So I have a layered base field template with pro and college field markings. My template is at 1920x1080 pixels so it will scale correctly for my HD monitor. I look at pictures from as many angles of the stadium as I can find to get dimensions from the field and where the stairways go and such. I have found that ticket selling sites like SeatGeek have good section views and I use Google maps when I can to measure distances. Then its just a matter of making layers for the seat risers, seats, stairs, walls etc. For this stadium, it took about 15 hours. I have about 15 NFL ones done so far. Done a few college ones.