Proposal:Surface=laterite - OpenStreetMap Wiki

Proposal:Surface=laterite

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surface=laterite

Proposal status:

Proposed (under way)

Proposed by:

Julcnx

Tagging:

surface=laterite Data item

Applies to:

way

Definition:

A road, track, or path surfaced with lateritic soil: a cohesive, usually red/orange, iron-oxide-rich tropical/subtropical soil that hardens when dry but rapidly becomes slippery and potentially impassable on first wetting, then deeply plastic and adhesive under sustained rain. This proposal also includes a conditional documentation update to Tag:surface=clay to distinguish laterite from clay-mineral soils.

Draft started:

2026-04-21

RFC start:

2026-05-19

Want to see the result without reading the full proposal? Jump to how the page would look like after approval.

Note for readers: this proposal addresses a surface type found almost exclusively in tropical and subtropical regions. Readers are encouraged to read the community input from mappers with direct on-the-ground experience in these areas before forming a view.

SUMMARY<br>What: surface=laterite documents the red/orange tropical road soil that mappers currently fall back to surface=dirt, surface=ground, or sometimes surface=clay for lack of a dedicated value: the broader family of iron-oxide-influenced lateritic soils, covering roughly one third of continental land area across Africa, Southeast Asia, and Latin America.

Why it matters: Laterite has two predictable seasonal states: firm and dusty when dry; slippery and potentially impassable when wet. The wet transition is abrupt: on first rain the surface becomes near-frictionless and slippery within minutes before softening to full depth plasticity. Generic tags like surface=dirt do not capture this behaviour.

Bot context: A recurrent bot moved surface=laterite to material=laterite without adding a fallback surface=* tag; an OSH history audit confirmed 711 such transitions in Cambodia and Cameroon, leaving the surface key absent on each. The bot is now stopped. This proposal reinstates and documents the signal those migrations removed.

Laterite is not clay: laterite is red/orange and hardens in dry season; genuine clay-dominant soils like black cotton (Vertisol) stay dark grey or black and do not harden. Both are sticky when wet, which is why the confusion happens. Iron oxides dominate in laterite, not clay minerals. Clay minerals are naturally white to light-coloured; the intense red/orange comes from iron-oxide influence, not clay impurities. After this proposal surface=clay on roads is a rare edge case; sports courts are unaffected.

Why "laterite" not "lateritic" or "murram": OSM surface values use material nouns, not adjectives, ruling out surface=lateritic. surface=murram is accurate but East African only. "Laterite" is the most globally intelligible term across regional names (murram, terra roxa, din daeng, rahnrahn); the scope section defines exactly which soils it covers.

Community support: 39 mappers confirmed the field description or provided relevant regional context; 2 engaged critically with geological scope and verifiability. Respondents cover Madagascar (three independent confirmations), Cameroon, Senegal, Thailand, Cambodia, Colombia, Brazil, DR Congo, Kenya, South Africa, Philippines, Bolivia, Argentina, India, Ghana, and West/Central Africa, including a soil engineer with direct Cameroon field experience.

If rejected: surface=clay is already documented and will continue to absorb laterite usage. Rejection does not produce cleaner tagging; it preserves and entrenches the existing clay/laterite conflation.

Contents

1 Supporting pages

2 Problem

3 Proposal

3.1 Scope

3.2 Verifiability

4 Rationale

4.1 What laterite is

4.2 Why surface=laterite

5 Likely objections and responses

6 Features/Pages affected

6.1 Post-approval consumer outreach

7 How the wiki would look if passed

7.1 Field identification

7.2 Tagging

7.2.1 Recommended combinations

7.2.2 Relations to other tags

7.3 Possible tagging mistakes

7.4 Examples

7.5 Counter-examples

7.6 See also

8 External discussions

9 Community input

10 Comments

11 Changes during RfC

12 References

Supporting pages

Detailed background is in the supporting subpages:

Soil science, regional names, road engineering, and field identification

Usage data, snapshot analysis, and bot migration history

Community input and outreach responses

Problem

Laterite is a major unpaved-road material across tropical Africa, Southeast Asia, and Latin America,[1] yet OSM has no documented surface=laterite value.

Mappers fall back to surface=dirt, surface=ground, or surface=clay, none of which capture laterite's key characteristic: it is firm and trafficable in dry season but becomes slippery and potentially impassable within minutes of first rain, then deeply plastic under sustained wet.

A recurrent bot migration converted surface=laterite to...