Quick Tips for Using COLUMBUS

Deformation Analysis

Deformation Differences in Six Steps

COLUMBUS allows you to compare the coordinate results of subsequent adjustments. Using the approach described below, you can examine the movement of a station from one adjustment to another. A movement (also called a shift or difference) report can be written to a comma-delimited *.csv (Microsoft Excel) file, then imported into other third-party software packages.

This technique works well, because COLUMBUS tracks two types of coordinates:

• those that are known and in project memory;
• and those that have just been computed, but are not in project memory.

Note: Project memory is simply the memory space of COLUMBUS that persists from one activity to another, until either the active project is closed or you exit COLUMBUS.

Follow these steps to compare adjustments on the same stations, using two independent sets of observations made during May and August:

1. Adjust the network from May using COLUMBUS. After you are satisfied with your final adjustment, Keep the adjusted coordinates into memory, then save the contents of memory out to a COLUMBUS ASCII (Text) file by selecting the Save As option from the File menu.

2. Using a simple text editor (for example, Windows Notepad), load the file just created and remove all observations, leaving only the adjusted station coordinates.

3. From the File menu, select Open to load this modified file (without observations) back into COLUMBUS.

4. From the File menu, select Append to load the survey data from August. The May adjusted station coordinates will remain intact, since they were loaded first. Now you are ready to adjust the August observations.

5. Set up the generation of *.csv reporting by following the steps described in the Quick Tip, Generating comma-delimited compact reports for use in third-party software.

6. Perform repeated adjustments with the August data, but don't invoke the Keep option from the Adjusted Coordinates View (yet). For each adjustment you perform based on August observations, you can view the coordinate differences from the May adjustment by opening the Results | Coordinates | Coord Differences view. To save the coordinate differences to a comma-delimited *.csv file, select the Report option from this view.

For analysis of the August survey with a future survey, follow Steps 1 and 2 above using the results from the final August adjustment (in those steps).