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Pilotage and dead reckoning: Difference between revisions
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=== Pilotage === | === Pilotage === | ||
Pilotage or map reading is, in fair weather and at a bit higher altitude, nearly independent of dead reckoning. The two main uses for the map is to catch any sings if drift before you have drifted to far off track and to accurately find and turn at the checkpoints. In order to effectively use the map it is usually prepared with checkpoints, tracks, minute marks and various annotations. This can be done in many ways from very simple to all the way to extremely detailed. | Pilotage or map reading is, in fair weather and at a bit higher [[altitude]], nearly independent of dead reckoning. The two main uses for the map is to catch any sings if drift before you have drifted to far off track and to accurately find and turn at the checkpoints. In order to effectively use the map it is usually prepared with checkpoints, tracks, minute marks and various annotations. This can be done in many ways from very simple to all the way to extremely detailed. | ||
One very important thing to keep in mind is that you might not have all that much time in the cockpit to read the map, i.e. the things drawn on the map ''must be unambiguous'' and be possible to read ''on a glance''. | One very important thing to keep in mind is that you might not have all that much time in the cockpit to read the map, i.e. the things drawn on the map ''must be unambiguous'' and be possible to read ''on a glance''. | ||
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=== Dead reckoning === | === Dead reckoning === | ||
Using ''dead reckoning'' is more or less the act of following, and updating, a preplanned "time table", often called a ''(VFR) navigation log'' or ''nav log''. The difference between the nav log and your local bus' time table is that the nav log, apart from times and places, in this context often called ''checkpoints'' or ''waypoints'', also include the heading, altitude and airspeed you need to have to get to the next checkpoint on time. | Using ''dead reckoning'' is more or less the act of following, and updating, a preplanned "time table", often called a ''([[VFR]]) navigation log'' or ''nav log''. The difference between the nav log and your local bus' time table is that the nav log, apart from times and places, in this context often called ''checkpoints'' or ''waypoints'', also include the heading, [[altitude]] and [[airspeed]] you need to have to get to the next checkpoint on time. | ||
==== The navigation log ==== | ==== The navigation log ==== | ||
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* Firstly, all maps show ''true'' north, while navigation almost exclusively is done by ''magnetic'' north. The winds are also reported in true north. | * Firstly, all maps show ''true'' north, while navigation almost exclusively is done by ''magnetic'' north. The winds are also reported in true north. | ||
* Secondly, the air speed shown by your airspeed indicator, the ''indicated airspeed'' or ''IAS'', is not the same as the speed you actually do have, the ''true air speed'' or ''TAS'', as there is a varying difference between them, mainly dependent on altitude. | * Secondly, the air speed shown by your [[airspeed]] indicator, the ''indicated airspeed'' or ''[[IAS]]'', is not the same as the speed you actually do have, the ''true air speed'' or ''[[TAS]]'', as there is a varying difference between them, mainly dependent on [[altitude]]. | ||
* Thirdly, unless you are flying in still air the TAS is actually not the speed you have over the ground, the ''ground speed'' or ''GS''. If you have a ''head wind'' coming towards you, your GS will be slower than your TAS, and the opposite if you have a ''tail wind'' coming from behind. | * Thirdly, unless you are flying in still air the TAS is actually not the speed you have over the ground, the ''[[ground speed]]'' or ''GS''. If you have a ''head wind'' coming towards you, your GS will be slower than your TAS, and the opposite if you have a ''tail wind'' coming from behind. | ||
* Fourthly, if you have the wind from the side, you will drift off from your track. To stay on track you will have to head into the wind. This results in that the ''(magnetic) heading'', or ''MH'', you will have to keep to get to the next checkpoint isn't the same as the direction from the last checkpoint to the next, the ''(magnetic) course'' or ''MC''. Also since the wind is pushing from the side it will change your GS, though not as much as a head or tail wind. | * Fourthly, if you have the wind from the side, you will drift off from your track. To stay on track you will have to head into the wind. This results in that the ''(magnetic) heading'', or ''MH'', you will have to keep to get to the next checkpoint isn't the same as the direction from the last checkpoint to the next, the ''(magnetic) course'' or ''MC''. Also since the wind is pushing from the side it will change your GS, though not as much as a head or tail wind. | ||
[[Category:Aviation]] | [[Category:Aviation]] | ||