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Nebli Marine

The record and methods

What Nebli Marine keeps for every reading, the rules it never breaks, the one limit you should state to others, and where to read how each value is calculated.

Who this is for: the programme lead who answers for the data, and the analyst or reviewer who needs to know exactly what a number is.

Before you start: you are signed in (Getting started). Everything on this page is the same for every role.

What every reading keeps

Every reading in Nebli Marine carries:

  • Two clocks. The drifter's own time and the time the reading arrived. Charts use the drifter's time; status words use the arrival time.
  • Its source. mesh for a reading received over the radio mesh.
  • The firmware version that produced it.
  • Its quality. raw, or suspect with the reason.
  • For a position, its fix quality. A position taken with fewer than four satellites is a weak fix: it is drawn hollow on the map and marked weak fix. A report without a valid fix carries no position at all.

The rules

  • A reading is never edited. What arrived is what is kept and shown.
  • A gap is a gap. No chart, track or export fills in a silence. A track breaks where the drifter was silent.
  • Nothing is dropped. A suspect reading is kept exactly as received, shown dimmed with its reason, and exported with its flag. It is never clamped to a range.
  • A message received twice is recorded once.

Suspect readings

A reading is marked suspect when:

  • Its clock is off. Its device time is more than ten minutes ahead of its arrival, before its campaign started, or more than thirty days before its arrival. A device time behind the arrival time is normal for a reading that waited on the drifter or the gateway, and is never suspect on its own.
  • Its value is out of range. The value lies outside the channel's sensible range.

A message carrying a value that cannot be a measurement of its channel at all, such as a latitude beyond 90°, is refused whole and never enters the record.

While a drifter's latest reading is far from its arrival time, its page says clock off. The hint clears with its next live reading (Drifters in the field).

The audit

Everything a person does to the record is audited, with who did it and when: adopting a drifter and its label, marking it recovered, lost or retired, and exporting. Changes in Settings are recorded with the name of the person who made them.

  • A drifter's page lists its own audit under Audit of this node.
  • Every export includes the audit of what it covers, as its own file (Exports).

One limit to state: mesh readings are not signed

Readings that arrive over the radio mesh are not signed. A radio within range of a gateway could send readings into that campaign, and Nebli Marine cannot tell them apart from a drifter's own.

Every reading received this way carries the source mesh, in the record and in every export. When you present results from mesh readings to a regulator, a funder or the public, state this limit.

Methods: how each value is calculated

The Methods page explains how every value Nebli Marine shows is collected and calculated. Open it from your menu (Methods), or from the how is this calculated? link beside a derived value or rule, such as a drifter's status or mat presence.

The page is grouped into:

  • Channels: position and fix quality, air temperature, air pressure, air humidity, battery.
  • Derived values: sea state, mat presence, drift speed and heading, the estimated position.
  • Record: suspect readings, status words.

Each method has a short card, and Read the full method → opens five parts:

Part What it says
Collection The device, its sensor and how often it samples.
Transmission How the value travels: over the mesh, onto the drifter's card, or not at all.
Formula How the value is calculated, or "none" for a raw value.
Inputs What the calculation uses.
Source The method or standard it follows.

Every method shows the version in force and the date it took effect, with earlier versions folded below. A value made under an earlier version says so beside its link. A raw channel's value has no link, because nothing is calculated from it.

Download methods gives the whole page as one Markdown file, in your language.

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