Every plane sighting inserted will result in a new record being created. However, it may be that the new sighting is for a plane that was already logged before. In that case the sighting is new, but the plane logged is not. Since there are now two records in the database, for the same plane with possibly only different log dates, double records might appear in views, counts and trips. In many cases this is not wanted and therefore the concept of a "new" plane is used. This will not limit the number of times a plane can be inserted, but it will limit the times it will show up in views, counts and trips. Only the sighting with the earliest log date will be used, regardless of which sighting was first inserted.
What is a new plane?
A plane is defined by the main type, registration, country and service and possibly the construction number. The construction number is in reality the single identifying number, but in practice the construction number is not always known and therefore cannot be used in all cases.
A new plane is therefore a plane for which no record yet exists with the same main type, registration, country, service (and again, possibly the same construction number if given) and an earlier log date.
Note that the determination of which plane is new is done automatically when needed. In the second example above, the Tornado logged in 2005 will be considered new for as long as the second record was not inserted yet.
Selection of new only or all planes in filters
The selection of only new planes in filters is a special case. The new field cannot be selected like all other fields as in reality, it is not a specific field in the database. A filter on new planes only can be set through a checkbox in the select box (for more info on the select box and filters see: help/filters). When this checkbox is checked only the new planes will be used in the view, count or trip. Otherwise all planes will be used.
Two indentical planes on the same day
It may happen that the same plane is logged twice on the same day. In that case the database cannot determine which is really the first sighting of the plane, as the date is recorded, but not the exact time. In cases like this the first inserted sighting will be seen as the first and therefore that sighting will be considered new (provided there is no other sighting with an earlier log date).
Logs without dates
The log date itself is not a mandatory field, it may be left empty. If no log date is given, it defaults to 0, which makes it by default the earliest possible date a plane could be logged. Therefore, when selecting new planes only, planes without a date will always be seen as the new plane.
An exception to this rule applies for counts. Since counts are always grouped by year, records with no year given are not used in counts. Even if the new filter is not used, the planes without a log date will still not be used in counts.