I have my tax bill and my insurance statement. I don't see anywhere that lists a "land value". I see appraised value and assessed value. Improvement value is what?

You may be able to go to the county property website and locate this information for the property.   If you cannot locate the information, taxpayers have used 20% of the purchase price as the land value (80% as the building)  or to be more conservative, you may wish to use 40% of the purchase price as land value, depending on the type of property you are renting.

Improvement value is the total value of the property, land and all structures, as shown on the tax bill. It's basically the amount on which your total property tax bill is assessed for the year.