The instrument works. But is it measuring accurately?
A surveying instrument may power on normally, aim, take measurements, and store data without necessarily maintaining the level of accuracy it should.
At METRICA’s Service Department, many of the issues identified during technical inspections have not previously been noticed by the operator.
Small measurement deviations, wear and tear on mechanical components, or sealing issues can develop gradually without any obvious signs.
Until a small deviation starts affecting measurement accuracy or wear develops into a failure.
That’s why preventive servicing is not only for equipment that has already developed a problem. Its purpose is to verify that the instrument is still performing as it should and to identify early any issues that could affect its accuracy, reliability, or availability on the next project.
Ask the Expert
We asked Nikos Alexandris, Service Manager at METRICA, which issues are most commonly found in surveying instruments that have gone without servicing for an extended period, and what operators should know before returning to the field.
At a Glance
An instrument may appear to be working normally while still exhibiting measurement deviations in angles or distances, the line of sight, the compensator, or the prism recognition and tracking system.
Regular servicing can identify such deviations, as well as mechanical wear or sealing issues, before they develop into failures or affect fieldwork.
Can a surveying instrument appear to work normally but still produce inaccurate measurements?
Yes.
An instrument operating normally does not, by itself, guarantee measurement accuracy.
Small measurement deviations can occur due to:
- angle or distance measurements,
- the line of sight,
- the compensator,
- the automatic prism recognition and tracking system.
The instrument may power on, aim, and take measurements without displaying an error message or any other obvious warning, even though its results may already be falling outside the expected accuracy range.
In a routine survey, a small deviation may go unnoticed.
However, in high-precision projects or when measuring over long distances, even a small deviation can have a significant impact on the final result.
What Problems Are Most Commonly Identified During Servicing?
When a surveying instrument has gone for an extended period without inspection or maintenance, the issues identified can affect both its measurement accuracy and mechanical condition.
Over time, lubricants in moving components gradually lose their effectiveness. Increased friction can accelerate wear in rotation and movement mechanisms, fine adjustment screws, and other mechanical components of the instrument.
At the same time, sealing components can deteriorate, reducing the instrument’s protection against dust and moisture.
Particular attention should also be given to the tribrach and optical components, while robotic instruments require additional checks of the automatic prism recognition and tracking system.
5 Common Problems We’ve Identified in Practice
During technical inspections in the Service Department, we have identified issues such as:
- Compensator deviation
The deviation may not be noticeable to the user but may require adjustment to restore the instrument’s accuracy and proper operation.
- Instrument axis misalignment
Such misalignment, particularly along the vertical axis, can occur following an impact or significant mechanical stress.
- Laser plummet misalignment
There may be a misalignment between the optical axis and the laser plummet, which is not always immediately apparent to the operator.
- Distance measurement deviation
During a technical inspection, discrepancies may be detected when measuring known distances, even though the instrument appears to be functioning normally.
- Moisture inside the instrument
Moisture can form a thin layer on the angle measurement circles and affect their accurate reading, without necessarily causing any visible external signs of damage.
These are typical cases where a technical inspection can identify an issue before it becomes apparent during fieldwork.
What Puts the Most Strain on Field Equipment?
Daily use gradually takes its toll on equipment, especially when it is operated in demanding conditions.
Factors that can put additional strain on an instrument include:
- continuous exposure to dust and moisture,
- working in rainy conditions,
- very high or very low temperatures,
- sudden temperature fluctuations,
- continuous use in demanding construction environments,
- vibration during transportation,
- impacts and accidental drops,
- long-term storage in unsuitable conditions.
The need for technical inspection, therefore, depends not only on how frequently an instrument is used, but also on the conditions in which it is used, transported, and stored.
How Often Should a Surveying Instrument Be Serviced?
Manufacturers generally recommend regular inspection and preventive maintenance of surveying equipment, typically on an annual basis.
Between scheduled service intervals, operators should regularly perform the instrument’s built-in “Check & Adjust” procedure.
This procedure is particularly important because:
- before carrying out high-precision work,
- after significant transportation or handling,
- after exposure to vibration,
- after an impact.
However, there are situations where a technical inspection should not wait until the next scheduled service.
When Is an Immediate Technical Inspection Needed?
An instrument should be sent for inspection when:
- it has been dropped or subjected to a significant impact,
- deviations are detected when measuring known points,
- significant discrepancies are observed between the two telescope positions,
- the instrument’s “Check & Adjust” procedure shows significant or unusual deviations,
- there are issues with prism recognition or tracking,
- the instrument’s rotation becomes difficult or behaves unusually,
- there are signs of moisture inside the instrument,
- repeated measurements at the same point produce inconsistent results.
In such cases, continuing to use the instrument without inspection can increase both the risk of inaccurate results and the likelihood of further damage.
What Does Preventive Maintenance of a Surveying Instrument Involve?
Preventive maintenance involves a comprehensive assessment of the instrument’s condition and performance.
Depending on the instrument and its specific requirements, this may include:
- an initial technical inspection,
- inspection and, where necessary, cleaning of the angle measurement circles,
- cleaning and lubrication of the focusing system, axes, and movement mechanisms,
- replacement of sealing gaskets,
- inspection and adjustment of the theodolite and distance measurement system,
- inspection of the tilt sensor, automatic targeting system, and motors,
- adjustment of the horizontal collimation and vertical circle index,
- installation of the latest software and application versions, where applicable,
- determination of the additive constant for the distance measurement system,
- final functional and accuracy check,
- cleaning of the instrument and its accessories,
- issuance of a Service Certificate.
The goal is not only to address existing issues, but also to identify early signs of wear that could develop into more serious problems over time.
What Can Be the Cost of Delaying Service?
The true cost of a breakdown is not always limited to the cost of repairing the equipment.
A single inaccurate measurement can result in:
- rework,
- having to send the field team back to the site,
- additional working hours,
- delays in project delivery.
Likewise, a minor mechanical issue left unaddressed can gradually develop into a more serious and costly failure.
There is an important distinction between preventive maintenance and repairing a breakdown:
Preventive maintenance can be planned. A breakdown or inaccurate measurement in the middle of a project cannot.
Regular servicing helps verify measurement accuracy, identify deviations and wear at an early stage, and reduce the risk of unexpected downtime.
It also helps protect the equipment and extend its service life.
Before Your Next Project, Check More Than Just the Battery
Before starting an important project, operators need to know that the instrument and its essential equipment are ready to meet the demands of the job.
Run the “Check & Adjust” procedure and inspect the tribrach, poles, and prisms.
If the instrument has been dropped or impacted, transported under demanding conditions, or is showing any unusual behavior, schedule a technical inspection before taking it back into the field.
For high-precision projects, or where required by the project specifications, also make sure that the measurement equipment has a valid calibration and the appropriate calibration certificates.
Because the right time to find out that your equipment needs servicing is before the project begins—not after measurements are already underway.
Frequently Asked Questions
Does an instrument that appears to work normally still need servicing?
Normal operation alone does not guarantee accuracy. Small deviations in measurements or individual systems can occur without any obvious warning signs.
How Often Should a Surveying Instrument Be Inspected?
As a general rule, annual inspection and preventive maintenance are recommended, with an additional check after significant transportation, vibration, or impact.
When Should I Not Wait Until the Next Scheduled Service?
If the instrument has been dropped or subjected to a significant impact, shows unusual deviations or inconsistent measurements, has signs of moisture, or develops issues with movement or prism tracking.
What Issues Can Be Identified During a Technical Inspection?
The inspection may identify issues such as deviations in the compensator, instrument axes, laser plummet, or distance measurements, as well as moisture ingress or mechanical wear.
Schedule Your Equipment Inspection
Annual servicing isn’t something you do because the instrument has failed.
It is carried out to verify that the instrument is still measuring accurately and to identify potential wear before it develops into a failure.
METRICA’s certified Service Department provides technical inspections and preventive maintenance for surveying equipment, helping ensure reliable operation and maintain the required level of accuracy in the field.
Has it been a year since your equipment was last inspected?
Contact our team to schedule an inspection before your next project by calling +30 210 281 5440 or by filling out the form below:
