Watch the overview
79 seconds. A narrated explainer; the transcript is below. The written guide includes additional detail.
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- 0:00Every chainage in this example is numeric,
- 0:03but the sequence is one, two, one
- 0:05point five, then two point five kilometres.
- 0:08The pattern changes direction twice within one
- 0:11survey group. File order is not the
- 0:14same as the direction a vehicle travelled.
- 0:16A consistently descending survey can be legitimate.
- 0:20A lower number by itself is not
- 0:22proof that a vehicle went backwards. The
- 0:24cross-row check groups records by road, lane
- 0:27and measurement date where available. It examines
- 0:30changes in start-kilometre progression within that group,
- 0:33rather than mixing unrelated roads. The current
- 0:36ordering rule flags repeated direction changes: two
- 0:40or more reversals. It tolerates one reversal.
- 0:43This is a diagnostic for potentially mixed
- 0:46or scrambled records, not a blanket demand
- 0:49to sort every file. Project alignment can
- 0:52also compare chainage with geometric position where
- 0:55suitable reference data exists. Keep that spatial
- 0:58evidence separate from the row-order diagnostic. Review
- 1:01original run boundaries, lane attribution and acquisition
- 1:05records before changing data. The current direction
- 1:08analysis does not establish time-of-day travel direction.
- 1:12Resolve the cause and retain the evidence.
A valid number can be misplaced
Every chainage in this example is numeric, but the sequence is one, two, one point five, then two point five kilometres. The pattern changes direction twice within one survey group.
File order is not the same as the direction a vehicle travelled. A consistently descending survey can be legitimate. A lower number by itself is not proof that a vehicle went backwards.
Follow one road and lane
The cross-row check groups records by road, lane and measurement date where available. It examines changes in start-kilometre progression within that group, rather than mixing unrelated roads.
The current ordering rule flags repeated direction changes: two or more reversals. It tolerates one reversal. This is a diagnostic for potentially mixed or scrambled records, not a blanket demand to sort every file.
Identify the order before interpreting a reversal
Use a small fictional sequence of 2.000, 3.000 and 2.600 km to see why row order matters. The final decrease deserves investigation, but it could involve mixed runs, an export ordering problem or another source-context issue. A number sequence alone should not be treated as a video of vehicle travel.
Retain road, lane, date and any available time or run identifiers while reviewing the sequence. Compare the appropriate reference direction and the actual rule’s applicability. Do not sort away evidence of a problem merely to produce increasing kilometre values.
Use geometry as another test
Project alignment can also compare chainage with geometric position where suitable reference data exists. Keep that spatial evidence separate from the row-order diagnostic.
Review original run boundaries, lane attribution and acquisition records before changing data. The current direction analysis does not establish time-of-day travel direction. Resolve the cause and retain the evidence.
Sources and scope
This guide describes the platform workflow; it does not establish a requirement of a TMH manual. Platform review and certification are described in the product documentation.
Put it into practice
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