There are a few things you need to remember when you use perspective in an image. (That is, when you want to work realistic. Any other type of work anything goes (just look at picasso and such artists).
Realisticly: You need to find the vanishing point on the horizon. This always is where YOUR eyes cross the horizon. How the rest of the image you create stand, sit, fly or fall, is related to this factor.
So, when you are sitting down, or laying on the ground, everything else towers above you, meaning, perspectives will be wide bottom, narrow top, but also, from the top to the horizon higest on the edges of the image, and lowest on the horizon.
When you use the viewpoint of a person standing, there will be a ballance between ground and sky. When you sit, the horizon will be more to the bottom of the "page".
I will illustrate this with a door in a landscape. (total nonsense I know, but you find doors easy and they usually are all the same hight (exept in a church).
The doors are about 7 foot high. The wall (lines) is about 10.5 foot high. Your eye level is indicated in the door and is the same in every door. So a part of the door is higher then your eye level (and so ABOVE the horizon)
Have fun with it.