**Bead** `c6a0e375-a699-45cc-8c8c-f2bf4558e930` · [canonical URI](https://redfish.acequia.io/guerin/.agents/c6a0e375-a699-45cc-8c8c-f2bf4558e930/) · discussion: Talk: Crs Strategy This page is the wiki facet of a [bead](https://redfish.acequia.io/guerin/.agents/); the bead is the source of truth.
## Identity - **URI:** https://redfish.acequia.io/guerin/.agents/c6a0e375-a699-45cc-8c8c-f2bf4558e930/ - **GUID:** `c6a0e375-a699-45cc-8c8c-f2bf4558e930` - **Name:** crs-strategy - **Opened:** 2026-07-02 (parciante: guerin)
## Motivation (why a GUID) A place to weigh the benefits of different coordinate reference systems (CRS) against the use case they serve: which CRS to store in, display in, measure in, analyze in, render a globe in, and interchange in. It grows out of concrete tooling in the sibling bead [`3d011d4e` user-host-layer](https://redfish.acequia.io/guerin/.agents/3d011d4e-3212-477c-aa3f-a058e24aa36a/about.md): a Leaflet viewer that reprojects a source raster per tile, and a browser COG converter that now offers reproject-to-4326 / 3857 / keep-original. Those forced the question this bead answers in general.
## Mechanism (what this bead does) Holds a decision framework: a CRS-family x use-case matrix, the properties that drive the choice (distortion class, units, zoned-vs-global, datum/epoch/vertical, tiling-ecosystem support), and the acequia-specific stance (a CRS is a soft, per-interaction facet of a place-URI, not a reified single truth; prefer reproject-on-read over reproject-on-store). Exploratory and additive.
## Folder layout ``` c6a0e375-.../ ├── about.md ├── uploads/ └── 2026-07-02/ ├── notes/ │ ├── 00-crs-strategy-matrix.md # CRS families x use cases, the decision framework │ └── 01-reproject-on-read-vs-store.md # where the reprojection happens, and why ├── chats/ │ └── 2026-07-02-crs-strategy.md └── artifacts/ ```
## Session log - **2026-07-02** — Bead opened via `start-bead crs-strategy`, alongside adding a 4326/3857/keep Output-CRS control to the COG converter in bead `3d011d4e`. Wrote the CRS matrix and the reproject-on-read-vs-store note.
## Modus operandi (how to interact) Read [notes/00-crs-strategy-matrix.md](https://redfish.acequia.io/guerin/.agents/c6a0e375-a699-45cc-8c8c-f2bf4558e930/2026-07-02/notes/00-crs-strategy-matrix.md) first. Deposit CRS use cases, corrections, or new axes into [uploads/](https://redfish.acequia.io/guerin/.agents/c6a0e375-a699-45cc-8c8c-f2bf4558e930/uploads/).
## Capabilities A reference the dev ecology can cite when a tool has to pick or offer a CRS (converters, tilers, catalog writers, pose/calibration solvers).
## Lifecycle Open, exploratory, apoptotic. Static markdown; no dangling state.
## Limitations Opinionated defaults, not doctrine. EPSG codes and proj strings should be verified against epsg.io / PROJ at use time; datum realizations and epochs drift.
## References (bead cross-links) - Bead: User Host Layer · [canonical](https://redfish.acequia.io/guerin/.agents/3d011d4e-3212-477c-aa3f-a058e24aa36a/)
See all: Beads