Network Design FAQs

The answer depends on the size of your network; more specifically, the length of each network leg. The approximate coordinates must be accurate enough to reflect the geometry on the ground. Good network geometry is critical to good adjustments and effective outlier detection. For network design, you must provide three things: the proposed network geometry; the types and frequency of observations; and the expected precision with which you expect to measure these observations. The approximate coordinates will satisfy the first requirement.

For example: You occupy Station A and measure a chord distance to Station B. If the stations are said to be only 100.0 meters apart in design (based on the approximate coordinates you have provided), then an expected precision (or standard deviation) of 0.05m may look OK in design, but would be considered unacceptable (1:2000) for a high-accuracy survey. This blunder would show up in network adjustment. On the other hand, if the two stations were actually 10,000.00 meters apart (1:200000) and you represented them as such in design, your future adjustment will likely deliver the expected results you modelled during design. This same logic can be applied to all observation types.

In general, the closer the three components are (network geometry, types and frequency of observations, and expected precisions of these observations) to what will ultimately be measured in the field, the better your resulting field work will match your design results.

Yes! COLUMBUS was developed to simplify these types of what-if analyses. Simply enter the OPTIONS - NETWORK OPTIONS - DEFAULT OBS SDs dialog box and set the standard deviation for all applicable observation types to a non-zero value. Changes only apply during network design or adjustment. They do not change your data within the current project. For azimuths, zeniths, bearings, directions and horizontal angles, the units are gons or seconds. For all others, the units are the current linear units.

Look in Quick Tips for more information on Network Design.