Units · London and Water

Units used in the charts. Original labels are listed below and kept with the data. Values are unchanged.

Unresolved units

Albury: the EA station definition verifies metres relative to the local stage datum for its mASD measure (gauge datum 56.7 m AOD). A separate measure ending in ---- has source unit ---; we have not relabelled or merged that history. Station definition.

Solar totals and sunshine flags: the Met Office specification describes a 60-minute energy total and sunshine indicators, but labels them with power-per-area units. The ordinary minute irradiance fields retain the stated kW m⁻² unit; contradictory fields stay marked unresolved. No unit conversion is justified by the documentation. Publisher table, page 3.

Unit labels

Source labels	Displayed as	Meaning
m3/s, m³/s, m3s, m³ s⁻¹	$\mathrm{m}^{3}\,\mathrm{s}^{-1}$	Reference
LITRE PER SECOND, L/s	$\mathrm{L}\,\mathrm{s}^{-1}$	Reference
m/s	$\mathrm{m}\,\mathrm{s}^{-1}$	Reference
m, METRE	$\mathrm{m}$	Reference
mAOD	$\mathrm{m}\;\text{(AOD)}$	Metres relative to Ordnance Datum. AOD is a height reference, not a different length unit. Reference
mASD	$\mathrm{m}\;\text{(local stage datum)}$	Metres relative to this gauge’s local stage datum. Do not compare absolute heights at different gauges without a verified datum conversion. Reference
mm, MILLIMETRE	$\mathrm{mm}$	Reference
cm	$\mathrm{cm}$	Reference
km	$\mathrm{km}$	Reference
mm/h	$\mathrm{mm}\,\mathrm{h}^{-1}$	Reference
mg/L, MILLIGRAM PER LITRE	$\mathrm{mg}\,\mathrm{L}^{-1}$	Reference
µg/L, μg/L, ug/L, MICROGRAM PER LITRE	$\mathrm{\mu g}\,\mathrm{L}^{-1}$	Reference
mg/m³, mg/m3	$\mathrm{mg}\,\mathrm{m}^{-3}$	Reference
µg/m³, μg/m³, ug/m3	$\mathrm{\mu g}\,\mathrm{m}^{-3}$	Reference
MILLIGRAM PER KILOGRAM, mg/kg	$\mathrm{mg}\,\mathrm{kg}^{-1}$	Reference
MICROGRAM PER KILOGRAM, µg/kg	$\mathrm{\mu g}\,\mathrm{kg}^{-1}$	Reference
µS/cm, μS/cm, MICROSIEMENS PER CENTIMETRE	$\mathrm{\mu S}\,\mathrm{cm}^{-1}$	Reference
mS/cm	$\mathrm{mS}\,\mathrm{cm}^{-1}$	Reference
CELSIUS, CELCIUS, Celsius, Celcius, celsius, celcius, C, °C, oC, ºC, degC, deg C, degrees Celsius	${}^{\circ}\mathrm{C}$	Reference
K	$\mathrm{K}$	Reference
%, PERCENTAGE	$\%$	Reference
hPa	$\mathrm{hPa}$	Reference
V	$\mathrm{V}$	Reference
MW	$\mathrm{MW}$	Reference
GRAM, g	$\mathrm{g}$	Reference
MILLILITRE, mL	$\mathrm{mL}$	Reference
ft	$\mathrm{ft}$	Feet; original values retained. Reference
knots	$\mathrm{kn}$	Knots; original values retained. Reference
degrees true	${}^{\circ}\;\text{(true)}$	Bearing relative to true north. Reference
kW/m², kW/m² (publisher specification)	$\mathrm{kW}\,\mathrm{m}^{-2}$	Publisher’s stated irradiance unit; any metric-specific uncertainty remains in the source notes. Reference
publisher lists kW/m²; unresolved	$\mathrm{kW}\,\mathrm{m}^{-2}\;\text{(unresolved)}$	The publisher specification is unresolved for this metric. No conversion or correction has been applied.
colonies/100 mL	$\text{colonies}\,(100\,\mathrm{mL})^{-1}$	Colonies per 100 millilitres. The factor 100 is retained; no rescaling. Reference
Colony Forming Units / 100ml	$\mathrm{CFU}\,(100\,\mathrm{mL})^{-1}$	Colony-forming units per 100 millilitres. Not merged with generic counts or another analytical method. Reference
NUMBER PER HUNDRED MILLILITRES	$\text{count}\,(100\,\mathrm{mL})^{-1}$	Count per 100 millilitres. The unit alone does not specify the counting method. Reference
Number per year	count per year	Original annual counting basis retained; no conversion to a fixed number of seconds. Reference
Hours (Decimal)	$\mathrm{h}$	Decimal hours. Reference
HOUR (HH.MM)	HH.MM	Publisher’s hours-and-minutes notation; this is not decimal hours.
NTU, NEPHELOMETRIC TURBIDITY UNITS	$\mathrm{NTU}$	Nephelometric turbidity units. Keep the measurement method; do not convert to FTU or FNU. Reference
FORMAZIN TURBIDITY UNIT, FTU	$\mathrm{FTU}$	Formazin turbidity unit. Its instrument definition cannot be inferred from the name alone. Not equated to NTU. Reference
RFU	$\mathrm{RFU}$	Relative fluorescence units; not a mass concentration. Instrument and calibration matter. Reference
PSU	PSU (practical salinity)	Publisher’s PSU notation retained. Practical salinity is dimensionless on PSS-78; it is not grams per kilogram. Reference
Parts per thousand	‰	Parts per thousand. Not equated to practical salinity (PSU). Reference
PH UNITS	pH (dimensionless)	pH is a logarithmic quantity, not a physical unit. Reference
dimensionless, UNITLESS VALUE	dimensionless	The publisher states that this quantity is dimensionless. Reference
NUMBER	count	Reference
COLOUR, HAZEN, Hazen	$\text{Hazen}$	EA unit code 904 explicitly gives COLOUR the alternative label HAZEN. A colour scale, not a measured platinum concentration. Reference
---	unit not supplied	The publisher supplied “---”, not a usable unit. No unit or datum is inferred from another gauge. Reference
binary; publisher unit conflict	binary flag (unit conflict)	The field description defines a sunshine indicator but the unit column says irradiance. Values are retained as codes, not physical irradiance. Reference
oktas	oktas	Cloud-cover scale retained; not converted to percent.
Coded Result	coded result	Publisher’s code or scale; not a physical unit.
GARBER Survey Assessment Scale Code	GARBER assessment code	Publisher’s code or scale; not a physical unit.
NATIONAL GRID REFERENCE (METRIC)	metric grid reference	Publisher’s code or scale; not a physical unit.
PRESENT/NOT FOUND	present / not found	Publisher’s code or scale; not a physical unit.
Text Result	text result	Publisher’s code or scale; not a physical unit.
YES(1) OR NO(0)	yes (1) / no (0)	Publisher’s code or scale; not a physical unit.
METAR-style code	METAR-style code	Publisher’s code or scale; not a physical unit.
low / nominal / high	low / nominal / high	Publisher’s code or scale; not a physical unit.
community intensity scale	community intensity scale	Publisher’s code or scale; not a physical unit.
magnitude scale	magnitude scale	Publisher’s code or scale; not a physical unit.
Modified Mercalli scale	Modified Mercalli scale	Publisher’s code or scale; not a physical unit.