Reduction
Slope, stadia, and level-run reductions, heights you cannot reach, curvature and refraction, and scale between grid and ground.
Turning field measurements into usable numbers: slope distance to horizontal, stadia, level runs and their closure, heights you cannot reach, curvature and refraction on long sights, EDM atmospheric and prism corrections, and the combined factor between grid and ground. It is for field crews and office staff reducing raw observations. Start with the slope reduction or the level run. Use ellipsoid height, not sea-level elevation, in the combined factor, and divide a grid area by the combined factor squared to get a ground area.
I want to correct an EDM distance for the air and the prism constant
- EDM atmospheric and prism corrections
Corrects a measured EDM distance for the air it traveled through (in ppm, entered or worked out from temperature, pressure, and humidity) and for the prism constant, each listed.
I want to reduce a slope distance to horizontal and vertical
- Slope distance to horizontal and vertical
Horizontal distance, vertical difference, and elevation difference from a slope distance and zenith angle, with two-face means and the curvature and refraction correction for long sights.
I want to reduce a stadia reading
- Stadia reduction
Horizontal distance, vertical difference, and elevation difference from a stadia rod interval and the sight's zenith angle.
I want to find the height of a tower or tree I cannot reach
- Height of an inaccessible object
The height of a tower, tree, or building you cannot reach, from zenith angles to its base and top and a horizontal distance, or from two stations in line with it.
I want to reduce a level run and check its closure
- Level run reduction and closure
Heights of instrument and elevations from a level book, the arithmetic check, and for a loop or a run between benchmarks, the misclosure, its allowable, and the adjusted elevations.
I want to correct a long sight for curvature and refraction
- Curvature and refraction correction
How much the earth's curve, less the bending of the line of sight, lowers a level sight over a distance, with the textbook coefficient for the refraction coefficient used.
I want to scale distances between grid and ground
- Combined scale factor (grid and ground)
The elevation factor and combined factor from a grid scale factor and height, and conversion of a distance between grid and ground.
Guides that use these tools
- GNSS control to OPUS to state plane: An OPUS position in ITRF2020 to NAD83(2011), then state plane coordinates, the orthometric height, and the combined factor for ground distances.