USER GUIDE - ADJUST FILE

The Adjust File page allows you to perform an adjustment directly from the contents of a data file. For users who prefer to set up and define all adjustment parameters within a data file, this is a compelling option.

Network Design

Network design works when the quality obtained in the field is as good or better than what you designed.

You can either perform an Adjustment of existing field data (the most common scenario) or evaluate the Design (Pre-Analysis) of a network that has not yet been measured.

Network design allows you to determine the statistical results you can obtain in the field—before you even make a measurement. By working with three variables, you can design a network that will help you minimize field costs, while achieving the quality standards specified for the project.

The three variables are:

1. Number of stations and their location (given by coordinates)
2. Types of measurements: GPS dX, dY, dZ, hor angles, directions, slope distances (chord), etc.
3. The expected standard deviation (or standard error) for each measurement type

Step-by-step

1. Tell Columbus the stations to use, along with their approximate coordinates.
2. Indicate the observations that will be observed at each station (including station names and observations). Since you have not measured the observations yet, you simply enter a number such as 1.0 for the observation value.
3. For each observation, provide the expected standard deviation that you expect to meet in the field—just like you would do for an adjustment.

As you can see, the data entry for Adjustment vs. Design is nearly identical. However, Design cannot compute the approximate coordinates, since you have provided no real observation values. Therefore, you must provide the approximate coordinates for each station (in 1D, 2D, or 3D, depending on the network type).

When you select an project file, all the usual network adjustment statistics will be computed for your review. These statistics are a function of the location of the stations (approx coords), the observation types used and the expected error of the observations. If the resulting statistics (distance errors, ALTA results, 2D error ellipses, etc.) don’t meet the project requirements, keep tweaking your design until they do.

For example, you may do one or more of the following to improve your design results:

1. Use more accurate total station, thereby allowing you to set your design standard deviations to smaller values.
2. Add GPS vectors to minimize network geometry issues.
3. Strengthen the geometry of a conventional network by avoiding small horizontal angles.
4. Add more observations to increase the number of cross-ties to other stations, thereby increasing redundancy.

Later, when you do the field work, if you set your stations at the designed locations, measure the designed observations and achieve the quality of the designed standard deviations, you are guaranteed to get a final adjustment that meets your project quality requirements (after removing any blundered observations).

Note: When using the Adjust by File feature (adjusting from a file), insert the following keyword near the top of the input file to indicate you are performing Network Design and not a Network Adjustment.

_ADJUST_DESIGN

Example network file

There are several example network files available on our website, found on the Sample Network Files page. Below is a complete input file for a Leveling Network. It is ready to load and run within the Adjust File page: