> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/data-api-sdk/data-model-fields-and-units.md).

# Data model, fields and units

Common questions about data model, fields and units.

## Articles

{% content-ref url="/pages/jmat0zSZSXXdRVh5pDeG" %}
[Why are so many data fields null?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/null-fields-are-provider-dependent.md)
{% endcontent-ref %}

{% content-ref url="/pages/icUqXcNrjjDrsK4XQHfG" %}
[Where do Garmin VO2 max and sleep score appear?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/garmin-metric-locations-in-data-model.md)
{% endcontent-ref %}

{% content-ref url="/pages/fmcyk6nk0Wz2ieRbWGWb" %}
[Where do I find field definitions and enum values?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/field-definitions-and-enum-lookup.md)
{% endcontent-ref %}

{% content-ref url="/pages/8AFjJFy36G5H5fQyUxWJ" %}
[Is the meal timestamp consumed time or logged time?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/nutrition-meal-timestamp-meaning.md)
{% endcontent-ref %}

{% content-ref url="/pages/UP1Wlhf2XqFVHFrf2vTK" %}
[Why is sleep duration shorter than the session window?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/sleep-duration-shorter-than-window.md)
{% endcontent-ref %}

{% content-ref url="/pages/3vIhb2TI8rLP1lDxptiv" %}
[Why doesn't activity end time equal start plus active seconds?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/activity-elapsed-vs-active-seconds.md)
{% endcontent-ref %}

{% content-ref url="/pages/I059NSd7cPBkt6K2DWYb" %}
[What's the difference between resting and average HR in sleep?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/resting-vs-average-hr-scope.md)
{% endcontent-ref %}

{% content-ref url="/pages/gGWyfeP0OHs2nkI4fEMt" %}
[Can I get data in imperial units instead of metric?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/units-metric-only-no-imperial.md)
{% endcontent-ref %}

{% content-ref url="/pages/9etYBg6rRnuBx7HkKY5a" %}
[What units and scales do health and enrichment scores use?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/score-and-enrichment-units-scales.md)
{% endcontent-ref %}

{% content-ref url="/pages/cApMO9nDZq2kQIHn53G1" %}
[What is the difference between body and daily payloads?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/daily-vs-body-payload-differences.md)
{% endcontent-ref %}

{% content-ref url="/pages/CRHdEbuYvt7I5CHdyIFH" %}
[How do I build sleep stage charts from hypnogram samples?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/hypnogram-single-timestamp-reconstruction.md)
{% endcontent-ref %}

{% content-ref url="/pages/sDC4PKz4smkTKEpJOzoV" %}
[Why is a webhook field not in the documented schema?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/schema-source-of-truth-extra-fields.md)
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{% content-ref url="/pages/gh0OSeErCtGdmwmHEM4x" %}
[What's the difference between the three sleep scores?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/three-sleep-scores-explained.md)
{% endcontent-ref %}

{% content-ref url="/pages/cj9Pdp9FomghASo6WWDz" %}
[Does inactivity\_seconds include sleep?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/inactivity-seconds-includes-sleep.md)
{% endcontent-ref %}

{% content-ref url="/pages/w1aIrt4pavnLTKdJAYy5" %}
[What units is the sleep temperature delta in?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/temperature-delta-units.md)
{% endcontent-ref %}

{% content-ref url="/pages/EOMz2ZsizpVM3Xlyuwe3" %}
[Why isn't activity name one of the Terra activity enums?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/activity-name-vs-type-enum.md)
{% endcontent-ref %}

{% content-ref url="/pages/8BUbem6uUgXGp9NOZTBD" %}
[How does the net carbohydrates field work across providers?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/net-carbohydrates-field-and-provider-variance.md)
{% endcontent-ref %}

{% content-ref url="/pages/AH5EdfMZcU7m2ivAIePz" %}
[How do I explore the FHIR output format?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/fhir-format-documentation.md)
{% endcontent-ref %}

{% content-ref url="/pages/ua055mPBLhHDdMmn67gl" %}
[Is the device-to-phone sync timestamp in the payload?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/sync-timestamp-not-exposed.md)
{% endcontent-ref %}

{% content-ref url="/pages/ohsfdl4GwVWTddmjzqK4" %}
[What's in active durations and intensity buckets?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/active-durations-and-intensity-buckets.md)
{% endcontent-ref %}

{% content-ref url="/pages/BjEhDgUm4NjWGBdJrvwY" %}
[Are activity payloads standardised across providers?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/activity-model-standardized.md)
{% endcontent-ref %}

{% content-ref url="/pages/L8uuIDb2gKPbJ1ux1zG5" %}
[Does Terra smooth samples, and why do array lengths differ?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/no-smoothing-sample-array-length-mismatch.md)
{% endcontent-ref %}

{% content-ref url="/pages/hOVk14WKwDyL15G02Y8g" %}
[Are weight and body fat supported in body payloads?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/body-measurements-supported.md)
{% endcontent-ref %}

{% content-ref url="/pages/C3tDp6negVjmGlGbTdw0" %}
[What is RR\_INTERVAL and which devices stream speed?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/rr-interval-and-streaming-coverage.md)
{% endcontent-ref %}

{% content-ref url="/pages/h2njwCaJWmgDjy8N5Mzf" %}
[Why is a WHOOP activity mapped to the wrong type?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/activity-type-mislabel-defaults-to-other.md)
{% endcontent-ref %}

{% content-ref url="/pages/KleCgMXjDu1nIo7N3Cco" %}
[Is visceral\_fat\_level a percentage?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/visceral-fat-level-units.md)
{% endcontent-ref %}

{% content-ref url="/pages/voiEEAuz26jtG8uCFQ7A" %}
[What does the timestamp\_localization metadata field mean?](/faq/help-topics/data-api-sdk/data-model-fields-and-units/metadata-field-meanings.md)
{% endcontent-ref %}