MapComp imposes a limit of fifty (50) descriptors per map file, and therefore 50 object commands per input file.
| Object Command Elements | |
| object | Command name. |
| Object Type | The type of objects to be included in the descriptor, as listed below. |
| SW Lat/Long | Latitude and longitude of the south west corner of the descriptor area. |
| NE Lat/Long | Latitude and longitude of the north east corner of the descriptor area. |
| Name Length | The length of names. Only applies to type NamedPoint and types derived from it (i.e., TurnPoint). Field must be omitted for all other types. Zero indicates that names are variable length. Described under the .TPS file below. |
The name of the object type must be spelled exactly as in the table below, in upper and lower case as shown. The object types currently supported are:-
| Object Types | |
| Line | Generic line feature, normally one of those shown below would be used. Displayed in white by EWView. |
| CoastLine | Edge of sea or lake, displayed in blue by EWView. |
| AirspaceBoundaryLine | Edge of controlled airspace, displayed in magenta by EWView. |
| GroundFeatureLine | Road, airfield perimeter, runway, etc., displayed in brown by EWView. |
| NamedPoint | Point on the ground with a name, such as a town or airfield, not used as a turn point. Displayed in white be EWView. |
| TurnPoint | Point used as a start point, turn point, finish point or finish line end. Displayed in yellow by EWView. |
The SW corner and NE corner define the latitude and longitude boundaries of the area to be included in the descriptor. The purpose of dividing objects of one type into different areas is to allow EWView to display them quickly.
Only objects totally inside the area are included - line features which cross the area boundary are not included. Points which are on the boundary are considered to be included.
Each object in the input files is considered against each object command in the .MAP file in turn, starting with the first and proceeding in the order in which they are given. The first command which has the same type as the object and which has an area which includes every point in the object is considered to match.
See the ignore-uncontained command for more information on what happens if no object command matches an object in the input files.
A common technique is to have a number of small boxes to split up the bulk of the data for quick display followed by an all encompassing larger box to catch items not included in any of the smaller boxes - perhaps because they cross the boundaries between them.
In the following example the first two object commands split the coastlines of New Zealand into roughly the South and North Islands. The third object command catches any fragments left over.
|
object CoastLine S47°00.00' E165°00.00' S40°00.00' E175°00.00' object CoastLine S42°00.00' E172°00.00' S34°00.00' E179°00.00' object CoastLine S50°00.00' E160°00.00' S30°00.00' E179°59.00' |