Roberts answer is very good as it takes actual sales figures over the last year to generate a very educated valuation, However I also agree that a land value will be in line with it's "best use", location, etc. If the average is what you are looking for, then the average is 5,614.13 at 13 acres, However... If you want to know exactly what your land is worth... Please contact me and I would love to walk the property and see exactly the location and what it could be used for!
Here is my contact information