You are building a small shed. you want to describe the area of the ground the shed will cover. which type of drawing, isometric or orthographic, would best represent the area?

Isometric is handy to see how it looks in 3D. You look down at the object from an elevated angle. Isometric drawings are done in a way to give the illusion it is three dimensional. The grid type is a series of triangles. 

An orthographic drawing is the object broken down into three parts: front view, side view, top view. Each of which are 2D. These three aspects help you visualize how they come together to form the 3D view. The orthographic aspect is also to help determine area, surface area, linear dimensions, etc. 

Since we want the area of the ground covered, it's best to go with an orthographic view. Specifically the top view. This is a birds-eye view looking straight down at the object. 

Orthographic is best

Side Note: CAD drawings often have the isometric and orthographic drawings done together to help better visualize the 3D object.