# DepthScout regional survey-coverage snapshot

This dataset supports the DepthScout Research report **“The Uneven Map Beneath the Water.”** It freezes the public catalog as observed on August 13, 2026.

## Files

- `depthscout-regional-survey-coverage-2026-08-13.csv`: one row for each of the 63 public regional catalogs.

## Fields

| Field | Definition |
|---|---|
| `snapshot_date` | Date the public pages were collected. |
| `region` | Display name used on DepthScout. |
| `slug` | Regional route slug. |
| `catalog_placements` | Waters listed in that regional catalog. This is not a deduplicated national count. |
| `survey_backed_placements` | Regional placements labeled “Survey depth data.” |
| `approximated_placements` | `catalog_placements - survey_backed_placements`. |
| `survey_backed_percent` | `survey_backed_placements / catalog_placements × 100`, rounded to two decimal places. |
| `source_url` | Public DepthScout regional page used for the row. |

## National versus regional totals

The DepthScout homepage reported a sitewide catalog total of **37,672 waters**, of which **14,343** were labeled “Survey depth data” (38.1%).

Summing the 63 regional rows produces **37,905 catalog placements**, of which **14,482** were survey-backed (38.2%). These are placements, not a deduplicated national count. A shared or border water can appear in more than one regional catalog, so the regional sum must not be substituted for the sitewide total.

## Interpretation limits

- The dataset measures survey-backed coverage inside DepthScout’s catalog. It is not a census of every bathymetric survey held by every public agency.
- A zero does not prove that no survey exists. It means no placement in that DepthScout regional catalog carried the survey-data label on the snapshot date.
- “Survey-backed” identifies the origin of the contours. It does not grade survey age, sounding density, horizontal accuracy, vertical datum, or fitness for navigation.
- DepthScout changes over time. Reproduce the analysis against this frozen file rather than combining it with later live counts.

## Core calculations

- Sitewide catalog coverage: `14,343 / 37,672 = 38.1%`
- Regional placement coverage: `14,482 / 37,905 = 38.2%`
- Regions at or above 90%: `18`
- Regions below 10%: `16`
- Placements in below-10% regions: `15,474`, with `93` survey-backed (`0.6%`)
- Survey-backed placements in the five largest contributing regions: `9,647 / 14,482 = 66.6%`

## Suggested public path

`/research/data/depthscout-regional-survey-coverage-2026-08-13.csv`