The North American Datum of 1983, or NAD83, is a crucial system used for mapping and navigation across North America. It was developed to replace the older NAD27 and marked a significant upgrade by integrating modern satellite technology.
This change completely revolutionized fields like construction surveying and geospatial analysis. Before NAD83, professionals relied on traditional methods like triangulation and celestial navigation for mapping and surveying. These techniques were slow–and not very accurate. Now, thanks to NAD83, people can access faster and more precise global positioning and mapping.
What is NAD83?
NAD83 is the third geometric control datum, succeeding NAD27. It was the result of a collaborative project carried out by the National Geodetic Control Survey of the United States, the Geodetic Survey of Canada, and the Danish Geodetic Institute of Greenland.
Although termed NAD of 1983, it was actually released in 1986. It wasn’t until 1990 that state-by-state adjustment was completed for NAD83, and it has been adjusted twice since then, first in 2007 and then in 2011.
Why is NAD83 different from other geometric control datums? Unlike previous geometric control datums, which were based on only terrestrial observations, NAD83 is based on both terrestrial and satellite observations (satellite positioning with Doppler methods and GPS).
This means that it offers significantly improved accuracy and consistency across North America.
What is NAD83 used for?
NAD83 was created to standardize geospatial referencing across North America, but its use has transcended from basic mapping to supporting GPS devices such as smartphones, in-car navigation systems, and drones. Let’s explore how NAD83 does this in more detail.
Location mapping
NAD83 creates a reference frame for the earth so that professionals such as surveyors, geologists, and cartographers can use it to accurately map out different locations using their longitude and latitude as provided by GPS technology.
Navigation technologies
NAD83 integrates with inertial navigation systems (INS), INS applications, and global positioning systems (GPS), providing a foundational reference for these navigation systems.
Why is this necessary? Integrating navigation technologies with NAD83 ensures that all spatial data is accurate by aligning with a standardized and consistent geodetic datum.
Standardized positioning data
Since NAD83 is the standardized datum adopted in North American countries, GNSS applications and NTRIP corrections in the region use NAD83 coordinates. What this means is that all geographic data acquired and processed through these systems are aligned with the NAD83 framework, ensuring consistency and accuracy.
Outside of surveys and mapping, NAD83 is quite useful in other industries and sectors. For example, agricultural farms that use GPS-enabled machinery rely on NAD83 for precision farming practices. Also, the NAD83 geodetic datum ensures that GPS navigation systems provide precise positioning data for air travel.
History of NAD83
Since NAD83 was introduced in 1986, there have been a series of improvements, but before NAD 83, there were other geodetic datums, in order:
NAD27
NAD27 is the predecessor of NAD83 and the second geodetic datum introduced. This geodetic datum is based on the Clarke Ellipsoid of 1866—a reference ellipsoid for NAD27—and originates at the Meades Ranch in Kansas.
This means that the further you move from Kansas, the lower your accuracy will be.
NAD83
NAD83 has been previously described in this article as the standardized geometric datum in North American countries, but it wasn’t just another geodetic datum for mapping and surveying. The framework facilitated the integration of satellite technology into geospatial applications and offered 1m accuracy, which was a spectacular advancement compared to NAD27.
But the NAD83 of 1986 was not without faults and improvement continued, the first of which was HARN.
HARN & HPGN
In geospatial technology, HARN stands for High Accuracy Reference Network. As the first upgrade of NAD83, HARN simply focused on increasing accuracy by attempting a 3D system instead of the existing horizontal, longitude-latitude system.
By introducing fixed height poles, NAD 83 HARN provided a vertical component to the previously two-dimensional data, enabling more precise elevation measurements.
The HPGN (High Precision Geodetic Networks) was introduced for the same purpose as the HARN: to increase accuracy and rework preceding geodetic datums. The HARN and HPGN are so similar in many contexts that it was decided to use “HARN” for both.
So whether you’re referring to high-precision geodetic networks or high-accuracy reference networks, they are both NAD 83 HARN.
CORS networks
The continuously operating reference stations (CORS) are a realization of NAD83 that consists of permanently working GPS receivers. Basically, with the introduction of CORS, we now had GNSS receivers and antennas that could use high-accuracy RTK corrections for high-precision positioning.
Surveyors could also now access GNSS correction services, which was a significant advancement in geodetic technology.
However, modern RTK networks, like Point One’s Polaris, have completely eclipsed CORS in accuracy, reliability, and portability.
CSRS
The Canadian Geodetic Survey (CGS) released a newer version of NAD83, which became the Canadian Spatial Reference System (CSRS). The CSRS defines longitude, latitude, altitude, gravity, and location in Canada.
With the introduction of the CSRS, NAD83 was now NAD83(CSRS), a space-based and 3D dynamic realization as opposed to the original horizontal realization.
CACS
CACS, the Canadian Active Control System, was created in the 1990s to track GNSS satellites used to compute GNSS orbits and clock products to control surveys. This sparse network of control stations provides precise positioning services across Canada, supporting a wide range of applications, including mapping, navigation, and geospatial data collection.
NSRS
The National Spatial Reference System is a consistent coordinate system like the CSRS in Canada. It defines longitude, latitude, altitude, gravity, and location in the United States. The NOAA’s National Geodetic Survey manages it and includes several CORS—continuously operating reference stations.
It also includes permanently marked points (brass, bronze, or aluminum disks), the most recent national shoreline, and accurate models such as geoid, ellipsoid, and atmospheric refraction that affect spatial measurements.
WGS84
With the mainstream use of global positioning systems (GPS), there became a need for a global datum to serve as a reference system, just like the GCS (Geocentric Coordinate System) for satellite navigation systems. This global datum is the world geodetic system of 1984, and it was developed by the US National Geospatial-Intelligence Agency.
WGS84 defines the Earth model from a mathematical perspective and comprises different elements. These include an ellipsoid that approximates the Earth’s shape, a horizontal datum that establishes a standard for latitude and longitude, a vertical datum that defines the reference surface for altitude (height), and a coordinate system for mapping and collecting data.
Other Geographic Coordinate Systems
While the NAD geographic coordinate systems are more popular, there are other geographic coordinate systems, such as the NAVD88 and the ITRF.
NAVD88
The North American Vertical Datum of 1988 (NAVD88) is a vertical control datum that was established in 1991. Unlike horizontal datums such as NAD83 (North American Datum of 1983) and WGS84 (World Geodetic System of 1984), which pinpoint the location on the earth’s surface, this vertical datum gets data on elevation, defining the reference surface for the earth’s altitude.
In 1993, NAVD88 was affirmed as the official datum in the National Spatial Reference System (NSRS).
ITRF
ITRF is the official acronym for the International Terrestrial Reference Frame. Unlike the NAD83, ITRF is not a fixed geographic coordinate system. Its position usually changes and the coordinates refer to epochs—a collection of elevation benchmarks for a given time. So is ITRF better than NAD83?
Experts argue that ITRF and succeeding versions are some of the best and most accurate stable reference frames available. Point One’s real-time kinematic technology provides access to the ITRF2014 epoch coordinate reference system–ensuring high-precision positioning and accurate navigation in real time.
More About NAD 83
Now we’ll answer some of the most popular questions relating to NAD83.
What does NAD 83 mean?
NAD83 is the North American Datum of 1983. It is the geometric datum used in North American countries such as Canada, the United States, Mexico, and Central America for surveying and mapping.
Is NAD83 geographic or projected?
NAD83 (North American Datum of 1983) is neither specifically geographic nor projected; it is a datum used within geographic coordinate systems, and it can also be referenced in projected coordinate systems through various map projections.
Why is NAD 83 more accurate?
NAD83 offers a very high level of accuracy, especially in North America, since it’s based on a network of survey markers that together create a reference frame that considers the flaws of the earth’s form.
What is the spheroid and origin for the North American datum of 1983?
The Origin of the North American Datum of 1983 was the earth’s center of mass, and it uses the Geodetic Reference System of 1980 spheroid.
Access Complete Location Precision with Point One
Surveying and mapping technologies and techniques have improved significantly over the years, from traditional surveying like triangulation to integrating satellite technologies. The history of NAD83 covered in this article shows an upward progression in positioning accuracy from 1-meter precision accuracy with traditional methods to 0.2-meter precision accuracy with GPS.
Today, you can access one-centimeter precision accuracy with real-time kinematic technologies. Point One Navigation is at the forefront of RTK technology, offering reliable and accurate correction services for RTK-enabled devices.
And you don’t have to worry about accessing, choosing, or transforming between datums. Point One makes it effortless to get the right datum for your location–whether that’s local or global. They invented automatic assignment of datums and base stations. You can just connect to a single mount point and they ensure your devices are referencing the closest base stations and the appropriate local datum.
With its Polaris RTK Corrections Network, surveyors can access over 1400 RTK base stations, 99.99% uptime, and less than 5 seconds of network convergence time for centimeter-accurate positioning.
