Joe Blecha

Tip of the Week #34 - The Power of the Comp Engine and the Point Derivation Report

Blog Post created by Joe Blecha on Apr 3, 2018

TBC works with raw survey data from your Trimble and third-party hardware, not just with *.CSV or X,Y,Z coordinates.  This means that TBC not only integrates data from different sources, like GNSS receivers, total stations, and levels, but also allows you to check, modify, and recompute the resulting coordinates from those different sources.

Let’s look at an example to illustrate TBC’s computation engine and the Point Derivation Report.  Check out Point 1000:

Zoomed in a bit more with some annotation detail, there are three measurements to Point 1000, a GNSS RTK shot from base station at Point 400, and two foresight total station measurements from Points 102 and RSCT_2.  

You can left-click on any of the colored vectors (blue for RTK, green for total station) and view the raw data properties, shown here:

Any of the text in BLUE color can be changed, for example changing the GNSS receiver measurement method or adjusting the observation’s prism type.  So many QA/QC options when working with the raw data, but I digress… on to the Point Derivation Report...

With Point 1000 selected in Plan View, right-click and select the Point Derivation Report from the context menu.  Alternatively, you can select, then right-click on Point 1000 within the Project Explorer and select the Point Derivation Report or with Point 1000 selected, click in the Reports drop-down from the ribbon and select Point Derivation Report.

An HTML-based report launches, which displays project, coordinate system, local site settings, and, alas, point derivation information!

All observations used to determine the resulting coordinate for Point 1000 show in the Point Derivation Report.  A closer look now shows the reported coordinate for Point 1000 and what observations TBC’s computation engine used to arrive at this coordinate, along with deltas, precisions, distance, and azimuth data.

For Point 1000, the Northing, Easting, and height values were computed using the RTK shot from Point 400 and the elevation is computed from the RSCT_2 resection station.  Armed with this information, you can now go back into the vector properties in TBC and enable or disable observations or toggle horizontal or vertical usage. Recompute the project using the F4 key and generate another Point Derivation Report to see how your manual edits or checks has modified the reported coordinate for Point 1000.  

The computation engine and its hierarchy and heuristics has an entire Power Hour session dedicated to it.  Check out the March 2016 Power Hour with Boris Skopljak and Troy Brown to learn how the computation engine calculates coordinates here:

TBC - Field to Finish with Confidence.