Real-Time Deflection Monitoring
An automated total station watching continuously, alerting the moment something crosses a trigger.
Scope
This is a specialist capability and there are very few practices in New Zealand running it properly. We install an automated total station permanently on site. It observes a set of prisms continuously, recomputes its own position every cycle, compares each round against the baseline, and sends an alert the moment a reading crosses a threshold you agreed in advance. Nobody has to be watching a screen. If a prop deflects at 2am, somebody's phone goes off at 2am.
- Automated total station installed permanently, observing continuously
- Automatic alerts by email or SMS the moment a trigger level is crossed
- Live dashboard and movement plots, no waiting for the next report
- Resection against stable reference prisms every observation cycle
- Two-face observation and atmospheric correction on every round
- Deflection under load: propping, temporary works, bridges and crane bases
- Continuous monitoring of structures adjacent to excavation, piling and demolition
- Agreed green, amber and red thresholds with a named escalation path
- Full observation record, defensible if a claim ever lands
Most jobs do not need continuous observation, and we will tell you if yours does not. See scheduled survey monitoring.
Who it is for
Temporary works and propping
Watch the props while the load is on them, not afterwards. Continuous observation with alerts is the difference between a pause and an incident.
Deep excavation and piling
Neighbouring buildings, retaining systems and services monitored through the works, with a defensible record if a claim ever lands.
Bridges and load testing
Deflection under applied load, captured continuously through the test rather than at a handful of discrete points.
High-consequence works
Anywhere movement can develop faster than a reporting cycle, and the cost of finding out late is measured in more than money.
Setting up an automated total station
Design the scheme
We work out what needs watching, where the prisms go, and what movement actually matters. Prism positions are chosen for a clear line of sight and for structural relevance, since a target on something that cannot move tells you nothing.
Establish reference control
Reference prisms go on stable ground well outside the zone of influence. These are what everything else is measured against, and getting them far enough away is the single most common thing done badly on other people's schemes.
Install the instrument
The total station is mounted in a fixed, protected position with power and a 4G connection. Bracket, pillar or purpose-built housing depending on the site and how long it needs to survive there.
Set the observation cycle
The instrument works through the prism list automatically, on a cycle set to the risk. Every observation is taken on both faces, which cancels collimation and vertical index error, and atmospheric corrections for temperature and pressure are applied so the distances are honest.
Resection every epoch
Each cycle starts by re-observing the reference prisms and recomputing the instrument position. This is the part that matters: if the instrument itself settles or gets nudged, the resection absorbs it, so you see movement in the structure rather than movement in the tripod.
Trigger levels and alerts
Green, amber and red thresholds agreed before anything is switched on, with a named escalation path. Crossing amber sends an alert automatically, day or night.
Live data and reporting
Movement plots update as observations come in. Formal reports on whatever cycle you need, with the full observation record retained.
Frequently asked questions
What is real-time deflection monitoring?
An automated total station is installed permanently on site and observes a set of prisms on the structure continuously, cycling through them on a schedule. Each round is compared against the baseline, so movement is detected as it happens rather than at the next visit. If a reading crosses an agreed trigger level, the system sends an alert immediately.
How does the instrument know it has not moved itself?
Every observation cycle begins by re-observing reference prisms placed on stable ground outside the zone of influence, and recomputing the instrument's own position from them. Any settlement or disturbance of the instrument is absorbed by that resection, so it does not show up as false movement in your structure.
Why observe on two faces?
Taking each observation on both telescope faces and meaning the results cancels collimation error and vertical index error in the instrument. On a scheme chasing very small movements, systematic instrument error is exactly the thing that will fool you.
How accurate is it?
Achievable precision depends on range to the prism, network geometry, prism quality, how stable the reference points are and atmospheric conditions. Rather than quote a brochure figure, we model what is achievable for your specific setup and tell you before you commit, because a monitoring scheme that cannot resolve the movement you care about is worse than none.
Do I actually need real-time, or will scheduled monitoring do?
Most jobs do not need real-time, and we will say so. Scheduled monitoring costs a fraction as much and suits slow movement where a weekly or monthly reading is timely enough. Real-time earns its cost when movement can develop faster than your reporting cycle, or when an alarm needs to reach somebody within minutes.
What happens when a trigger is crossed?
An alert goes out automatically to the people named in the escalation plan, by email or SMS, without anyone needing to be logged in. What happens next is whatever you agreed at green, amber and red, which is why those conversations happen before the instrument is switched on.
How long does an installation take?
Design and prism installation is usually the longest part. Once the scheme is agreed, getting the instrument installed, powered, connected and observing is typically quick. We will give you a programme with the proposal.
Do you keep the raw observations?
Yes. The full observation record is retained, which matters if a dispute or claim ever turns on what was moving and when.
Need a surveyor?
Send the site address and what you need delivered.