Commercial Property Depreciation

[Jeffrey Mcintyre]

Hello,

I was reading a book on Cash-flow and came across a topic on depreciation.

I understand what it is and how to calculate it for a commercial property.. however I'm unsure how locate the value of the land a building sits on so i can determine how much of the Building can actually be depreciated...as per the book I'm reading..the land is worth about 15% and the building is only worth about 85%......so for instance, I can only depreciate 85% of a $1,000,000  commercial property over 39 years...can anyone tell me where I would find such information to determine the value of the land so i can accurately calculate the depreciation?