How is city sales study done?

Ron Wootters of Lambertville
    Thanks to the article Oct. 16 by Mr. Carmosino, Lambertville tax assessor, I think I now understand the assessment and tax process.
   The assessments are the base at $1.63 per $100. If property assessment is $100,000, taxes equal $1,630.
   If property assessment goes up to $125,000, taxes equal $2,037.50.
   In short, don’t raise the bridge, lower the water.
   I’m still not clear about how the Lambertville sales study is conducted?
Ron Wootters
Lambertville