding controlled airspace, danger areas, etc.; or if it is intended to enter controlled airspace for part of the flight, the point of entry and departure must be plotted and defined by reference to a radio beacon or airway reporting point.
The route should be selected by reference to a topographical map, so that best use is made of ground features to facilitate navigation; for example, the route might follow a line feature (e.g. a coastline, railway or river) and turn at easily identified positions (e.g. a railway intersection, lake, or prominent town).
Ideally, a topographical map marked with airspace restrictions should be used.
Care should be taken to ensure that line features and turning points selected are unique.
A simple flight plan showing planned levels, mean tracks, distance and time between turning points, and minimum safe altitude should be prepared.
Timing marks should be marked along tracks to aid searching for and verification of ground features.
Flying the Route
Fold the map so that it is easy to use in the cockpit, and so that it unfolds naturally to follow the route. Hold the map so that the direction of flight is at the top - not North; by doing this, 'left' on the map will correspond to 'left' on the ground and map reading will be much easier.
Always be aware of the minimum safe altitude and the location of airspace reservations - above and below as well as on either side of track.
Keep a good look-out for other aircraft, including microlights and gliders. Approaching a turning point, look along the new track for other aircraft, for weather, and for obstacles or rising ground.
Navigating from Map to Ground or from Ground to Map
The easiest way to navigate visually is by selecting ground features which are marked on the map and looking for them on the ground. If the weather is fine, this is not difficult provided that unique, prominent ground features have been chosen. However, if there is cloud below or the visibility is poor it may be difficult to find the selected features.
In bad weather, the best solution is to navigate from ground to map. Look for prominent features on the ground through holes in the cloud, then identify them on the map. The flight plan timings can be used to help in this, but care should be taken because, depending on the map scale, certain features that are easy to see from the air may not be marked on the map. For really important check points, (e.g. when approaching an airway) a line feature, such as a railway line or coastline, is usually better than an isolated point, because it is quick and easy to see.
Also modern navigation systems based on GPS can be used as a supplementary mean of navigation. However, such systems must be certified so they are very expensive for the normal VFR flying. An extensive list of GPS-based navigation tools is available here: VFR navigation tools table.
Plan to enter or cross controlled airspace at a navigation aid or reporting point and make the track cross at right angles so that minimum time is spent in controlled airspace. Calculate the ETA to the edge of controlled airspace accurately, by reference to a really reliable visual fix. Always mark the point where you will turn back if you haven’t got clearance.
EUROCONTROL Airspace Infringement Initiative
EUROCONTROL Guidance Notes for GA pilots
EGAST Safety promotion leaflet for general aviation pilots