The drawing area
The center of the map is at the location you specified in the LOCATION tab (FILE\ PROJECT SETTINGS..., see above). You will notice the grid covering the drawing area. There are three differently shaded type of grid lines which you can assign a spacing.
This is very helpful since you get a better idea of distances in your project. To change the spacing and the grid color go to FILE\ PREFERENCES... menu item and click in the GRID tab. These settings are stored along with the program's settings.
The drawing area is 10km x 10km in size (approx. 6 x 6 miles). This should be large enough to design your airport. It is very important to know that GroundMaker is there to design airports, not landscapes. Why airports only? Most airports can be considered as being flat. GroundMaker will only let you design shapes that lie flat on the ground, sloped taxiways and runways cannot be made (exception: Lines will 'follow' the ground mesh). The reason for that is because polygons are used to outline the runways and taxiways. It is merely impossible to make a sloped polygonal taxiway in FS. Only by using mesh design techniques you will be able to model the airport's surface as it is in real life. The only disadvantage here would be the huge amount of textures needed to render such an airport in detail. Polygonal design, the technique used by GroundMaker and most scenery design tools will give you the most satisfying results in the scenery's sharpness and detail.
The whole world in Flight Simulator 2000 is modeled using terrain mesh. That means that most part of the world are not flat, but sloped. Since GroundMaker can only make scenery that lies on a flat, horizontal surface, the area around the airport must be flattened. If you want to work on an already existing airport in FS, you must exclude the default scenery. Otherwise you will have double runways, taxiways or buildings...
Scenery items
Any of the items in the toolbar can be added on the map. Those items are separated into two categories: shapes and objects. Following shapes are available:
Polygon - Poly(): colored or textured.
Polygon - TexPoly(): only textured. Lets you assign a texture coordinate to every polygon point.
Lines/Roads: use them as taxiway centerlines or roads.
Dotted lines: usually for night effects. For taxiway side lights.
Tree lines: they give the illusion of woods surrounding the airport.
Voluminous forests: they look like tree lines, except they are 'closed' and covered with a 3-D forest texture.
One flatten polygon: required in order to have a scenery free of visual artifacts in FS. Makes a flat surface at the airport's altitude.
Following objects are available:
Runways
3-D objects (API macros): use GroundMaker's objects or import your own.
Taxiway signs
Navigation: VORs and NDBs.
Exclude areas
Initial location: for world menu entry.
It is recommended to make taxiways and all other ground surfaces using the Polygon-Poly() tool.