NDFD Spatial Reference System - MDL
NDFD Grids
NDFD data are stored as points on regular grids. There are 6 grids with each grid derived from points projected from a sphere of radius 6371.2 km. The CONUS and Northern Hemisphere grids use a Lambert Conformal projection while the Guam, Hawaii, Puerto Rico, and Northern Pacific grids use a Mercator projection. The Alaska grid is based on a Polar Stereographic projection. Additional meta-data on NDFD grids are available in three grid definition tables below.
NDFD Horizontal Datum
The NDFD uses the WGS84 geoid.
Grid Locations and Extent
CONUS Grid
Northern Hemisphere Grid
Alaska Grid
Guam Grid
Hawaii Grid
Puerto Rico Grid
Northern Pacific Grid
Oceanic Grid
Micronesia Grid
Details of NDFD Grids Found in GRIB2 Meta Data
The NDFD grids, as described in the tables below, are the result of projecting a sphere onto a flat surface. The corner of the grid is found at the point identified in the grid parameters tables as latitude1 and longitude1. Each table lists the number of points in the grid which is the product of the number of points on the parallel and meridian. Grid points are seperated by Dx meters along the x axis (longitude) and Dy meters along the y axis (latitude). The projection type, earth radius, and other grid definition parameters are provided in the tables below. For more information on decoding GRIB2 files, see https://vlab.noaa.gov/web/mdl/ndfd-grib-encoding.
CONUS and Northern Hemisphere Grids
| Grid Parameter | CONUS 5km | CONUS 2.5km | Northern Hemisphere |
|---|---|---|---|
| Number of Points | 739297 | 2953665 | 1509825 |
| Projection Type | Lambert Conformal | Lambert Conformal | Lambert Conformal |
| Shape of Earth | sphere | sphere | sphere |
| Earth Radius | 6371.2 km | 6371.2 km | 6371.2 km |
| Number of Points on the parallel | 1073 | 2145 | 1473 |
| Number of Points on the Meridian | 689 | 1377 | 1025 |
| Latitude1 | 20.191999 | 20.191999 | 12.189999 |
| Longitude1 | 238.445999 | 238.445999 | 226.541000 |
| u/v vectors relative to | easterly/northerly | easterly/northerly | easterly/northerly |
| Dx | 5079.406 m | 2539.703 m | 5079.406 m |
| Dy | 5079.406 m | 2539.703 m | 5079.406 m |
| GRIB2 grid, scan mode | 64 (0100) | 64 (0100) | 64 (0100) |
| Scan i/x direction | positive | positive | positive |
| Scan j/y direction | positive | positive | positive |
| Consecutive points in | i/x direction | i/x direction | i/x direction |
| Adjacent rows scan in | same direction | same direction | same direction |
| Mesh Latitude | 25 | 25 | 25 |
| Orientation Longitude | 265 | 265 | 265 |
| Which Pole is on the Plane | north | north | north |
| Is Projection Bi-polar | no | no | no |
| Tangent Latitude1 | 25 | 25 | 25 |
| Tangent Latitude2 | 25 | 25 | 25 |
| Southern Latitude | -90 | -90 | -90 |
| Southern Longitude | 0 | 0 | 0 |
Guam, Hawaii, Puerto Rico Grids, Northern Pacific and Oceanic Grids
| Grid Parameter | Guam | Hawaii | Puerto Rico | N. Pacific | Oceanic |
|---|---|---|---|---|---|
| Number of Points | 37249 | 72225 | 75936 | 1580529 | 4512981 |
| Projection Type | Mercator | Mercator | Mercator | Mercator | Mercator |
| Shape of Earth | sphere | sphere | sphere | sphere | sphere |
| Earth Radius | 6371.2 km | 6371.2 km | 6371.2 km | 6371.2 km | 6371.2 km |
| Number of Points on the parallel | 193 | 321 | 339 | 1473 | 2517 |
| Number of Points on the Meridian | 193 | 225 | 224 | 1073 | 1793 |
| Latitude1 | 12.349884 | 18.072699 | 16.977485 | -25.000000 | -30.4192 |
| Longitude1 | 143.686538 | 198.474999 | 291.972167 | 110.000000 | 129.906000 |
| u/v vectors relative to | easterly/northerly | easterly/northerly | easterly/northerly | easterly/northerly | easterly/northerly |
| Latitude2 | 16.794399 | 23.087799 | 19.544499 | 60.643999 | 79.991525 |
| Longitude2 | 148.280000 | 206.130999 | 296.015600 | 250.871000 | 10.689223 |
| Dx | 2500.0 m | 2500.0 m | 1250.0 m | 10000.0 m | 10000.0 m |
| Dy | 2500.0 m | 2500.0 m | 1250.0 m | 10000.0 m | 10000.0 m |
| GRIB2 grid, scan mode | 64 (0100) | 64 (0100) | 64 (0100) | 64 (0100) | 64 (0100) |
| Scan i/x direction | positive | positive | positive | positive | positive |
| Scan j/y direction | positive | positive | positive | positive | positive |
| Consecutive points in | i/x direction | i/x direction | i/x direction | i/x direction | i/x direction |
| Adjacent rows scan in | same direction | same direction | same direction | same direction | same direction |
| Mesh Latitude | 20 | 20 | 20 | 20 | 20 |
| Orientation Longitude | 0 | 0 | 0 | 0 | 0 |
| Tangent Latitude1 | 0 | 0 | 0 | 0 | 0 |
| Tangent Latitude2 | 0 | 0 | 0 | 0 | 0 |
| Southern Latitude | 0 | 0 | 0 | 0 | 0 |
| Southern Longitude | 0 | 0 | 0 | 0 | 0 |
Alaska Grid
| Grid Parameter | Alaska 6km | Alaska 3km |
|---|---|---|
| Number of Points | 456225 | 1822145 |
| Projection Type | Polar Stereographic | Polar Stereographic |
| Shape of Earth | sphere | sphere |
| Earth Radius | 6371.2 km | 6371.2 km |
| Number of Points on the parallel | 825 | 1649 |
| Number of Points on the Meridian | 553 | 1105 |
| Latitude1 | 40.530101 | 40.530101 |
| Longitude1 | 181.429000 | 181.429000 |
| u/v vectors relative to | easterly/northerly | easterly/northerly |
| Dx | 5953.125 m | 2976.5625 m |
| Dy | 5953.125 m | 2976.5625 m |
| GRIB2 grid, scan mode | 64 (0100) | 64 (0100) |
| Scan i/x direction | positive | positive |
| Scan j/y direction | positive | positive |
| Consecutive points in | i/x direction | i/x direction |
| Adjacent rows scan in | same direction | same direction |
| Mesh Latitude | 60 | 60 |
| Orientation Longitude | 210 | 210 |
| Which Pole is on the Plane | north | north |
| Is Projection Bi-polar | no | no |
| Tangent Latitude1 | 90 | 90 |
| Tangent Latitude2 | 90 | 90 |
| Southern Latitude | 0 | 0 |
| Southern Longitude | 0 | 0 |
Micronesia Grid
| Grid Parameter | Micronesia | ||||
|---|---|---|---|---|---|
| Number of Points | 444507 | ||||
| Projection Type | Mercator | ||||
| Shape of Earth | sphere | ||||
| Earth Radius | 6371.2 km | ||||
| Number of Points on the parallel | 1041 | ||||
| Number of Points on the Meridian | 427 | ||||
| Latitude1 | 0.0258958 | ||||
| Longitude1 | 129.81 | ||||
| u/v vectors relative to | easterly/northerly | ||||
| Latitude2 | 20.0036 | ||||
| Longitude2 | 179.579 | ||||
| Dx | 5000.0 m | ||||
| Dy | 5000.0 m | ||||
| GRIB2 grid, scan mode | 64 (0100) | ||||
| Scan i/x direction | positive | ||||
| Scan j/y direction | positive | ||||
| Consecutive points in | i/x direction | ||||
| Adjacent rows scan in | same direction | ||||
| Mesh Latitude | 20 | ||||
| Orientation Longitude | 0 | ||||
| Tangent Latitude1 | 0 | ||||
| Tangent Latitude2 | 0 | ||||
| Southern Latitude | 0 | ||||
| Southern Longitude | 0 |
GRIB2 Links
GRIB2 Documentation
- World Meteorological Organization FM92 GRIB, Edition 2, Code Form and Tables publication
- GRIB2 Use at NCEP