Duplicate Traverse Marks: understanding the Pre-validation Report

Sometimes when an e-survey is captured into Landonline, multiple marks that should be a single mark are created on or near the same spatial location.

This is caused by not linking the new mark to the existing Landonline mark, and as a consequence, these duplicate marks can cause topological errors within Landonline.

When pre-validation is executed for a new e-survey, the business rule Y024 is used to test for adjacent marks. Marks found within a specified tolerance of a new captured mark are reported to the user for further investigation. The tolerance is currently set for all survey classes at two metres. The report helps the user identify any potential traverse mark duplications, or corruption of Geodetic Mark information.

The rule compares all traverse marks (i.e. non-boundary marks) on the new survey with all relevant and authoritative traverse marks in Landonline not connected into topology. Duplicate boundary marks are identified by missed mark functionality. Any marks on the survey that have found a potential duplicate mark(s) are listed in the report. The report lists 'Survey marks' and 'Landonline marks', along with any associated mark information that could alert the user to possible duplication.

Any marks listed must be investigated to confirm whether:

  1. the new mark should have been linked to the existing Landonline mark, or
  2. marks reported are correctly captured.

Example warning report for pre-validation:

Y024 - Warning: the following marks could possibly be duplicate occurrences of other marks already in Landonline:

IDSurvey MarkLOL MarkDistOrderLOL Mark Description
1001IS V DP 3011123IS V DP 30111230.026DN 0.3 m seal
1004OIT I DP 621245IT I DP 6212450.037iIT I DP shown out of position on DP 3004214


Note: The pre-validation report is best copied to Notepad and printed using a Courier font in order to maintain the columned format.