Non-bumpy taxiways (SCASM tweak)
From FSDeveloper Wiki
The bumpy taxiways with the clouds of dust behind your wheels are probably familiar to you. One of the solutions that is offered on the internet is adding an invisible runway to your scenery. I don't think this is a very elegant way to solve the problem and there even is a better solution. SCASM does have the command SurfaceType to define the type of surface for a scenery.
 Command to smooth surface
This command can be used to create a smooth surface with the following code:
Header( 1 53.3 50.9 6.9 4.3 ) LatRange( 53.3 50.9 ) Area( 5 52.307832 4.765108 20 ) RefPoint( 7 : 1 52.307832 4.765108 v1= 20000 ) SurfaceType( 0 8000 8000 0 ) EndA
This example is a piece of code for Schiphol in the Netherlands. To apply the code to your own scenery you must do the following.
First change the coordiantes in the Header and LatRange commands so that they define the boundary of your own area. Note: if you want to add more airfields to the file, the boundaries should be around all of them.
The next step is to make an Area block for each airfield. Just enter the coordinates of your airfield in the Area and RefPoint commands. Then the SurfaceType command defines a polygon that is smooth. In this example the polygon is 8000 by 8000 meters. You can of course change this to meet your own airfields size.
You must repeat this block for every airfield you want to make smooth. Then save the source code and compile it using SCASM. Now you have a separate BGL that removes the bumps!
If you want the smooth polygon to have the exact shape of the polygons of your airport, you must add a SenseBorder command to check the location of the aircraft. This way you can keep the grass on your airport bumpy, while the taxiways and aprons are smooth. I have made a tool that can generate such code automatically for you. You can find more information about it here.