Frequently Asked Questions

1. Network Design
2. Network Adjustment
3. Coordinate Geometry (COGO)
4. Coordinate Transformation

• How "good" must the approximate geodetic coordinate positions be for effective Network Design (Pre-Analysis)?
  

• In COLUMBUS, can I assign a global standard deviation to each observation type without having to change each observation standard deviation individually?
  

• Why should I perform minimally constrained adjustments (one station fixed), before performing fully constrained adjustments (two or more stations fixed)?
  

• Since GPS baselines are based on the WGS 84 datum, how can I use them on my country's local datum?
  

• How can I fix the latitude or longitude of a station (but not both)?
  

• Can I combine terrestrial measurements (observations) with GPS and obtain high-quality results?
  

• What is the purpose of the Chi Square Test On Variance Factor? Where does the number generated come from?
  

• Why should I be concerned if the a posteriori variance factor is statistically different from 1.0 after performing a network adjustment? If I set the A Priori Network Variance Scaler in the OPTIONS - NETWORK OPTIONS - NET/OBS SCALERS dialog box to the a posteriori variance factor, then readjust, the new a posteriori variance factor goes to 1.0.
  

• What is the difference between a Fixed station and a Constrained station?
  

• What is the purpose of the Confidence Level setting? What is the difference between a Confidence Level setting of 0.95 and other values?
  

• Within the Residual Distribution histogram, what are the units for the Y-axis? What are the meaning of the values 0.1, 0.2, 0.3...?
  

• What are Height Confidence Intervals?
  

• What are "mark-to-mark" reductions?
  

• What is the difference between a corrected observation and an adjusted observation?
  

• Sometimes I am unable to change Options Settings in COLUMBUS; why?
  

• What is the difference between a 3D Local NEU (north, east, up) Inverse and a 3D ECEF (x, y, z) Inverse?

• When computing a 3D Astro Geodetic Inverse, how do the deflection of the vertical components (optionally provided for each geodetic station) affect the results?

• I was recently given over 150 stations with known NAD 83 State Plane coordinates. I need to transform these to NAD 83 UTM coordinates. How can I do this within COLUMBUS?

• I have just performed a network adjustment yielding 2D geodetic coordinates. Must I first keep these coordinates into the project in order to compute State Plane coordinates for each station?

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