Public Atlas Editorial · Published 2026-09-29 · Updated 2026-09-29. Independent human review pending. Next scheduled review: 2026-10-29. AI-assisted resource.
The short answer
Check when a measurement applies as well as when it was retrieved. A missing value is not zero, and a newly fetched snapshot can still contain an older reading.
Four clocks, four different meanings
| Clock | What it tells you | What it cannot establish |
|---|---|---|
| Observed / prediction window | When the agency measurement applies, or which dates a prediction covers. | Conditions after that observation, or weather effects outside an astronomical tide prediction. |
| Retrieved | When the source bundle was fetched successfully. | That the agency supplied a newer reading. |
| Article updated | When the explanation or underlying content materially changed. | That every embedded measurement was observed on that date. |
| Human reviewed | A recorded editorial review, when a real reviewer and date are provided. | Continuous monitoring. An automated check is not a human review. |
What to do with the number in front of you
- Confirm the identity. Match the place, station identifier, measure, units and reference datum. A nearby station can describe a different location.
- Check the applicable time. For tides, use the station’s local date and covered prediction window. For observations, use the observation timestamp rather than the page-load time.
- Look for missingness. “Unavailable” or a missing day cannot establish a zero value, a stable level or the absence of an event. Do not connect a gap as if it were measured.
- Open the issuing source. Use the page’s source link and compare the same station and measure. If the sources disagree, retain the two dates and values when reporting the issue.
- Choose the appropriate next step. Recheck the official source for a time-sensitive use. If the reading remains unsupported, defer conclusions that depend on it.
Check current source status → · Find the source and station →
Worked examples: how the freshness checks respond
These are hypothetical teaching examples, not reports of actual outages. All four use a fixed check time of 29 September 2026, 12:00 UTC. The result labels below are calculated with the same snapshot helper used by the site. Provider-specific status cards can have different refresh targets; see the status page.
New fetch, old lake reading
Retrieved 29 September at 11:30 UTC; reading dated 25 September.
Result: Reading older than refresh target.
The fetch succeeded, but the reading is older than the lake snapshot helper’s three-day target. The new retrieval does not reset observation age.
Recent reading, old site snapshot
Retrieved 27 September at 23:00 UTC; reading dated 27 September.
Result: Snapshot older than refresh target.
At the example check time, the site snapshot is 37 hours old. Its retrieval age exceeds this helper’s 36-hour target. A date-only source value does not provide an exact observation time.
Prediction window has ended
Recently retrieved bundle; final covered station-local date is 28 September.
Result: Prediction window ended — check NOAA.
It is already 29 September at the reference station. Open NOAA or the current planner for a covered date; an old astronomical prediction is not a present observation.
Timestamp is ahead of the check
Bundle timestamp says 30 September, later than the fixed 29 September check.
Result: Check source timestamp or device clock.
Check the source timestamp and device clock. A timestamp inconsistency must not produce a reassuring freshness badge.
If a value changes without a new date
A changed value for the same observation time may be a source revision; it is not automatically a movement between two times. USGS explains that provisional water data remain subject to revision until reviewed and approved. Our saved-place comparison distinguishes a same-date value change from a newer observation. Read the USGS provisional-data statement ↗
Predictions are a separate product
A tide prediction estimates astronomical high and low water for its station and dates. Observed water levels can differ because of non-tidal influences such as weather. A valid prediction window does not certify water depth, beach access or safe conditions. NOAA’s coastal inundation guide distinguishes predictions, observations and their difference. Read NOAA’s guide (PDF) ↗
Keep a useful correction record
Record the page URL, station ID, measure, displayed value, observation time, retrieval time and the agency source you checked. That gives an editor enough information to reproduce the mismatch. Avoid sending personal location histories.
Corrections process → · Print the source-check checklist → · Read the measurement methods →
Freshness examples describe the Public Atlas snapshot helper as reviewed in code on 29 September 2026. Thresholds are operational checks, not agency guarantees or safety thresholds. This resource does not claim that a human editorial review has occurred.
Common questions
Does a successful refresh guarantee a new measurement?
No. Retrieval records a successful fetch; observation time shows when the measurement applies. Check both.
What does a changed value with the same timestamp mean?
It may be a revision rather than a new observation. USGS provisional values remain subject to correction before final approval.