Adjustable iron plate for bridge decks is the flatness of a tool. Pitch method is the use of concrete slab on the measured surface segment by reading the paragraphs before and after the two instruments measure the straight line relative to the standard money angle or height difference, obtained by data processing straightness, flatness error of the value of an indirect measurement method measuring principle is to test a number of equally spaced cut-off line into gear, with the level or from the collimator, respectively, each measured block relative to the base of the tilt angle by measuring 1 "= 0.005/1000 into radians, multiplied by the concrete slab span, it reflects the span of two points relative to the benchmark measure the height difference. hi = (0.005/1000) Clai (mm) where C - Instrument division value ,("); L - concrete slab span, mm Ai - instrument reading frame height difference between the cumulative sum of the block and is measured relative to the measuring point reference height Hi, that Hi = hi pitch reflected in the measurement method exists as an imaginary straight line of ideal benchmarks to improve the measurement accuracy. 
 http://www.knzzlj.com/ztpt/ktxjb.html for cast iron plate flatness tools pitch is to use the bridge deck surface of the segment measured by the instrument to read two paragraphs before and after Compared to the standard straight-line measurement of the angle of inclination or money to a high degree of difference, obtained by data processing straightness, flatness error of the value of an indirect measurement method measuring principle is to test a number of equally spaced cut-off line into gear, with Level or from the collimator, each block were measured relative to the base of the tilt angle by measuring 1 "= 0.005/1000 into radians, multiplied by the concrete slab span, it reflects the span of two points relative to the height measurement reference difference. hi = (0.005/1000) Clai (mm) where C - Instrument division value ,("); L - concrete slab span, mm Ai - instrument readings, cell height difference between the cumulative sum of the block and that the measuring point relative to the benchmark measure the height Hi, that is, Hi = hi pitch measurement method embodied in the existence of a hypothetical ideal line as benchmarks to improve the measurement accuracy. 
 http://www.knzzlj.com/ztpt/ktxjb.html