scale factor
Scale factor is the ratio of turning a big model to a smaller model. To do scale factor first you must have the measurements. Once you have the measurements of the object you have you have to find a scale factor ratio. for exampl I have a building thats 25'x50'x40' and i pick a scale factor ratio for every 2' it's 1". once you have the scale factor ratio do the math and build your scale model.