Projecting a planar bed into a geological section
For a locally planar bed with true dip δ, choose horizontal x toward its down-dip direction and elevation z upward.
Key knowledge
For a locally planar bed with true dip δ, choose horizontal x toward its down-dip direction and elevation z upward. Its plane satisfies z=z₀−x tanδ. A vertical section making horizontal angle β to strike has apparent dip magnitude α with tanα=tanδ|sinβ|. A section normal to strike displays the true dip; a section along strike displays no dip for a nonvertical bed.
Values and equations
z=z₀−x tanδ; tanα=tanδ|sinβ|
- z,z₀,x
- elevation, reference elevation and horizontal down-dip displacement m
- δ,α,β
- true dip, apparent dip magnitude and section angle to strike rad
Conditions and scope
- 0≤δ<π/2; use one unwarped plane and the actual horizontal direction of the section. A horizontal bed has no unique strike.
- Vertical beds require a separate intersection calculation: the tangent formula is singular. Curved folds, faults, topography and vertical exaggeration need explicit geometry; sparse surface attitudes do not uniquely determine the subsurface.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the actual attitude definitions, horizontal/vertical exceptions and section/map descriptions. The plane and apparent-dip formulas are an explicit trigonometric projection derived from those definitions, not a formula claimed printed on the page; excluded the blanket inference that all sedimentary beds were originally horizontal.
2026-10-10 · Independent AI editorial review: All73 exact supplement compact statements, conditions, displayed equations and247 origin semantic links read; all109 combined original36+supplement73 author-source rows, exact locators, hypotheses, exclusions and disclosed derivations assessed. Original36 exact scientific content is independently approved in the linked receipt. All18 inherited Earth compact references and shared Math/Physics/Measurement methods were considered in the full practical Earth inventory. Targeted actual primary sections listed below; not every source body/proof or every possible university elective independently reread. AI editorial reference review, not human certification, full-degree proficiency, new experimental validation or a claim of whole combined Earth-and-Cosmos approval. Receipt: earth-completion-independent-content-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-apparent-dip-section
- Revision
- core.1
- Structured reference record
- University core expansion