FAQ: Exported surfaces vary based on filter

Document created by David Kosakowski on Oct 5, 2020
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When I export a surface from WorksOS for a Trimble Earthworks Excavator system and apply Filters, I get noticeably different elevations.

  • Export #1. Date Range + Machine Design

  • Export #2. Date Range + Machine Design + Last Pass

Why is this?



Firstly, your reporting device is an excavator running Trimble Earthworks that appears to be using Minimum Elevation Mapping mode. 

When activated on a machine:

  • Minimum Elevation means Most recent Lowest Pass

  • Last Pass means Last pass

WorksOS records all data from the machine when either mode is activated; different rules are applied automatically when we recognize what mode you are in. These rules are the same behavior as the screen on the Earthworks EC520 display, so the operator and the person in the office see the same thing by default.

  • Export #1 follows the Minimum Elevation Mapping Rules and produces a surface of the most recent Lowest Pass, i.e., the most recent lowest bit of data in each of the cells.

  • Export #2 overrides the Minimum Elevation Mapping Rules and goes straight to the Last Pass, i.e.,  the last bit of data in each of the cells.

Applying this filter and not the other when exporting will produce different elevations based on the rules being applied. You can confirm this by using the DDV tool and analyzing all the passes in a cell where the elevation changes between the two different export types. The differences I saw were between the lowest pass in the cell and the last pass in the cell.

If you want to only see the Lowest Pass data for an excavator do not apply the Last Pass Elevation as this is a 'hard coded' filter that will supersede all other logic.

Note:  if this was a GCS Machine or not in Minimum Elevation mode, then applying the Last Pass Filter or not would not make a difference as the default is always Last Pass; the answer would be the same.