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Does Cognite Unit Catalog can support relative measure units ?

  • June 13, 2025
  • 1 reply
  • 57 views

Marwen TALEB
MVP

Hello, 

We currently have the need to support radioactivity timeseries that are measured with the gAPI unit. 

What is gAPI? 

API (American Petroleum Institute) units are commonly used in the oil industry to indicate natural radioactivity in geological formations, particularly using gamma ray logs.
gAPI stands for giga API units (1 gAPI = 10⁹ API units), but it’s often a confusion — in most cases, gAPI simply means “gamma API units”, not giga.
• In well logging, 1 API unit is a relative measure, not an absolute unit of radioactivity like Bq.

 

This makes gAPI very difficult to integrate to the CDF unit catalog (https://github.com/cognitedata/units-catalog). Since we cannot have an absolute conversion to an SI unit. This conversion depends on  calibration curve or lab measurement linking the gamma ray count in API units to disintegrations per second (Bq).

 

My question is: is there a way to support this in the unit catalog? Support of units without conversion to a SI unit?

 

It is very important to us that every timeseries is linked to unit in the CDF catalog and have a unit_external_id even though we will not use conversion for this particular unit.

 

Happy to discuss.

 

Thank you, 

 

 

1 reply

Everton Colling
Seasoned Practitioner
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  • Seasoned Practitioner
  • June 13, 2025

Hi ​@Marwen TALEB!

Cognite unit catalog is designed around the principle that each unit should have a deterministic conversion path to SI units. When we designed the catalog we identified that this approach covers the vast majority of industrial unit conversion requirements and ensures consistency across the platform. However, it doesn't accommodate specific units that require dynamic conversion factors like currencies or units that require context-dependent or calibration-based conversions, like gAPI.

I don’t know exactly the context in which you need to consume this time series data, but unfortunately for the time being you’ll have to implement some client side logic to handle unit conversion cases that don’t conform to the existing functionality provided in CDF. You could potentially store free text unit definition in time series and write some client side logic to handle the conversion as needed for these nonstandard units.

For a native solution, we can convert this question into a Product Idea and monitor interest from other CDF users. If this turns out to be a common challenge amongst our user base, we can consider an improvement to our catalog to accommodate these types of units. ​@Mithila Jayalath can you convert this into a Product Idea?