National Geodetic Vertical Datum of 1929
E859786
The National Geodetic Vertical Datum of 1929 is an older United States vertical reference system used to define elevations above sea level before being superseded by NAVD 88.
All labels observed (2)
| Label | Occurrences |
|---|---|
| National Geodetic Vertical Datum of 1929 canonical | 3 |
| NGVD 88 | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T10378052 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: National Geodetic Vertical Datum of 1929 Context triple: [NAVD 88, replaced, National Geodetic Vertical Datum of 1929]
-
A.
Newlands Reclamation Project
The Newlands Reclamation Project is one of the earliest U.S. federal irrigation projects, designed to divert water from the Truckee and Carson Rivers to transform arid Nevada lands into productive agricultural areas.
-
B.
The Basin
The Basin is a popular, sheltered swimming and snorkeling beach on Rottnest Island in Western Australia, known for its clear turquoise water and white sand.
-
C.
The Basin
The Basin is the common nickname for the Basin Reserve, a historic cricket ground and major sporting venue in Wellington, New Zealand.
-
D.
The Basin
The Basin is a naturally formed granite pothole and popular scenic attraction along the Pemigewasset River in Franconia Notch, New Hampshire.
-
E.
Great Stone Dam
The Great Stone Dam is a historic 19th-century granite dam in Lawrence, Massachusetts, built to harness the Merrimack River for industrial waterpower and central to the city’s mill-era development.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: National Geodetic Vertical Datum of 1929 Target entity description: The National Geodetic Vertical Datum of 1929 is an older United States vertical reference system used to define elevations above sea level before being superseded by NAVD 88.
-
A.
Newlands Reclamation Project
The Newlands Reclamation Project is one of the earliest U.S. federal irrigation projects, designed to divert water from the Truckee and Carson Rivers to transform arid Nevada lands into productive agricultural areas.
-
B.
The Basin
The Basin is a popular, sheltered swimming and snorkeling beach on Rottnest Island in Western Australia, known for its clear turquoise water and white sand.
-
C.
The Basin
The Basin is the common nickname for the Basin Reserve, a historic cricket ground and major sporting venue in Wellington, New Zealand.
-
D.
The Basin
The Basin is a naturally formed granite pothole and popular scenic attraction along the Pemigewasset River in Franconia Notch, New Hampshire.
-
E.
Great Stone Dam
The Great Stone Dam is a historic 19th-century granite dam in Lawrence, Massachusetts, built to harness the Merrimack River for industrial waterpower and central to the city’s mill-era development.
- F. None of above. chosen
Statements (49)
| Predicate | Object |
|---|---|
| instanceOf |
United States vertical reference system
ⓘ
geodetic reference system ⓘ vertical datum ⓘ |
| abbreviation | NGVD 29 NERFINISHED ⓘ |
| alsoKnownAs |
NGVD29
NERFINISHED
ⓘ
National Geodetic Vertical Datum of 1929 (NGVD 29) NERFINISHED ⓘ |
| appliesToRegion |
Alaska
NERFINISHED
ⓘ
Canada (limited use) NERFINISHED ⓘ Mexico (limited use) ⓘ conterminous United States NERFINISHED ⓘ |
| basedOn | mean sea level observations at 26 tide gauges in the United States and Canada ⓘ |
| coordinateSystemType | vertical reference system ⓘ |
| country |
United States of America
ⓘ
surface form:
United States
|
| datumType | orthometric height datum ⓘ |
| definedBy | network of geodetic leveling observations ⓘ |
| differenceFrom | NAVD 88 has spatially varying offsets relative to NGVD 29 ⓘ |
| documentationBy |
NOAA National Geodetic Survey
NERFINISHED
ⓘ
National Oceanic and Atmospheric Administration NERFINISHED ⓘ |
| epoch | 1929 ⓘ |
| establishedBy |
National Geodetic Survey
NERFINISHED
ⓘ
U.S. Coast and Geodetic Survey NERFINISHED ⓘ |
| establishedIn | 1929 ⓘ |
| formerName | Sea Level Datum of 1929 NERFINISHED ⓘ |
| hasIssue |
did not account for later improvements in gravity data
ⓘ
inconsistencies in mean sea level between tide gauges ⓘ |
| heightType | orthometric height ⓘ |
| maintainedBy | National Geodetic Survey NERFINISHED ⓘ |
| partOf | National Spatial Reference System NERFINISHED ⓘ |
| reasonForReplacement | need for a more accurate and consistent vertical datum ⓘ |
| referenceSurface | mean sea level as determined in 1929 ⓘ |
| referenceTo | tide gauge observations at multiple tide stations ⓘ |
| relatedTo | North American Datum of 1927 NERFINISHED ⓘ |
| replacedInPracticeBy | NAVD 88 NERFINISHED ⓘ |
| status | superseded ⓘ |
| supersededBy |
NAVD 88
NERFINISHED
ⓘ
North American Vertical Datum of 1988 NERFINISHED ⓘ |
| unitOfMeasure |
foot
ⓘ
meter ⓘ |
| usedBy |
cartographers
ⓘ
civil engineers ⓘ federal agencies in the United States ⓘ state and local governments in the United States ⓘ surveyors ⓘ |
| usedFor | defining elevations above mean sea level ⓘ |
| usedIn |
engineering surveys
ⓘ
floodplain mapping ⓘ hydrologic studies ⓘ topographic mapping ⓘ |
| usedUntil | late 20th century ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: National Geodetic Vertical Datum of 1929 Description of subject: The National Geodetic Vertical Datum of 1929 is an older United States vertical reference system used to define elevations above sea level before being superseded by NAVD 88.
Referenced by (4)
Full triples — surface form annotated when it differs from this entity's canonical label.
this entity surface form:
NGVD 88