# Layer and Stratigraphy ## Layer & Stratigraphy Model The Layer Data section stores soil/rock layers with their descriptions. Layers in G1 must be entered by hand — layer by layer via "Add Ground Description". Each layer requires selection of a Ground Description Standard (e.g. BS5930 Walker, ASTM) from a dictionary of available standards. Once a standard is chosen, the user can "Explode" the selection to move into Borehole Log + Layers entry mode. New layers are added via right-side buttons; each new layer adds one level below, and layer depth is entered as Depth 2 (final depth), which becomes Depth 1 of the next layer. Sublayers can be created inside a parent layer with their own from/to boundaries, rendered as a small break in the main fill pattern with an additional from/to line in the description. Inside a layer, ground type is selected from categories: fine-grain cohesive soil, cohesionless coarse-grain, peat, soft rock, rock. After ground type selection, the Data Collection Standard dropdown controls field patterns (e.g. "Geotechnical English" vs other local configurations). Primary soil type, secondary soil type, and minor constituents are each chosen from their own dictionaries, followed by plasticity, strength, and consistency. Transition notation: a minus sign denotes a transition between two components (e.g. `silty - gravelly`), rendered with an additional vertical band in the fill pattern. Compound terms such as "medium silty" or "fine and gravelly sand" can be created by chaining dictionary terms. Layer descriptions are auto-generated as a text field from the selected properties; users can override with free-text edits. The "Generate Layer Description" button regenerates the sentence from the underlying parameters, overriding any user edits. Layer Data parameters include "dev to" (depth to / bottom depth), ground unit, and geological description. Changing the ground description standard on an existing layered borehole will delete the layers (meaning is not preserved across standards); the workaround is to add a second ground description in the new standard and copy layers across via Copy Borehole Log Properties. When saving, GeoDin warns about layer properties valid in one standard but not the target standard (e.g. BS phrasing that does not translate to ASTM), flagging the specific soil property. GeoDin ships a PDF guide explaining ground description standards, codewords, transition conventions, and how to build custom ground descriptions. Borehole log properties (layer data) can be copied from one borehole to another, even across databases, via `Copy Borehole Log` — layers transfer, but some standard-specific codes may not translate automatically. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.geodin.com/concepts/layer-and-stratigraphy.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.