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NYS ITS GIS Program Office

Geographic Information Systems Clearinghouse

The following recommendations were compiled by the Standards Work Group (now the Standards and Data Coordination Work Group), and have been approved by the Coordinating Body (now the Geospatial Advisory Council).

The intended audience for this standard is the GIS practitioner community of New York throughout all sectors. This is not intended to advise the practice of land surveying.

Datum and Coordinate System Standard

The intent of this standard is to minimize the effort required to use data collected from various sources in New York State. Specifically, the intent is to minimize the number of datum and map projection/coordinate systems combinations in use and to encourage accurate documentation of the systems referenced by data coordinates. Accurate documentation will be especially important during the transition to a new horizontal datum and vertical datum scheduled for 2022. The intent is not to require data providers to convert old data to new coordinate systems, but rather to make clear a preferred set of standards which make sense and provide maximum utility for new technologies.

Datum Recommendations:

NAD-83 - Horizontal

This datum has several adjustments or realizations over the years, so data custodians should document which they are using.

Realization Name                                               Year Adopted

NAD 83 (2011) epoch 2010.00                                   2012
NAD 83 (NSRS2007) epoch 2002.00                       2007
NAD 83 (CORS 96)                                                      1996
NAD 83 (HARN)                                                           1996
NAD 83 (1986)                                                             1986

Note: the GRS-80 ellipsoid should be used with the NAD-83 datum.

NAVD-88 - Vertical

As of the date of this updated standard, the model to transform between ellipsoid coordinates and NAVD88 heights is GEOID 12B.

Coordinate Systems Recommendation:

For data at 1:10,000 scale and larger: State Plane, Meters or U.S. Survey Feet
For data at scales smaller than 1:10,000: UTM Zone 18, Meters

State plane coordinates are most appropriate for large scale applications such as parcel and utility mapping. The state plane coordinate system provides scale distortions of less than one part in 10,000 within any one zone. Smaller scale data sets including 1:24,000 scale quadrangles and digital orthophoto quadrangles should be built on a continuous statewide coordinate system. UTM zone 18 mathematically extended to cover the entire state provides a convenient and appropriate continuous for mid to small scale mapping. The UTM coordinate system provides scale distortions of less than 4 parts in 10,000 inside any zone. UTM zone 18 extended to cover All of New York provides a maximum scale distortion of 15 parts in 10,000 (or a scale factor of 1.0015).

While data may be maintained using the recommendations above, it is now acceptable common practice to publish GIS web services using Web Mercator Auxiliary Sphere (WGS84).