Jul 20, 2021

ShapeArray versus In-Place Inclinometer Systems webinar Q&A

Tyler Morency
2 weeks ago

ShapeArray versus In-Place Inclinometer Systems webinar Q&A

Vertical and horizontal deformation measurements provide invaluable information to engineers and decision-makers, but with different types of inclinometer systems and advances in remote automated data collection, there are many factors to consider when determining which geotechnical instrument is right for your specific project’s monitoring requirements.

RST Instruments’ Matt Hartz and Measurand’s Matthew Miller presented a live webinar that offered an in-depth analysis and comparison between ShapeArrayTM and in-place inclinometer (IPI) systems.


Does altitude affect ShapeArray calibration?

No. Altitude variations could cause slight differences in the readings; however, ShapeArray systems are designed to autocorrect the readings in those situations.

When is it better to monitor for larger trends instead of precision? Which system works best for these objectives?

The technical specifications for both systems are relatively close, so you can expect similar behaviour when the equipment is installed with the same spatial resolution. (e.g., sensors every 50 cm).

However, if we make a comparison between the equipment at different spatial resolutions, that is, with ShapeArray sensors every 50 cm and IPI sensors every 1 m or higher, higher reading accuracy can be expected from the equipment with higher spatial resolution. On the other hand, even with a lower spatial resolution (i.e., greater spacing between sensors), IPI continues to show good results with adequate trend monitoring.

In general terms, it is important to take the following aspects into account when choosing a deformation monitoring system:

•          The technical specifications of your equipment

•          The system’s spatial resolution

Does the deepest ShapeArray sensor need to be placed in competent rock or foundation?

Yes, the deepest ShapeArray sensor must be placed in a competent foundation or a position where no movement has been previously identified (e.g., with existing inclinometer tubes from previous surveys). It is also important to highlight that ShapeArray measures relative displacement, so it is essential to have an initial reference point with no displacement.

What power source does ShapeArray use?

A ShapeArray in regular power mode typically requires a 12 V power source and about 1.8 mA of current per segment when connected to Campbell Scientific data loggers or sensemetrics’ Thread. In low power mode, typically used with wireless loggers, ShapeArray uses an 8 V power source and 0.4 mA per segment.

In summary, the power source for a single ShapeArray usually takes one of two forms:

  • Stationary batteries supplying the minimum 12 V and a current of 1.8 mA per segment.
  • Lithium batteries in cases where wireless data loggers such as DTSAA, Loadsensing, or Ackcio are used.

You can find more technical details for each solution at the following link: measurand.com/products/data-acquisition-systems.

How would ShapeArray be used and installed to monitor bridges?

For structural monitoring, ShapeArray is inserted into a tube with an inner diameter of 27 mm and fixed to the frame (usually with U-clamps near the equipment joints).

For bridge monitoring, ShapeArray can be installed vertically, horizontally, or even diagonally (at ±60° vertical and ±30° horizontal).

The equipment may be embedded in the piles of a bridge or, in the case of an existing structure, fixed on the outside. However, it is important to remember that ShapeArrays are relative-displacement monitoring equipment, so all their monitoring takes place in relation to a reference point that must be fixed or monitored externally with geodesic monitoring.

For sensors with separation greater than 5 m and wells 200 m deep, which system is most recommended?

For a case with a spatial resolution greater than 1.5 or 2 m, the recommended equipment would be an IPI system, since ShapeArray has a standard sensor spacing of 0.5 m for vertical applications and 1 m for horizontal applications. The maximum spacing between IPI sensors on the market is 3 m.

On the other hand, if you are looking for a higher spatial resolution over the entire 200 m length, ShapeArray might be a better option due to its simple installation and low cost.

How do different shapes of inclinometer casing affect the data? 

Different inclinometer casing shapes do not necessarily affect the quality of readings. However, the installation might require more care, since common practice and support documentation essentially focus on standard inclinometer tubes. 

That is, it is possible to use pipes with other cross-sections (e.g., hollow square steel tubes), but if the installation methodology is not properly adjusted, we can obtain results below the expected accuracy.

Still have questions?

  • 1993

    The Beginning

    Measurand is established in Fredericton, New Brunswick
  • 1994

    Bend sensor development

    Measurand develops and patents fiber optic bend and position sensors for the medical and automotive sectors

    U.S. Patent 5,321,257

  • 1995

    Canadian Space Agency

    Receives funding from the CSA to develop sensor technology that ultimately leads to invention of ShapeTape

    U.S. Patent 5,633,494

  • 1999

    Patent on fiber optic sensor

    Measurand receives patent for "Fiber Optic Bending and Positioning Sensor" issued June 29, 1999

    Canadian Patent 2,073,162

  • 2001

    ShapeTape & ShapeHand debut

    Measurand designs and develops innovative motion capture technology

    U.S. Patent 6,127,672, 6,563,107

  • 2002

    Measurand Attends the ICPMG

    First contact with the geotechnical sector at the International Conference on Physical Modelling in Geotechnics (ICPMG)
  • 2004

    ShapeArray

    Design patent application sent about a new product designed to meet the specific needs of the geotechnical industry

    U.S. Patent 6,127,672, 6,563,107

  • 2005-08

    ShapeWrap

    Measurand debuts ShapeWrap motion capture technology for the film and animation industry

    U.S. Patent 7,296,363

  • 2006

    Malibu installation

    ShapeAccelArray installed for ground monitoring for the first time​ in Malibu, CA

    Canadian Patent 2,472,421

  • 2007

    ShapeMRI

    Suite of instrumentation developed for motion capture within Magnetic Resonance Imaging (MRI) machines

    U.S. Patent 7,296,363

  • 2011

    SAAScan launched

    Built for rapid deployment and repeated use

    Canadian Patent 2,472,421

  • 2014

    SAAX launched

    Purpose-built for heavy-duty horizontal installation

    Canadian application 2,815,199 & 2,815,195

  • 2017

    SAAV launched

    The only geotechnical instrument with a patented cyclical installation method

    Cyclical Sensor Array, Canadian application 2,815,199 & 2,911,175