In developing a real property appraisal, an appraiser must be aware of, understand, and correctly employ those recognized methods and techniques that are necessary to produce a credible appraisal.
— USPAP 2016-2017 Edition The Appraisal Foundation
 

Are the Solomon Calculators recognized methods or techniques?  

The Solomon Calculators use the Depreciated Cost method of developing adjustments for the Sales Comparison Approach.  Depreciated Cost is one of several techniques included in "The Appraisal of Real Estate" - Thirteenth Edition, on page 316.

 

depreciated cost page 2.jpg