# How to determine the area size of a terrain for which I want to calculate its roughness

I want to calculate the wind speed on the ground for a specific location. In order to do so I will use the log wind profile. One of the input variables of this formula is the surface/terrain roughness.

How large should my terrain be if I want to obtain its roughness? Is there a rule of thumb?

The location is

``````latitude = 29.6615
longitude = -98.3933
``````

The location is on a golf green (https://ibb.co/h2tkHht)

The goal is to determine the drag force someone experiences when putting on a green. What do you recommend?

• Only the green?
• The whole golf course?
• 50m x 50m square around the green?
• 100m x 100m square?

I would assume that only the green is not viable because the green can be surrounded by trees (for different greens).

• Depends on your use case. Is this for fun? Then go with whatever you want. Is this for a use case of the golf course? Then cover the whole course plus 1 km. Is this for something related to renewable energies? At least +5 km.
– Erik
Commented Jul 19, 2022 at 9:42
• I want to determine the drag force someone experiences when putting on a green. So in this case, the coordinates are the center of that specific green Commented Jul 19, 2022 at 10:39