----------------EDIT------------------
This version of the flattening tool has been removed.
You can find the latest version in its own thread here.
----------------------------------------
Ok, since many have reported difficulties with tileEdit, I made a tool that you can use within Orbiter and set flat areas. (Either Rect or Ellipse)
This is a request that goes in hand with what I have posted previously in this thread:
https://www.orbiter-forum.com/threads/flat-cape-canaveral-area.41771/
This editor would take the guessing out of getting flat/elevated areas. Right now, using the D3D9Client *.flt files, it's a pure guessing game of trial&error to see where you are actually editing the the terrain. It would work in tandem with the actual planetary textures so you could see the terrain you're editing.
Take the guessing out? Check.
See where you are actually editing? Check.
Works in tandem with the actual planetary textures? Check.
Here is a quick video demonstration:
Instructions:
1. Prerequisites:
You will need the extended LuaScript by
@kuddel .
Get the file "LuaScriptPlus DLLs (for Orbiter 2016).zip" from the attachments in the link below and unzip them in you Orbiter root directory:
Finally here's the Lua (sub-)Forum! My current progress and questions regarding the Orbiter Lua API will be posted here. I will update this 1st post with the current state, as soon as it changed. New items (since last edit of this post) will be marked green The attached file represents the...
www.orbiter-forum.com
2.Unzip the file attached on this post and everything will go in its place.
Usage:
- 1st Step (VERY IMPORTANT!) : Make sure that you have created a folder named Flat, in the Textures\(Name of body)\ folder of the body that you will flatten the area.

- In the Visual effects tab, make sure that Surface elevation using "Linear interpolation" is checked.

- In the modules tab, make sure that you have checked the LuaConsole
- Run any scenario and open the Scenario Editor.
- Press New
- Name the vessel however you want and select from the dropdown list: "Rect" if you want to flatten a rectangular area of "Ellipse" if you want an elliptical one.
- Make SURE that you have checked both Set camera and Set input focus and press "Create"

-Press "Location" and place the created vessel near the coordinates that you wish to flatten.
-Select Function from the top bar-menu (or press Ctrl-F4) and select Lua Console.
-In the Lua Console window type: run("flat")
-The Script will run and you will see instructions on screen about the keys and the flat area information.
-Watch the video to see a demonstration.
Notes:
In the beginning the tool has a size of only 1 meter. You will press the keys needed to adjust its size (shown on screen).
The actual flattening depends on the resolution of the elev tiles that are available in the area. Don't try to draw rectangles that are exactly the size of a runway, because most probably the elev tiles that you have won't support it. So unless you know what you are doing, it's best to draw a bigger area than the one you actually want to flatten.
The line with the information for the flattening gets appended (written at the end) of a file named "My_flat_file.flt" located in the Textures\((Name of body)\Flat folder.
(you can change the name of the file if you want by editing Line 2 in the Script\flat.lua file. You can even enter an existing .flt file. It will simply add a line at its end.)
In the Line 3 of the lua script, you can edit the falloff value. (default = 5, explanation in the same line of the lua file).
Give it a shot and let me know if it works for you.