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Home GeoPack GeoDB Methods GetClosestItemIDIx
See also: GetClosestLatHighIx, GetClosestLatLowIx, GetClosestLongHighIx, GetClosestLongLowIx, SearchData, IxItemID, SearchForItemID, Database Item IDs 

GetClosestItemIDIx

Unit:SDL_geodb
Class:TGeoDB
Declaration:function GetClosestItemIDIx (ItemID: longint): longint;

In order to find database entries quickly TGeoDb maintains five indexes offering an ordered access to the latitudes, longitudes and item IDs of the database entries. Since a database entry may contain more than one point (e.g. country borders are polygons with many points), individual indexes are maintained both for the lowest and highest latitudes/longitudes.

The function GetClosestItemIDIx searches for an entry in the index of the item IDs (IxItemID) which is equal to ItemID. If the index does not contain any entry matching exactly the specified item ID the closest value which is greater than ItemID is selected. The function returns the element number of the index. The returned element number may take values between 1 and NumEntries+1. A value of NumEntries+1 indicates that there does not exist any value which is equal to or greater than ItemID.

Example: This method is used in the following example program (see http://www.lohninger.com/examples.html for downloading the code): geodata


Last Update: 2023-Dec-13