LOCATE RECORDS
A locate produces two things. Marks on the ground, which are gone in a few weeks. And a record, which has to last for years.
Most locate records answer one question: was the locate done? The question that gets asked after a strike is a different one: was the line where the marks said? This page is about the gap between those two, and what it takes to close it.
A closed ticket is asserted, not proven
A typical locate record today holds a ticket number, a completion time, a sketch showing roughly where the lines run, and a photo of the marks.
All of that is the locator's account of the job. It's usually right. But nothing in it can be checked by anyone who wasn't there. And because every paper record looks equally complete, nobody can tell the thin ones from the solid ones.
Nobody audits the gaps, because paper makes the gaps invisible.
The locator finds the line. The record has to say where.
A locator is a good instrument. It finds the line, tells you how strong the signal is and roughly how deep.
The record's job is the part after: writing down exactly where that reading was taken. That position is only as good as the receiver behind it.
Position error against the tolerance zone
This is the part that rarely gets talked about.
Tolerance zones are set by state law, commonly 18 inches (46 cm) either side of the mark and wider in some states (PHMSA state law summaries). Here's roughly what different kinds of GPS deliver, with the source for each:
| Positioning | Typical horizontal error |
|---|---|
| Phone or tablet GPS, no corrections | About 16 ft (4.9 m) under open sky, worse under trees (GPS.gov) |
| SBAS or DGPS | 3 to 7 ft (1 to 2 m) (FAA WAAS performance reports) |
| RTK, fixed | about ½ to 1¼ in (1 to 3 cm), per receiver manufacturer specifications |
When the position error is bigger than the tolerance zone, you haven't recorded where the line is. You've recorded roughly which yard it's in. Two locates of the same line can land six feet (1.8 m) apart on a map, and neither record will tell you which one is wrong.
At RTK accuracy the position stops being the weak link. What's left is the locator's reading itself. That's where the uncertainty belongs, because it's something the locator can see and explain.
PUC Services in Sault Ste. Marie deployed TerraFlow to connect its crews' RTK receivers to ArcGIS Online. Esri Canada reports PUC's positioning error fell from 10 to 16 feet (3 to 5 m) to about an inch (2.54 cm) (Esri Canada, March 2026).
The standard the industry already wrote
Subsurface utility engineering worked this out years ago. ASCE/UESI/CI 38-22 sorts utility information into quality levels:
| Level | How it's established | What you get |
|---|---|---|
| QL-D | Records and memory | Unverified |
| QL-C | Surface features surveyed and matched to records | Reconciled records |
| QL-B | Surface geophysics: EM locators, GPR | Interpreted position tied to the survey datum, 0.2 ft (60 mm) horizontal |
| QL-A | Exposed by vacuum excavation | 0.2 ft (60 mm) horizontal, 0.1 ft (30 mm) vertical |
Look at what sits at QL-B. The electromagnetic locator in your crew's hands.
An RTK receiver is specified by its manufacturer well inside the QL-B tolerance. So the locate your crew already does can produce a position good enough for the standard engineers use. It just has to be recorded properly. Whether a particular job is a QL-B deliverable depends on the survey method and the engineer responsible, not the software.
What a complete locate record contains
Six groups of information, captured while the locate happens rather than rebuilt afterwards.
Position. Coordinates for every located point. The GNSS fix type (RTK fixed, RTK float, DGPS, autonomous). The horizontal and vertical accuracy the receiver reported at that moment. The correction source.
Depth and method. The depth reading from the locator, tied to the point it was read at. The locate method: direct connect, induction, passive. The frequency and the signal strength.
Classification. Utility type and subtype. Material and diameter where they're known. The ticket number.
Who and when. The locator. A timestamp for each measurement, not just one for the ticket. The locator and receiver models used.
The sketch. Drawn to scale, in place, with the line paths and reference points. Photos tied to where they were taken.
The history. What was captured, when it synced, and whether anything changed after.
We'll send the full field list on request: contact@terraflow.ca
The record never claims more than the hardware delivered
Every point TerraFlow captures stores the conditions it was measured under. RTK fixed or float. The correction source. The accuracy the receiver reported at that second.
So a point captured under heavy canopy at 12 inches (30 cm) says so. A point captured RTK fixed at under an inch (2.5 cm) says so.
That honesty is what makes the record worth something. Anyone reading it later can see what was measured and how confident the measurement was. No form filled in at the end of the day can do that.
One is a memory. The other is a measurement.
After a strike, a paper record says the locator was there and marked the ground.
A structured record says, for example, that the gas main was found at 36 inches (91 cm), at these coordinates, by direct connect at 82% signal, at 12:47 on March 14, by this locator, with the receiver reporting RTK fixed.
The first is a recollection. The second is a measurement anyone can check.
Catch it on site, not three weeks later
A structured record syncs to the office as soon as the tablet has signal. So the office can see a locate while the crew is still standing on it.
A missing depth, a point with a poor fix, a line that stops short of the dig area: all of it is visible while the truck is still there. Fix it on site, or explain it for the life of the claim.
What piles up over time
One record describes one locate.
A year of them across a territory tells you things nobody knows today. Which crews document completely. Which corridors keep producing re-locates. Where the lines keep turning up somewhere other than where the utility's maps put them.
Every locate either confirms what the records say is underground or corrects it. Keep them structured and, after a few years, you have a picture of the subsurface built entirely from work that was happening anyway.
Who owns the records
Not us. TerraFlow doesn't own the records captured in it. How contractors and the operators they work for share records is between them.
How TerraFlow produces it
Utility mapping is the locating capability in TerraFlow Mobile. Your crew connects the locator and the GPS receiver they already carry. They locate the way they always have. The record builds as they go.
No forms to fill in afterwards. The record exists because they did the locate.
Try it on one truck Utility mapping · Supported locators and receivers