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Frequently Asked Questions
In this section, Best-Fit Computing answers Frequently Asked Questions (FAQs) about geodesy, surveying and our product,
COLUMBUS.
Click on the topic or question below to find out more.
Network Design
Network Adjustment
Coordinate Geometry (COGO)
Coordinate Transformation
1.
Network Design
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?
2.
Network Adjustment
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?
3.
Coordinate Geometry (COGO)
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?
4.
Coordinate Transformation
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?
We welcome your questions;
please contact us with yours!
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Network Adjustment and Coordinate Transformation
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