An inclinometer is one of the most established instruments used in geotechnical engineering to monitor ground and structural movement.

Engineers use inclinometers to track lateral deformation within slopes, embankments, retaining structures, foundations, and other assets over time. By measuring changes with depth, inclinometer systems can help identify developing zones of movement that may not yet be apparent from surface observations alone.

If you’re evaluating monitoring options for a mine, tailings facility, tunnel, dam, or slope, inclinometers are likely to be part of the conversation.

This guide explains what inclinometers measure, how they work, where they’re commonly deployed, their limitations, and how Distributed Fibre Optic Sensing (DFOS) can complement conventional inclinometer monitoring.

What Is an Inclinometer?

An inclinometer is a geotechnical instrument used to measure tilt and derive lateral displacement within the ground or a structure.

In a conventional borehole system, a grooved casing is installed within a borehole. A wheeled inclinometer probe travels through the casing and measures its inclination relative to gravity at defined depth intervals.

Successive measurements are compared with a baseline survey to determine how the casing has changed position over time.

By accumulating these changes along the borehole, engineers can develop a displacement-versus-depth profile showing where lateral deformation is occurring.

This depth-resolved information is one of the main reasons inclinometers are widely used in geotechnical monitoring.

Why Is Inclinometer Monitoring Important?

Ground deformation can develop progressively before significant surface expression occurs.

Regular inclinometer measurements allow engineers to identify changing displacement patterns and evaluate whether movement is stable, continuing, or accelerating.

Measurements can also be compared with other site information, such as:

• Rainfall
• Pore-water pressure
• Excavation stages
• Construction activity
• Loading
• Groundwater conditions

This information can support decisions about additional investigation, drainage, construction sequencing, ground support, access restrictions, or other risk-management measures.

For high-consequence assets such as tailings storage facilities, dams, and major slopes, inclinometer data often forms one component of a broader instrumentation and monitoring program.

How Does an Inclinometer Work?

A conventional borehole inclinometer uses a probe equipped with sensors and guide wheels.

The wheels follow longitudinal grooves within the inclinometer casing, allowing measurements to be repeated along consistent measurement axes.

As the probe moves through the casing, internal sensors—commonly accelerometer-based—measure inclination relative to gravity at defined intervals, often every 0.5 or 1 metre depending on the system and monitoring program.

The measured inclination is used to calculate incremental lateral displacement.

By accumulating those measurements over the length of the casing and comparing successive surveys with a baseline, engineers can develop a displacement profile showing how movement varies with depth.

A localized change in the displacement profile may indicate a zone of concentrated shear or deformation.

Interpretation should consider installation quality, casing behaviour, measurement repeatability, geology, and other monitoring information rather than assuming every change represents a discrete failure surface.

Key Components of an Inclinometer System

Inclinometer Probe: The sensing unit that travels through the casing and measures inclination.

Grooved Casing: Typically plastic casing with longitudinal grooves that guide the probe and deform with the surrounding ground or structure.

Readout Unit: A portable device used to collect, display, and store measurements during manual surveys.

Data Logger: Used with automated or in-place systems to record measurements without requiring repeated manual surveys.

Monitoring Software: Processes measurements into displacement profiles, trend plots, and other information that engineers can use for interpretation.

Common Applications of Inclinometers

Inclinometers are particularly useful where engineers need to understand not only whether movement is occurring, but how lateral deformation varies with depth.

Geotechnical Monitoring

Inclinometers are commonly combined with piezometers, settlement monitoring, survey measurements, and other instrumentation.

Together, these technologies provide information about deformation, groundwater conditions, settlement, and other geotechnical processes.

Slope Stability Monitoring

Borehole inclinometers are widely used to monitor slope deformation.

Changes in the displacement profile can help engineers identify zones where shear deformation is concentrating and estimate the depth of developing movement.

This can provide important subsurface information that complements surface technologies such as prisms, GNSS, LiDAR, radar, and InSAR.

Mining Operations

Open-pit walls and underground excavations can experience deformation as mining changes the geometry and stress state of the surrounding rock mass.

Inclinometers can be used to monitor lateral deformation within appropriately instrumented boreholes or structures.

Their measurements can complement:

• Microseismic monitoring
• Extensometers
• Convergence monitoring
• Radar
• Survey systems
• Distributed fibre-optic sensing

Tailings Storage Facilities

Inclinometers are commonly incorporated into instrumentation programs for tailings storage facilities.

Depending on facility design and site conditions, they may be installed within embankments, foundations, abutments, or other areas where lateral deformation needs to be monitored.

They are generally interpreted alongside instruments such as piezometers, survey systems, seepage monitoring, and other geotechnical observations.

Dams and Embankments

Inclinometers can monitor lateral deformation within dams, embankments, foundations, and abutments throughout construction and operation.

Monitoring can be particularly important during periods when loading or hydraulic conditions are changing.

Tunnels and Excavations

Tunnelling and deep excavation alter the stress state of the surrounding ground.

Inclinometers installed in nearby boreholes or retaining structures can help engineers monitor lateral ground response and assess whether deformation is developing as expected.

Retaining Walls and Foundations

Inclinometers can be installed within or adjacent to retaining walls, sheet piles, diaphragm walls, and deep foundations.

Measurements help engineers understand lateral movement and evaluate how the structure is responding to excavation, loading, and support conditions.

Bridges, Railways, and Critical Infrastructure

Inclinometers may also be used for long-term monitoring of bridge approaches, embankments, foundations, transportation corridors, and other critical infrastructure.

Measurements can contribute to asset-management programs by identifying developing lateral deformation over time.

Types of Inclinometers

Instrument selection depends on the monitoring objective, required measurement frequency, project duration, accessibility, and expected rate of movement.

Manual Borehole Inclinometer

In a conventional manual system, a technician moves a portable probe through the casing at defined intervals and records measurements at each depth.

Surveys may be conducted weekly, monthly, or according to construction stages and site conditions.

Manual systems can be cost-effective where periodic measurements provide sufficient temporal coverage.

In-Place Inclinometer (IPI)

In-place inclinometers use sensors installed permanently at selected depths or along sections of a borehole.

Measurements can be collected automatically through a data logger, allowing much more frequent monitoring than manual surveys.

IPIs can be particularly useful where conditions may change rapidly or site access is difficult.

MEMS Inclinometer

Micro-Electro-Mechanical Systems (MEMS) accelerometers are widely used in modern inclinometer and tilt-monitoring systems.

Their compact size, low power requirements, digital integration, and suitability for automated monitoring make them useful for in-place inclinometer arrays and other geotechnical applications.

Measurement performance depends on the specific sensor, calibration, temperature stability, installation, and system design.

Digital Inclinometer

Digital inclinometer systems provide measurements in digital form, simplifying acquisition, storage, processing, and integration with monitoring platforms.

Digital acquisition can reduce manual transcription requirements and support automated processing and reporting.

Benefits of Using an Inclinometer

Inclinometers offer several important advantages:

• Subsurface deformation monitoring: Provides information about lateral movement below the ground surface.
• Depth-resolved measurements: Helps identify where deformation is concentrated along an instrumented borehole.
• Trend monitoring: Successive measurements show whether displacement is stable, continuing, or accelerating.
• Engineering decision support: Measurements can support geotechnical assessment and operational decisions.
• Long-term monitoring: Properly installed systems can provide measurements over extended periods.
• Integration with other instruments: Inclinometer data can be interpreted alongside pore-pressure, survey, seismic, and other geotechnical information.

Inclinometers can contribute to early identification of changing ground conditions, but they should not be described as guaranteeing advance warning of slope or structural failure.

Limitations of Traditional Inclinometers

Inclinometers provide valuable measurements, but they also have limitations.

A borehole inclinometer measures deformation along the instrumented casing. It does not provide continuous coverage across an entire slope, embankment, or mine.

As a result, monitoring performance depends heavily on borehole location.

Movement occurring outside the instrumented locations may not be directly captured.

Other limitations can include:

• Manual systems provide measurements only when surveys are conducted.
• Automated systems still provide coverage only at their installed locations.
• Large monitoring areas may require multiple boreholes.
• Casing deformation can eventually make manual probe access difficult or impossible.
• Large shear displacement can damage or shear the casing.
• Installation quality can affect measurement performance.
• Monitoring remote or hazardous areas can increase access and maintenance requirements.

These limitations do not reduce the value of inclinometers. Instead, they explain why high-consequence monitoring programs often combine them with technologies that provide broader spatial coverage.

How Distributed Fibre Optic Sensing (DFOS) Complements Inclinometer Monitoring

Distributed Fibre Optic Sensing can complement point and borehole instrumentation by providing spatially distributed measurements along installed optical fibre.

Rather than collecting measurements only from individual boreholes, DFOS can provide measurements at many locations along a fibre route.

Different DFOS technologies provide different types of information:

• Distributed Strain Sensing (DSS) measures static or quasi-static strain changes along appropriately coupled fibre.
• Distributed Acoustic Sensing (DAS) measures dynamic strain and vibration.
• Distributed Temperature Sensing (DTS) measures temperature.

This distinction is important when comparing DFOS with inclinometers.

An inclinometer provides a lateral displacement profile within a particular borehole. DSS provides distributed strain measurements along the installed sensing fibre.

These are related but different physical measurements.

Strain measurements should not automatically be interpreted as direct ground displacement without considering cable installation, mechanical coupling, geometry, temperature effects, and site conditions.

Inclinometers and DFOS: Complementary Technologies

The two technologies can provide complementary information.

Inclinometers provide:

• Lateral displacement profiles
• Measurements at instrumented boreholes
• Established geotechnical interpretation methods
• Detailed information at selected locations

DFOS can provide:

• Dense spatial measurements along installed fibre
• Long sensing routes
• Continuous or repeated data acquisition
• Dynamic strain and vibration measurements with DAS
• Static or quasi-static strain measurements with DSS
• Additional spatial information between conventional monitoring locations

For large slopes, tailings facilities, mines, and infrastructure corridors, combining distributed sensing with conventional instrumentation can provide a more complete monitoring picture than either technology alone.

How to Choose the Right Ground Movement Monitoring Solution

The appropriate monitoring strategy depends on the physical process being monitored and the decisions the data needs to support.

Important considerations include:

• Spatial scale: A localized retaining structure may require only a small number of conventional instruments, while a large slope, mine, or tailings facility may benefit from broader distributed coverage.
• Expected rate of movement: Slowly developing deformation may be adequately monitored using periodic surveys, while rapidly changing conditions may require automated or continuous acquisition.
• Site access: Remote or hazardous locations may benefit from automated monitoring that reduces routine field access.
• Measurement required: Displacement, strain, pore pressure, vibration, temperature, and surface deformation are different parameters and may require different instruments.
• Monitoring lifecycle: Long-term projects should consider maintenance, accessibility, system durability, data management, and future expansion.
• Risk profile: Monitoring frequency and instrumentation density should reflect the consequences and expected mechanisms of failure.
• Regulatory requirements: Tailings facilities, dams, mines, and other regulated assets may have specific monitoring and reporting requirements depending on jurisdiction and applicable standards.

In many applications, the appropriate answer is not choosing between inclinometers and distributed sensing.

It is designing an integrated monitoring system in which each technology measures the parameters it is best suited to observe.

Why Choose Sintela for Advanced Ground Movement Monitoring?

Sintela specializes in Distributed Fibre Optic Sensing for mining, geotechnical, and critical infrastructure applications.

Distributed Monitoring with Sintela’s DFOS Technology

Sintela’s distributed sensing technology can use appropriately installed optical fibre to provide measurements across long sensing routes.

Depending on the sensing modality, system configuration, fibre characteristics, and installation, DFOS can provide dynamic strain, vibration, static or quasi-static strain, or temperature information.

Existing optical fibre may also be suitable for some distributed sensing applications.

However, existing fibre should be evaluated for factors such as:

• Cable construction
• Optical condition
• Route
• Accessibility
• Mechanical coupling
• Available fibre
• Required sensing performance

For quantitative ground-strain monitoring in particular, effective mechanical coupling between the sensing cable and the monitored ground or structure is essential.

Complementing Existing Geotechnical Instrumentation

Sintela’s DFOS solutions can complement conventional geotechnical technologies including:

• Inclinometers
• Piezometers
• Extensometers
• GNSS
• Prism monitoring
• Radar
• LiDAR
• InSAR
• Microseismic systems

The objective is not to replace established instrumentation, but to add distributed measurements where greater spatial coverage can improve understanding of changing conditions.

Talk to Sintela About Your Monitoring Requirements

If you’re evaluating inclinometers, distributed fibre-optic sensing, or an integrated monitoring approach, Sintela can help assess the sensing requirements, fibre infrastructure, site conditions, and monitoring objectives for your application.

Frequently Asked Questions

What is an inclinometer used for?

An inclinometer is used to monitor lateral deformation within the ground or structures.

Common applications include slopes, embankments, retaining walls, mines, dams, tailings facilities, excavations, and foundations.

What does an inclinometer measure?

A conventional borehole inclinometer directly measures the inclination of the casing relative to gravity at defined depth intervals.

These measurements are used to calculate changes in lateral displacement along the borehole.

How does a borehole inclinometer work?

A wheeled probe travels through grooves in casing installed within a borehole.

The probe measures inclination at defined intervals. Successive surveys are compared with a baseline to determine changes in the casing profile and calculate lateral displacement with depth.

What industries use inclinometers?

Inclinometers are widely used across:

• Mining
• Geotechnical engineering
• Civil engineering
• Tailings management
• Dam monitoring
• Tunnelling
• Transportation infrastructure
• Construction

What is the difference between an inclinometer and a tilt sensor?

The terminology can overlap depending on the product and application.

A borehole inclinometer is commonly used to develop a displacement profile along the depth of an instrumented casing.

A tilt sensor or tiltmeter typically measures angular change at a particular location on a structure, surface, or other monitored point.

What is the difference between an inclinometer and a piezometer?

An inclinometer provides information about deformation, while a piezometer measures pore-water pressure or hydraulic head.

The two are frequently used together because groundwater and pore-pressure conditions can influence geotechnical behaviour.

How accurate are inclinometers?

Inclinometer performance depends on the instrument type, sensor specification, probe repeatability, casing installation, survey procedure, temperature, calibration, casing condition, and data-processing method.

Rather than applying one universal accuracy figure to all inclinometers, performance should be evaluated using the specifications and field conditions of the particular monitoring system.

Can inclinometers be used for landslide monitoring?

Yes.

Borehole inclinometers are widely used for landslide and slope monitoring because they provide information about lateral deformation with depth.

This can help engineers identify zones where movement is concentrating and complement surface-monitoring technologies.

What are the limitations of traditional inclinometers?

Traditional inclinometers only provide measurements along instrumented boreholes.

Manual systems also provide measurements only at the times when surveys are conducted.

Additional limitations can include casing damage during large deformation, access requirements, installation costs, and limited spatial coverage across large sites.

How does Distributed Fibre Optic Sensing complement inclinometer monitoring?

DFOS provides spatially distributed measurements along installed optical fibre, while inclinometers provide lateral displacement profiles at specific instrumented boreholes.

DSS can monitor static or quasi-static strain, while DAS can monitor dynamic strain and vibration.

Together, these technologies can provide complementary information about how conditions are changing across an asset.

Can existing fibre be used for DFOS ground monitoring?

Potentially.

Existing fibre can be suitable for some distributed sensing applications, particularly certain DAS applications, but performance depends on the cable, installation, coupling, route, optical condition, and monitoring objective.

For quantitative strain monitoring, appropriate mechanical coupling between the fibre and the monitored ground or structure is particularly important.

Can ONYX™ replace an inclinometer?

Not directly.

An inclinometer and a DAS system measure different physical quantities.

An inclinometer provides lateral displacement information within an instrumented borehole, while Sintela’s ONYX™ DAS technology measures dynamic strain or vibration along suitable optical fibre.

Depending on the monitoring objective, ONYX™ can complement inclinometer networks by providing distributed dynamic information across longer sensing routes.

Where static or quasi-static distributed strain is required, an appropriate DSS technology can be incorporated into the broader DFOS monitoring strategy.