# Interpreting strata

> Group the logged geology into your project's own strata, see them on sections, and summarise results by them.

A log records what was found in each hole. An **interpretation** says how those
layers line up across the site: which logged layers belong to the same unit.
In GIMLabs you set up the project's **strata** and assign each logged geology
layer to one of them.

The logs are never changed. The interpretation sits alongside them, and you can
change it whenever your view of the ground changes.

<Steps>

<Step title="Set up the project's strata">

Open **Sections** in the map's side panel. Under **Project strata**, either
**Add a stratum** or **Start from the logs' geology codes**, which drafts one
stratum for each geology code already logged on the project.

Click a stratum to give it a name, a code, the pattern it is drawn with (from
your geology legend), a colour, a soil class and a formation. The strata belong
to the project, so every section on it shares them.

</Step>

<Step title="Open a section on screen">

Open a section, or a schematic of the holes you want to compare, from its
**Generate** menu with **Open in split** or **Open full**. The section's panel
reminds you of this step if it is not open yet.

</Step>

<Step title="Pick bands and assign them">

Click a band on the drawing to pick it. **Shift-click** or drag a box to pick
several, across holes too. The picked bands are listed in the panel with their
depths and descriptions.

Choose a stratum under **Assign to**, or **Unassign** to take the bands out of
one. A stratum you have not set up yet can be added from the same list.

</Step>

</Steps>

You can also assign from the [table editor](/manage/table-editor): the geology
table has an **Interpreted Stratum** column, and **bulk update** offers it as a
field, which is quicker for many rows at once.

## Showing strata on a section

The **Interpreted** setting on each section decides whether its drawing shows
the interpretation:

- **Off**, the default, draws the geology as logged.
- **Beside the geology** adds an interpreted column next to each hole's logged
  geology, so the two can be read side by side.
- **Instead of the geology** draws the geology column as interpreted strata.

The legend names each stratum on the drawing, with its pattern and colour.
Layers not assigned to a stratum are left blank, so the column still accounts
for every logged metre.

Your section logs do not need changing for this: the interpreted column is
added to whichever section log the section uses.

<Callout type="note" title="A blank interpreted column">
  If the interpreted column is empty, the project has no strata yet, or none of
  the holes on the drawing has been assigned. The section's panel warns you
  when the setting is on and there are no strata.
</Callout>

## Where assignments are kept

By default GIMLabs keeps which stratum each geology row is in. Under **Where
assignments are kept** you can instead keep them in one of your own geology
fields, so the interpretation travels with your data as a value in that field.
If assigning would replace something already in the field, you are asked first,
and each row's history records the change.

**Take assignments from a field** is for an interpretation that came in with the
data: it reads the strata from one of your geology fields, and leaves the field
as it is.

## In exports and imports

AGS and CSV exports carry the interpretation in a column of its own on the
geology table:

| Format | Column |
| --- | --- |
| AGS | `GEOL_INTP`, declared in the DICT group |
| CSV | `Interpreted stratum` |

Importing a file with that column assigns the rows by stratum name, adding any
stratum the project does not have yet. **Fill gaps only** assigns only rows that
have no stratum yet; **Overwrite all** also takes a row out of its stratum when
the file leaves it blank. The import's details show how many rows were assigned
and which strata were added.

The same codes are listed under the geology table's fields in Product OS. They
are reserved, so no field of your own can use them.

## Summarising results by stratum

In a figure set, the **Summary of Results by Stratum** can be **Named by:
Interpreted stratum**, so each test result is counted under the stratum its
geology row is in. Results in rows with no stratum are listed as
**Unassigned**.

### Discounting a reading

If one result is clearly wrong - a mistyped value, a disturbed sample - you
can leave it out of its stratum's statistics without deleting it. In the figure
set, open **Review readings**, choose the stratum and parameter, and
**Discount** the reading, with an optional reason. It is left out on every
summary on the project, so they all agree. The summary's notes name each
discounted reading and the reason, so the figure says what was left out.
**Put back** restores it.