I found this translation: "In order to assess the value of the adjacent plot, OPAK used the method of "land costs" . The basis for using this method is that the value of real property for commercial development depends on intended and permitted use in combination with the property's development and expected earnings potential.

Land costs are defined as the difference between the sales values of the fully-developed property less the total building costs including profit, but excluding costs of land, divided per square meter built-up area. Basement area is usually excluded, but if underground development constitute an important part of the development or has a high value, the underground area will be part of the calculation.
". Search for "tomtebelastning" + "land cost" and you'll get a Word file with the full text. But I would also check "land value" and "land price index".