Erroneous data vs unexpected data

In the world of monitoring and measurements, the words ‘erroneous’ and ‘unexpected’ are often used interchangeably.

However, each term has a very different meaning, and understanding which one most accurately describes anomalies in your data is vital to following the right process.

So, we’ve taken a look at what each means in relation to geotechnical monitoring and the steps which can be taken to understand or resolve surprising data.

Erroneous data

Erroneous data is information which is not an accurate representation of the current conditions you are measuring or monitoring.

Indications that the data you are gathering is erroneous can include:

– Large spikes in readings – which are often improbable or even physically impossible, for example readings many times greater than expected
– Intermittent data – where there are gaps in the readings being collected
– Sudden significant changes in data trends – not just spikes but sustained high or low readings

When using geotechnical monitoring equipment, there can be a number of broad causes, including:

– Incorrect installation of measurement equipment
– Damage to a sensor or cable
– Loose or intermittent connections
– Interference from other equipment, activists or even people

Unexpected data

Unexpected data is information which is a true and accurate measurement of current conditions – but outside of the range of the results that might be predicted.

Typical indications that data is unexpected – rather than erroneous – include:

– Repeated data – such as anomalies that begin to occur more frequently
– Sustained trends in the data – for example, suggesting a direction of movement in the ground conditions being monitored
– Changes during site works and other activity
– Variations that look to be driven by temperature, barometric or tidal changes

When using geotechnical monitoring equipment, there can be a number of broad causes, including:

– Unexpected ground conditions
– Incorrect modelling – meaning actual results deviate from those predicted
– Influence from other parameters or variables – such as adverse weather conditions

The relationship between erroneous and unexpected data

The relationship between the two forms of data is typically one way.

Unexpected data is often described as erroneous. As the reading is not as predicted, it must be incorrect!

This often results in push back to the contractor carrying out the monitoring or the manufacturer/supplier of the monitoring equipment. This is understandable given the potential ramifications of unexpected data.

However, the client, consultant, contractor and manufacturer can typically work together to understand the reasons driving the data. The conclusion is often that the sensors are performing correctly, a cause (or likely cause) can be identified and – rather than erroneous – the data is simply unexpected.

Steps to avoiding incorrectly labelling data as erroneous

Before concluding that the data is erroneous, there are a few troubleshooting activities which can be completed when conducting geotechnical monitoring, including:

Physical inspection – Check the sensors and their installation and look for any loose mountings, obvious movement, damaged cables or anything else that may impact the accuracy of readings.

Electrical inspection – Inspect the wiring of the sensors at the data acquisition units and any terminations. Look for any loose connections or damaged wiring. If nothing is obvious, you can also check the electrical resistance of sensors. For Geosense products, please consult the manual for specific troubleshooting details.

Review the data with site or design engineers – Sometimes, having a discussion with others can help identify reasons why the data might not be as expected. While modern models are very complex, they still rely on assumptions which can differ from the actual conditions found on site.

We’re here to help

If you’ve conducted these troubleshooting steps and your data is still appearing erroneous, we’re happy to discuss any potential causes and provide advice. Simply get in touch via our contact page and we’ll be in touch.

If you’d like support to increase skills across your team, our Geosense Academy offers training on how to get the very best from Geosense products and geotechnical monitoring. Find out more https://www.geosense.com/news/geosense-academy-helps-boost-uk-engineers-skills-in-geotechnical-instrumentation/