[note: I added some commentaries in this font. First time readers can ignore those.]This topic and it's content has been copied over from YSPilots. It was written by TaskForce58 and the original can be found here
Some basics for the scenery editor:
Holding down shift and both left and right mouse button, and slide the mouse up and down: zoom in and out
shift and left mouse button: move the view around.
Now, start the editor. We are going to create a very simple scenery, with a large island and one runway, that's all.
Goto map->insert element. Select POLYGON on the drop down list. On the color palette (top right of window) select dark green. See the green box with the green lines on the screen? That's your plotting cursor. Drag it around, and hit enter. This will create the first point of the polygon. Drag the cursor around again, and hit enter again. Each time you hit enter you create the next point for the polygon. Once you have 5 or 6 points for your polygon, hit space. Now you have your island. Notice that you don't have to plot the last point of your polygon on the same location as the first one. Once you hit space the editor will close the polygon for you. Oh and the first time you create something in the editor, it will ask you if you want to create a new map. Just say yes.
{This is the common way of doing things in the editor. The Enter key to plot all the points, and Space to finalize any changes/additions.}
Next, the runway. We will create a east-west runway (i.e. Runway 09/27) with a rectangle. Creating a rectangle is a little different than a polygon. You have to specify 3 points. The first two defines the baseline of the rectangle. The third is the width.
{What will happen is that the rectangle will be aligned with one of the edges on the baseline you defined, then the editor will create the smallest rectangle that includes both the baseline and the third point you specified. The third point does not neccessary mean it is one of the corners of the rectangle, just that it will lie on the side opposite to the baseline.}
Zoom in until the blue grid just about covers the whole screen. Use map->insert element, and select RECTANGLE this time. On the color palette select dark grey. Drag the cursor around until it lines on the left edge of the blue grid. Take a look at the coordinate window. The first value (from the top) is the East-West coordinate, the second is the altitude (normally 0), the third is North-South. Now hit enter to create the first point, but don't drag the cursor around afterwards.
Take a note of the coordinates of the cursor. Since we want a runway that is 3200m long, add 3200 the the East-West coordinate (i.e. click in the box and type in the actual value), and click SET. This will move the cursor exactly 3200m due east of the first location. Now follows one of the little quirks of the editor. Since we clicked in the coordinate window to enter the value, you have to click on the main editor window again. However, we don't want to accidentally move the cursor around, so click on the window title bar of the main editor window to select it. Hit enter, and you have entered the second point of the rectangle.
{This is a more precise way of entering things, when you need to draw something with a specific dimension, such as runways. BTW 100 ft = 30.48m}
Once again look at the coordinate window, and this time add 42 to the North-South coordinate. Click set, select the main editor window, and hit enter. This will add the third point of the rectangle 42 meters due south of the first two. Hit space, and you should have a long thin rectangle in dark grey. This is your runway.
{HotelFox asked about a runway of 3200mx42m, hence the dimensions I used here.}
The third step of our simple scenery is to define the runway area. The method is almost identical to entering a rectangle. Select Edit->Insert->Rectangular Region. On the drop down list select 1 for runway. Now you need to enter a rectangle that is (roughly) identical in size and location as the grey rectangle we created to be the runway. You can use the precise coordinate method as we used for the runway, or you can just eyeball it. Once you are done you should have a blue rectangle surrounding where the runway is, with the tag "RGN ID=1 (Runway)" in the middle.
{The rectangle region is a very important element of YSFlight scenery. It is what defines a runway, taxiway, and viewpoints. Infact in our example you don't even have to draw that grey rectangle for the runway. You can just put a rectangle region down and set it as a runway and it will work. Of course a 10000ft grass strip in the middle of a lush green island 10 km wide is gonna make it very hard to find and land on!}
Goto File->Save FLD to save the scenery. Name it "myairport.fld" for our example here. Make sure you are saving it into YSFlight's scenery folder.
Last thing is to create a start position. Goto StartPosition->Insert. Drag the cursor to the western end of the runway, and hit space. You will be presented with a popup window. On the ID Name box, enter "RWY_09". Initial Speed should be 0. Landing Gear box should be checked. Throttle is 0 percent. Click OK. You have created a start position, but it is pointing north. Now select StartPosition->Rotate. The start position we just entered is now circled, with a thicker green arc beneath it. Drag the green arc around and you can rotate the start position. Keep draging the green arc until the long green dash line (the heading) is pointing towards the right (east) down the length of the runway, and hit space to confirm the change. Goto File->Save STP to save the startposition. Name it "myairport.stp"
{When you enter a start position that is on the ground double check the coordinate window, make sure the altitude (second box) is 0. If you want an inflight start position, then you can set the altitude to something other than 0, but make sure you have a reasonable initial speed, make the throttle something other than 0 percent, and uncheck the landing gear box.}
Now we have the actual scenery and the start position(s) done, we just have to let YSFlight know about it. In YSFlight's Scenery folder, use a text editor (such as notepad) to open the scenery.lst file. Add this line to the end:
MY_AIRPORT scenery/myairport.fld scenery/myairport.stp
and save the file.
Next time you start YSFlight, you should have a new scenery called MY_AIRPORT with only one start position, RWY_09.