Geolocation Tools

NSIDC provides software tools to extract and geolocate data in a polar stereographic projection derived from gridded passive microwave data sets at NSIDC, as well as masking tools that limit the influence of weather effects on sea ice concentrations. We also provide software and tools for geolocating and displaying EASE-Grid data sets at NSIDC. For a complete list of these data sets, see the Data Sets Web Page.

This page provides links to software and tools for geolocating and displaying EASE-Grid and polar stereographic projection data sets available at NSIDC. All tools are available by FTP.

Table of Contents

  1. EASE-Grid Data Tools
    1. NSIDC DataViewer
    2. Geolocation Software
    3. Geolocation Data Files
    4. Additional Tools for EASE-Grid
  2. Polar Stereographic Data Tools
    1. Data Extraction Tools
    2. Data Display Tools
    3. Geocoordinate and Pixel-Area Tools
    4. Masks and Overlays

EASE-Grid Data Tools

The software and tools are grouped into the following categories:

  • NSIDC DataViewer - Interactive tool for viewing and displaying satellite images for a variety of passive microwave data
  • Geolocation Software - Including C, FORTRAN, and IDL (Interactive Data Language) conversion software
  • Geolocation Data Files - Look-up files that contain arrays with the latitude and longitude at the center of each grid cell
The look-up files for EASE-Grid data sets contain arrays with the latitude and longitude at the center of each grid cell. Users who need software to perform the conversion for any location, not just the center of each cell, can choose from the tools listed below or can obtain the Map Transformations Library (Mapx) software.

NSIDC DataViewer

Tool Name dataviewer.tar.gz
Applicable Data Sets
Polar Stereographic Projection
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
 
EASE-Grid Projection
Near-Real-Time SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent Version 4
 
Quarter-Degree Projection
AMSR-E/Aqua Daily Global Quarter-Degree Gridded Brightness Temperatures
Description The NSIDC DataViewer is an interactive tool for viewing and displaying satellite images from select NSIDC passive microwave data sets. Images in PNG, JPEG, TIFF, and other commonly used image data formats can also be viewed and displayed in a user-defined grid.

Up to 64 images can be displayed simultaneously in the DataViewer resizeable graphics window, allowing data users to page through a series of images. Images can be scaled and manipulated either individually or as a group. By moving the cursor over an image, a data user can obtain the latitude and longitude coordinates as well as the image value at the cursor location. After an image or series of images is manipulated, the contents of the graphics window(s) can be saved in a variety of image formats, including PostScript, PNG, JPEG, and TIFF.

The DataViewer is a program written in Interactive Data Language (IDL). It can be run in IDL with an IDL license, via the freely distributed IDL Virtual Machine, or as a run-time application.

Please Note:
  • DataViewer produces a scaling error with time values in DMSP-F17 SSMIS time (.tim) files. When using SSMIS .tim files, please be advised that data points will display as 1/10th of their actual value.
Access FTP

Geolocation Software

Tool Name easeconv.pro (Located in easeconv-0.3.tgz)

(With the help file, easconv_help.html, for data set users with IDL)
Tool Type IDL
Applicable Data Sets AARI 10-Day Arctic Ocean EASE-Grid Sea Ice Observations
AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua 5-Day L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Monthly L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Daily L3 Surface Soil Moisture, Interpretive Parms, & QC EASE-Grids
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Global Monthly EASE-Grid Snow Water Equivalent Climatology
Near-Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent
Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 4
TOVS Pathfinder Path-P Daily and Monthly Polar Gridded Atmospheric Parameters
SMAP L1C Radiometer Half-Orbit 36 km EASE-Grid Brightness Temperatures (SPL1CTB)
SMAP Enhanced L1C Radiometer Half-Orbit 9 km EASE-Grid Brightness Temperatures (SPL1CTB_E)
SMAP L2 Radar Half-Orbit 3 km EASE-Grid Soil Moisture (SPL2SMA)
SMAP L2 Radar/Radiometer Half-Orbit 9 km EASE-Grid Soil Moisture (SPL2SMAP)
SMAP L2 Radiometer Half-Orbit 36 km EASE-Grid Soil Moisture (SPL2SMP)
SMAP Enhanced L2 Radiometer Half-Orbit 9 km EASE-Grid Soil Moisture (SPL2SMP_E)
SMAP L3 Radar Northern Hemisphere Daily 3 km EASE-Grid Freeze/Thaw State (SPL3FTA)
SMAP L3 Radiometer Northern Hemisphere Daily 36 km EASE-Grid Freeze/Thaw State (SPL3FTP)
SMAP Enhanced L3 Radiometer Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State (SPL3FTP_E)
SMAP L3 Radar Global Daily 3 km EASE-Grid Soil Moisture (SPL3SMA)
SMAP L3 Radar/Radiometer Global Daily 9 km EASE-Grid Soil Moisture (SPL3SMAP)
SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture (SPL3SMP)
SMAP Enhanced L3 Radiometer Global Daily 9 km EASE-Grid Soil Moisture (SPL3SMP_E)
SMAP L4 Global Daily 9 km Carbon Net Ecosystem Exchange (SPL4CMDL)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM)
Description This program, currently at Version 0.3, contains routines to convert between latitude/longitude and row/column coordinates for both EASE-Grid and EASE-Grid2.0.
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Tool Name ezlhconv.c

(With header file, ezlhconv.h, for data set users with knowledge of C programming)
Tool Type C
Applicable Data Sets AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua 5-Day L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Monthly L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Daily L3 Surface Soil Moisture, Interpretive Parms, & QC EASE-Grids
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Global Monthly EASE-Grid Snow Water Equivalent Climatology
Near-Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent
Description Subroutines in these files can be called from the user's main program, to convert between latitude/longitude and row/column coordinates.
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Tool Name ezlhconv.f

(For data set users with knowledge of FORTRAN programming)
Tool Type FORTRAN
Applicable Data Sets AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua 5-Day L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Monthly L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Daily L3 Surface Soil Moisture, Interpretive Parms, & QC EASE-Grids
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Global Monthly EASE-Grid Snow Water Equivalent Climatology
Near-Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent
Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 3
Description Subroutines in these files can be called from the user's main program, to convert between latitude/longitude and row/column coordinates.
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Geolocation Data Files 

For data set users who only have the need of the latitude and longitude of the center of any cell in the grid, the following geolocation data file is available.

Tool Name

gridloc.EASE2_HXXkm.tgz

The following table explains the file naming convention used for this geolocation data file:
Where:

Variable
Description
gridloc Grid location
EASE2 Projection
H Hemisphere:
N (north)
S (south)
M (global)
XX Resolution in kilometers (km)
.tgz GZIP Compressed Tar Archive file
Tool Type Geolocation Data Files
Applicable Data Sets Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice
MEaSUREs Northern Hemisphere Terrestrial Snow Cover Extent Daily 25km EASE-Grid 2.0
MEaSUREs Northern Hemisphere Terrestrial Snow Cover Extent Weekly 100km EASE-Grid 2.0
MEaSUREs Arctic Sea Ice Characterization Daily 25km EASE-Grid 2.0
MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0
MEaSUREs Northern Hemisphere State of Cryosphere Daily 25km EASE-Grid 2.0
MEaSUREs Northern Hemisphere State of Cryosphere Weekly 100km EASE-Grid 2.0
SMAP L1C Radiometer Half-Orbit 36 km EASE-Grid Brightness Temperatures (SPL1CTB)
SMAP Enhanced L1C Radiometer Half-Orbit 9 km EASE-Grid Brightness Temperatures (SPL1CTB_E)
SMAP L2 Radar Half-Orbit 3 km EASE-Grid Soil Moisture (SPL2SMA)
SMAP L2 Radar/Radiometer Half-Orbit 9 km EASE-Grid Soil Moisture (SPL2SMAP)
SMAP L2 Radiometer Half-Orbit 36 km EASE-Grid Soil Moisture (SPL2SMP)
SMAP Enhanced L2 Radiometer Half-Orbit 9 km EASE-Grid Soil Moisture (SPL2SMP_E)
SMAP L3 Radar Northern Hemisphere Daily 3 km EASE-Grid Freeze/Thaw State (SPL3FTA)
SMAP L3 Radiometer Northern Hemisphere Daily 36 km EASE-Grid Freeze/Thaw State (SPL3FTP)
SMAP Enhanced L3 Radiometer Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State (SPL3FTP_E)
SMAP L3 Radar Global Daily 3 km EASE-Grid Soil Moisture (SPL3SMA)
SMAP L3 Radar/Radiometer Global Daily 9 km EASE-Grid Soil Moisture (SPL3SMAP)
SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture (SPL3SMP)
SMAP Enhanced L3 Radiometer Global Daily 9 km EASE-Grid Soil Moisture (SPL3SMP_E)
SMAP L4 Global Daily 9 km Carbon Net Ecosystem Exchange (SPL4CMDL)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP)
SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM)
Description

The gridloc.*.tgz files contain two files with latitude and longitude geolocation data respectively. Files are flat binary, in row-major order, beginning with the upper left pixel of the grid and proceeding across the top row, etc. Data are double-precision 8-byte floating point values. The geolocation values indicate the position of the center of each pixel in degrees. Fill value is -999.0.

GRID_NAME.[lats|lons].COLSxROWSx1.double

Where:

Variable
Description
GRID_NAME EASE-Grid 2.0 projection. For example, EASE2_N25km.
lats|lons Contents are either latitude or longitude at each pixel.
COLS Columns in the array.
ROWS Rows in the array.
1 One data element per pixel.
.double Data are double-precision 8-byte floating point.
Grid Name EASE2_N, EASE2_S, EASE2_M
Coverage North, South, Global
Resolultion Varies
Dimensions Varies
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This section explains the file naming convention used for the following geolocation data files.

These geolocation files contain flat, binary arrays of 4-byte integers containing the latitude or longitude of the respective grid cell in hundred-thousandth degrees. The user should divide the stored integer value by 100,000. to yield decimal degrees, with 1 meter precision. The user is expected to know which byte-ordering convention is required by their system. Files are provided in PC (little-endian/LSB) byte orders.

Depending on the coverage area, which varies for different grids (such as ML, NH, SL, Sa25 and so on), scaled latitudes range from -90.00000 to 90.00000, and scaled longitudes range from -180.00000 to 180.00000 with missing data (such as corners of grids with hemispheric coverage) indicated by scaled value 14316.55765.

Example file name: MLLATLSB

ggpppooo

Where:

Variable Description
gg Grid name (NL, NH, SL, SH, ML, MH, NAARI, Na25, Sa25)
ppp Parameter (LAT, LON)
ooo Byte order:
LSB: Least Significant Byte/litte-endian
MSB: Most Significant Byte/big-endian1
1As of January 2012, EASE-Grid geolocation files are no longer provided in MSB byte order.
Tool Names MLLATooo and MLLONooo
Tool Type Geolocation Data Files
Applicable Data Sets AMSR-E/Aqua Daily L3 Surface Soil Moisture, Interpretive Parms, & QC EASE-Grids
AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name ML
Coverage Global
Resolution 25 km
Dimensions 1383 x 586 pixels
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Tool Names MHLATooo and MHLONooo
Tool Type Geolocation Data Files
Applicable Data Sets DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name MH
Coverage Global
Resolution 12.5 km
Dimensions 2766 x 1171 pixels
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Tool Names NLLATooo and NLLONooo
Tool Type Geolocation Data Files
Applicable Data Sets DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua 5-Day L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Monthly L3 Global Snow Water Equivalent EASE-Grids
Global Monthly EASE-Grid Snow Water Equivalent Climatology
Near-Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent
Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 3
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name NL
Coverage Northern Hemisphere
Resolution 25 km
Dimensions 721 x 721 pixels
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Tool Names NHLATooo and NHLONooo
Tool Type Geolocation Data Files
Applicable Data Sets DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name NH
Coverage Northern Hemisphere
Resolution 12.5 km
Dimensions 1441 x 1441 pixels
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Tool Names SLLATooo and SLLONooo
Tool Type Geolocation Data Files
Applicable Data Sets AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
Global Monthly EASE-Grid Snow Water Equivalent Climatology
AMSR-E/Aqua Daily L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua 5-Day L3 Global Snow Water Equivalent EASE-Grids
AMSR-E/Aqua Monthly L3 Global Snow Water Equivalent EASE-Grids
Near-Real-Time SSM/I EASE-Grid Daily Global Ice Concentration and Snow Extent
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name SL
Coverage Southern Hemisphere
Resolution 25 km
Dimensions 721 x 721 pixels
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Tool Names SHLATooo and SHLONooo
Tool Type Geolocation Data Files
Applicable Data Sets DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name SH
Coverage Southern Hemisphere
Resolution 12.5 km
Dimensions 1441 x 1441 pixels
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Tool Names NAARILATooo and NAARILONooo
Tool Type Geolocation Data Files
Applicable Data Sets AARI 10-Day Arctic Ocean EASE-Grid Sea Ice Observations
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name NAARI
Coverage Subset of the Northern Hemisphere
Resolution 25 km
Dimensions 721 x 721 pixels
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Tool Names Na25LATooo and Na25LONooo
Tool Type Geolocation Data Files
Applicable Data Sets Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors
National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format
AVHRR Polar Pathfinder Twice-Daily 25 km EASE-Grid Composites
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name Na252
Coverage Subset of the Northern Hemisphere
Resolution 25 km
Dimensions The Na25 EASE-Grid is a subset of the 25 km Northern Hemisphere Azimuthal EASE-Grid, including the center 361 columns by 361 rows, with the North Pole at the center of the center-most grid cell. For a complete grid description, please refer to the Summary of NOAA/NASA Polar Pathfinder Grid Relationships Web page.
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Tool Names Sa25LATooo and Sa25LONooo
Tool Type Geolocation Data Files
Applicable Data Sets Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors
National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format
AVHRR Polar Pathfinder Twice-Daily 25 km EASE-Grid Composites
Description Provides latitude and longitude for the center of any cell in the grid. For additional details, please refer to the Geolocation Data Files section of this Web page.
Grid Name Sa252
Coverage Subset of the Southern Hemisphere
Resolution 25 km
Dimensions The Sa25 EASE-Grid is a subset of the 25 km Northern Hemisphere Azimuthal EASE-Grid, including the center 321 columns by 321 rows, with the North Pole at the center of the center-most grid cell. For a complete grid description, please refer to the Summary of NOAA/NASA Polar Pathfinder Grid Relationships Web page.
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Additional Tools for EASE-Grid

Geolocating EASE-Grid Data in ENVI

The Geolocating EASE-Grid Data in ENVI document describes how to geolocate North, South, and Global EASE-Grid data from the DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures product using ENVI Software.

Importing Passive Microwave EASE-Grid Data into a ArcGIS

The Importing NSIDC Passive Microwave EASE-Grid Data into ArcGIS document describes how to import Passive Microwave EASE-Grid data into ArcGIS.

Polar Stereographic Data Tools

The software and tools are grouped into the following categories:

  • Data Extraction Tools: The data extraction tools allow the user to extract and read the data from the data files.
  • Data Display Tools: The data display tools allow the user to display data from the data files in various ways.
  • Geocoordinate and Pixel-Area Tools: The Geocoordinate tools allow the user to obtain latitude/longitude coordinates from (i,j) coordinates and vice versa. The pixel-area tools allow the user to obtain the area of a given pixel.
  • Masks and Overlays: NSIDC provides land, region, and ocean masks and overlays that can be applied to the polar stereographic data files.

Data Extraction Tools

Tool Name extract.pro
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Description IDL program that allows you to open a brightness temperature grid file and read it into an array, making it available for further manipulation in IDL or to write to hard disc. After the program has read the user-indicated time range, an array is returned with a 2-byte integer array of brightness temperatures expressed in tenths of a kelvin (0.1 K). For example, a value of 2358 translates to 235.8 K.
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Usage Example IDL Routines for Passive Microwave Data: Usage Examples - extract.pro

Tool Name extract_ice.pro
Applicable Data Sets Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Description IDL program that extracts a time series of polar sea ice data. The extraction routine works on both the daily and monthly sea ice files allowing users to select and display sea ice concentrations. For monthly data, users may select which image threshold to view (0, 5, 10, or 15% ice cut off).
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Usage Example IDL Routines for Passive Microwave Data: Usage Examples - extract_ice.pro

Data Display Tools

Tool Name dataviewer.tar.gz 
Applicable Data Sets
Polar Stereographic Projection
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
 
EASE-Grid Projection
Near-Real-Time SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent Version 4
 
Quarter-Degree Projection
AMSR-E/Aqua Daily Global Quarter-Degree Gridded Brightness Temperatures
Description The NSIDC DataViewer is an interactive tool for viewing and displaying satellite images from select NSIDC passive microwave data sets. Images in PNG, JPEG, TIFF, and other commonly used image data formats can also be viewed and displayed in a user-defined grid.

Up to 64 images can be displayed simultaneously in the DataViewer resizeable graphics window, allowing data users to page through a series of images. Images can be scaled and manipulated either individually or as a group. By moving the cursor over an image, a data user can obtain the latitude and longitude coordinates as well as the image value at the cursor location. After an image or series of images is manipulated, the contents of the graphics window(s) can be saved in a variety of image formats, including PostScript, PNG, JPEG, and TIFF.

The DataViewer is a program written in Interactive Data Language (IDL). It can be run in IDL with an IDL license, via the freely distributed IDL Virtual Machine, or as a run-time application.

Please Note:
  • DataViewer produces a scaling error with time values in DMSP-F17 SSMIS time (.tim) files. When using SSMIS .tim files, please be advised that data points will display as 1/10th of their actual value.
  • DataViewer is currently incompatible with data obtained using the Polaris search and subsetter tool.
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Tool Name display_onset_of_melt.pro
Applicable Data Sets Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
Description IDL program that allows the user to view the data in graphical form.
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Geocoordinate and Pixel-Area Tools

The geocoordinate and pixel-area tools described here provide the same functionality for all polar stereographic passive microwave data sets at NSIDC. They include Fortran routines for determining latitude and longitude from i,j coordinates and a pixel-area grid.


Geocoordinate Tools

The following geocoordinate tools are available:

Tool Name dataviewer.tar.gz 
Applicable Data Sets
Polar Stereographic Projection
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
 
EASE-Grid Projection
Near-Real-Time SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures
Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures
AMSR-E/Aqua Daily EASE-Grid Brightness Temperatures
Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent Version 4
 
Quarter-Degree Projection
AMSR-E/Aqua Daily Global Quarter-Degree Gridded Brightness Temperatures
Description The NSIDC DataViewer is an interactive tool for viewing and displaying satellite images from select NSIDC passive microwave data sets. Images in PNG, JPEG, TIFF, and other commonly used image data formats can also be viewed and displayed in a user-defined grid.

Up to 64 images can be displayed simultaneously in the DataViewer resizeable graphics window, allowing data users to page through a series of images. Images can be scaled and manipulated either individually or as a group. By moving the cursor over an image, a data user can obtain the latitude and longitude coordinates as well as the image value at the cursor location. After an image or series of images is manipulated, the contents of the graphics window(s) can be saved in a variety of image formats, including PostScript, PNG, JPEG, and TIFF.

The DataViewer is a program written in Interactive Data Language (IDL). It can be run in IDL with an IDL license, via the freely distributed IDL Virtual Machine, or as a run-time application.

Please Note:
  • DataViewer produces a scaling error with time values in DMSP-F17 SSMIS time (.tim) files. When using SSMIS .tim files, please be advised that data points will display as 1/10th of their actual value.
  • DataViewer is currently incompatible with data obtained using the Polaris search and subsetter tool.
Access FTP

Tool Name locate.for
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description Fortran executable that allows the user to enter an (i, j) coordinate, obtain the corresponding latitude/longitude coordinate, and vice versa. This executable must be run with the subroutines mapll.for and mapxy.for.
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name mapll.for and mapxy.for
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description Subroutines that are associated with the Fortran executable, locate.for. These programs need to be compiled but are not run explicitly. They are called by locate.for; thus, the user should compile these programs with locate.for, and then use locate to do the conversions.
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name psn06lats_v3.dat and pss06lats_v3.dat (Note on Versions)1
Applicable Data Sets AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
Description Grids that determine the latitude of a given pixel for the 6.25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). These latitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the latitude value at the center of the corresponding data grid cells.

psn06lats_v3.dat: 1216 columns x 1792 rows, range = [31.011, 89.959]
pss06lats_v3.dat: 1264 columns x 1328 rows, range = [-39.264, -89.959]
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Tool Name psn06lons_v3.dat and pss06lons_v3.dat (Note on Versions)1
Applicable Data Sets AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
Description Grids that determine the longitude of a given pixel for the 6.25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemispere). These longitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the longitude value at the center of the corresponding data grid cells. An East-longitude convention is used; therefore, positive longitude values are to the east of Greenwich, England.

psn06lons_v3.dat: 1216 columns x 1792 rows, range = [-180.000, 179.953]
pss06lons_v3.dat: 1264 columns x 1328 rows, range = [-179.955, 179.955]
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Tool Name psn12lats_v3.dat and pss12lats_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
Description Grids that determine the latitude of a given pixel for the 12.5 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). These latitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the latitude value at the center of the corresponding data grid cells.

psn12lats_v3.dat: 608 columns x 896 rows, range = [31.041, 89.918]
pss12lats_v3.dat: 632 columns x 664 rows, range = [-39.297, -89.918]
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name psn12lons_v3.dat and pss12lons_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
Description Grids that determine the longitude of a given pixel for the 12.5 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). These longitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the longitude value at the center of the corresponding data grid cells. An East-longitude convention is used; therefore, positive longitude values are to the east of Greenwich, England.

psn12lons_v3.dat: 608 columns x 896 rows, range = [-180.000, 179.907]
pss12lons_v3.dat: 632 columns x 664 rows, range = [-179.909, 179.909]
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name psn25lats_v3.dat and pss25lats_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description Grids that determine the latitude of a given pixel for the 25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). These latitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the latitude value at the center of the corresponding data grid cells.

psn25lats_v3.dat: 304 columns x 448 rows, range = [31.102, 89.836]
pss25lats_v3.dat: 316 columns x 332 rows, range = [-39.364, -89.836]
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name psn25lons_v3.dat and pss25lons_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description Grids that determine the longitude of a given pixel for the 25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). These longitude grids are in binary format and are stored as 4-byte integers (little endian) scaled by 100,000 (divide the stored value by 100,000 to get decimal degrees). Each array location (i, j) contains the longitude value at the center of the corresponding data grid cells. An East-longitude convention is used; therefore, positive longitude values are to the east of Greenwich, England.

psn25lons_v3.dat: 304 columns x 448 rows, range = [-180.000, 179.814]
pss25lons_v3.dat: 316 columns x 332 rows, range = [-179.818, 179.818]
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP


Pixel-Area Grids

The following pixel-area tools are availabe:

Please note that the data ranges given here are latitude and longitude values for the center of each grid cell. The range covered by the full grid extends to the pole (90 degrees latitude) and all longitudes (0 to 360 degrees longitude). Also note that corrected grids for the northern hemisphere were created June 22, 1999 and should replace the three psn25*.dat files that were distributed prior to this date.

To determine the lat/lon values of corresponding (i,j) data grid cells:

  1. Read in the array as long (4-byte) integers.
  2. Divide these values by 100,000. The resulting array gives the lat/lon values for the data grid cells in decimal degree

Tool Name psn06area_v3.dat and pss06area_v3.dat (Note on Versions)1
Applicable Data Sets AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
Description Grids that determine the area of a given pixel for the 6.25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). The arrays are in binary format and are stored as 4-byte integers scaled by 1000 (divide by 1000 to get square km).

psn06lons_v3.dat: 1216 columns x 1792 rows
pss06lons_v3.dat: 1264 columns x 1328 rows
Access FTP

Tool Name psn12area_v3.dat and pss12area_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
Description Grids that determine the area of a given pixel for the 12.5 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). The arrays are in binary format and are stored as 4-byte integers scaled by 1000 (divide by 1000 to get square km).

psn12area_v3.dat: 608 columns x 896 rows
pss12area_v3.dat: 632 columns x 664 rows
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name psn25area_v3.dat and pss25area_v3.dat (Note on Versions)1
Applicable Data Sets DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Nimbus-5 ESMR Polar Gridded Sea Ice Concentrations
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS
Near Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
Near-Real-Time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations
Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures
AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description Grids that determine the area of a given pixel for the 25 km grids for either hemisphere (psn for the Northern Hemisphere and pss for the Southern Hemisphere). The arrays are in binary format and are stored as 4-byte integers scaled by 1000 (divide by 1000 to get square km).

psn25area_v3.dat: 304 columns x 448 rows
pss25area_v3.dat: 316 columns x 332 rows
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

1 Version 3 (V3) pixel area files, developed by the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC), provide a more accurate mapping of area for the polar stereographic grid. V3 and V2 area files differ by a maximum of approximately 0.5 sq km per grid cell at the corners of the grid. The effect on total extent and total area estimates is, at most, 10,000 sq km (approximately ~0.1%).

The masks and overlays provided here supply the user with many options for concealing unwanted regions or overlaying coastlines and latitude/longitude grids; they are divided into the following categories:


Land Masks

The land masks are useful for concealing the land of the Northern and Southern Hemispheres prior to processing of the data. The files are divided into two categories: Northern Hemisphere and Southern Hemisphere.

Note on Land Masks

Several versions of the land masks have been developed, though NSIDC only distrubutes the most current masks.

Beginning with the SMMR era, the first masks NSIDC developed were landmask.ntb and landmask.stb. Other masks were later added for use with SSM/I F8 data. The last set of masks to be added to the series are those beginning with gsfc, which were originally developed for use with SSM/I F11 and F13. However, all of the masks provided here will work across all platforms (SMMR and SSM/I).

The relatively slight differences in numbers of SSM/I-grid pixels masked as land can introduce discrepancies in analyses of time series spanning the SMMR and SSM/I period. One method of addressing this issue is to generate a composite mask in which all pixels mapped as land in any of the masks are coded as land pixels in the composite mask. Use of such a composite mask improves the consistency of the SMMR and SSM/I record at the expense of masking additional ocean areas as land. A composite of the CIA World Data Bank I and II (GSFC-1 and JPL-1) has been produced by J. Maslanik at NSIDC.

Another issue is the effect of contamination of coastal ocean pixels by their proximity to land. Such proximity can modify the brightness temperatures of coastal ocean pixels, producing false ice concentration values along some coasts. These pixel mixing errors are considered in the summer 1996 issue of NSIDC Notes (Issue no. 18). Maslanik et al. (1996) discuss the effects of such land contamination in introducing differences between SMMR and SSM/I time series, and they describe the use of a modified land mask where land areas are extended to mask substantial contamination. The Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I Brightness Temperatures land mask (n3blcmsk.hdf) alleviates this problem whereby ocean pixels adjacent to land or one pixel removed from land are designated as land-contaminated.

The land masks that are availabe are the following:

Tool Name amsr_gsfc_6n.hdf and amsr_nic_6s.hdf
Applicable Data Sets AMSR-E/Aqua Daily L3 6.25 km 89 GHz Brightness Temperature Polar Grids
Description 6.25 km AMSR-E land mask for the Northern Hemisphere (amsr_gsfc_6n.hdf) and the Southern Hemisphere (amsr_nic_6s.hdf). The North land mask has not been updated since 1997. The South land mask includes an updated ice shelf definition created by the National Ice Center Science Department in June 2011 and an updated shoreline developed from ENVISAT and RADARSAT imagery from October 2009 to April 2010.

A 1-byte integer array is included in each HDF file.

amsr_gsfc_6n.hdf: 1216 columns x 1792 rows
Values are 0 (water), 3 (coast), 216 (land)
amsr_nic_6s.hdf: 1264 columns x 1328 rows
Values are 0 (water), 1 (land), 2 (coast)

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Tool Name amsr_gsfc_12n.hdf and amsr_nic_12s.hdf
Applicable Data Sets AMSR-E/Aqua Daily L3 12.5 km Brightness Temperature, Sea Ice Concentration, & Snow Depth Polar Grids
Description 12.5 km AMSR-E land mask for the Northern Hemisphere (amsr_gsfc_12n.hdf) and the Southern Hemisphere (amsr_nic_12s.hdf). The North land mask is identical to gsfc_12n.msk and was last updated in 1997. The South land mask includes an updated ice shelf definition created by the National Ice Center Science Department in June 2011 and an updated shoreline developed from ENVISAT and RADARSAT imagery from October 2009 to April 2010.

A 1-byte integer array is included in each HDF file.

amsr_gsfc_12n.hdf: 608 columns x 896 rows
Values are 0 (water) and 1 (land).
amsr_nic_12s.hdf: 632 columns x 664 rows
Values are 0 (water), 1 (land), and 2 (coast).

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Tool Name amsr_gsfc_25n.hdf and amsr_nic_25s.hdf
Applicable Data Sets AMSR-E/Aqua Daily L3 25 km Brightness Temperature & Sea Ice Concentration Polar Grids
Description 25 km AMSR-E land mask for the Northern Hemisphere (amsr_gsfc_25n.hdf) and the Southern Hemisphere (amsr_nic_25s.hdf). The North land mask is identical to gsfc_25n.msk and was last updated in 1997. The South land mask includes an updated ice shelf definition created by the National Ice Center Science Department in June 2011 and an updated shoreline developed from ENVISAT and RADARSAT imagery from October 2009 to April 2010.

A 1-byte integer array is included in each HDF file.

amsr_gsfc_25n.hdf: 304 columns x 448 rows
Values are 0 (water) and 1 (land).
amsr_nic_25s.hdf: 316 columns x 332 rows
Values are 0 (water), 1 (land) and 2 (coast).

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Tool Name gsfc_12n.msk and gsfc_12s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Description 12.5 km land and coast mask for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). A 1-byte integer array is included in each file. Values are 0 or 1, where 1 is the mask.

gsfc_12n.msk: 608 columns x 896 rows
gsfc_12s.msk: 632 columns x 664 rows
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Tool Name gsfc_25n.msk and gsfc_25s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Description 25 km land and coast mask for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). A 1-byte integer array is included in each file. Values are 0 or 1, where 1 is the mask.

gsfc_25n.msk: 304 columns x 448 rows
gsfc_25s.msk: 316 columns x 332 rows
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name landmask.ntb and landmask.stb
Applicable Data Sets Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Description Northern (ntb) and Southern (stb) Hemisphere land mask at a 25 km resolution. Note: These have been superseded by the gsfc_25n.msk and gsfc_25s.msk but may be more appropriate for the ESMR data sets.

landmask.ntb: 304 columns x 448 rows
landmask.stb: 316 columns x 332 rows
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Tool Name n3blcmsk.hdf
Applicable Data Sets Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I Brightness Temperatures
Description Northernth Hemisphere, 25 km land mask. Ocean pixels adjacent to land or one pixel removed from land are designated as land-contaminated.

304 columns x 448 rows
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Tool Name pole_n.msk
Applicable Data Sets Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Description Circular mask that symmetrically covers the observed maximum extent of the missing data (resulting from the orbit inclination and instrument swath) near the North Pole. This is a 1-byte array with no header. The area of the SSM/I hole has a value of 1. The additional area of the SMMR hole (a ring around the SSM/I hole) has a value of 2. All other pixels have a value of 0.

pole_n.msk: 304 columns x 448 rows
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Land Overlays

The land overlays are useful for overlaying coast line and latitude/longitude grids on top of images and processed data. The files are broken down into two categories: Northern Hemisphere and Southern Hemisphere.

The land overlays that are availabe are the following:

Tool Name coast_12n.msk and coast_12s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Description 12.5 km coastline grid overlay for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). Format is 1-byte integer arrays. Values are 0 or 1, where 1 is the mask.

coast_12n.msk: 608 columns x 896 rows
coast_12s.msk: 632 columns x 664 rows
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Tool Name coast_25n.msk and coast_25s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Description 25 km coastline grid overlay for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). Format is 1-byte integer arrays. Values are 0 or 1, where 1 is the mask.

coast_25n.msk: 304 columns x 448 rows
coast_25s.msk: 316 columns x 332 rows
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP

Tool Name ltln_12n.msk and ltln_12s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Description 12.5 km latitude/longitude grid overlay for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). Format is 1-byte integer arrays. Values are 0 or 1, where 1 is the mask.

ltln_12n.msk: 608 columns x 896 rows
ltln_12s.msk: 632 columns x 664 rows
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Tool Name ltln_25n.msk and ltln_25s.msk
Applicable Data Sets DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Nimbus-5 ESMR Polar Gridded Brightness Temperatures
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Brightness Temperatures
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Description 25 km latitude/longitude grid overlay for both hemispheres (n: Northern Hemisphere, s: Southern Hemisphere). Format is 1-byte integer arrays. Values are 0 or 1, where 1 is the mask.

ltln_25n.msk: 304 columns x 448 rows
ltln_25s.msk: 316 columns x 332 rows
Access Brightness Temperature Data Sets: FTP
Sea Ice Data Sets: FTP


Missing Data Mask

The circular section over the Northern Hemisphere pole (known as the pole hole) is never measured due to orbit inclination. The following mask is available for the pole hole region not covered by the SMMR and SSM/I instruments.
 

Tool Name pole_n.msk
Applicable Data Sets Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Description Circular mask that symmetrically covers the observed maximum extent of the missing data (resulting from the orbit inclination and instrument swath) near the North Pole. This is a 1-byte array with no header. The area of the SSM/I hole has a value of 1. The additional area of the SMMR hole (a ring around the SSM/I hole) has a value of 2. All other pixels have a value of 0.

pole_n.msk: 304 columns x 448 rows
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Region Masks

The region masks are smaller areas than the land masks although they can be used as land masks using the pixel value of 11.
 

Tool Name region_n.msk and region_s.msk
Applicable Data Sets Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I
Near Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations
Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS
Description Region masks for the Northern (n) and Southern (s) Hemisperes. The files contain a 300-byte header, followed by a two-dimensional byte array stored by rows in column order. Regions are assigned different pixel values as shown in the following table. The methods and sources for how these regions were geographically defined are discussed in Parkinson and Cavalieri (2012), Cavalieri and Parkinson (2008), and Parkinson et al. (1999).

region_n.msk: 448 rows x 304 columns
region_s.msk: 316 rows x 332 columns

Regions are assigned different byte values as follows:
 
Pixel Value Arctic Region Antarctic Region
1
Non-regional ocean
2
Sea of Okhotsk and Japan Weddell Sea
3
Bering Sea Indian Ocean
4
Hudson Bay Pacific Ocean
5
Baffin Bay/Davis Strait/Labrador Sea Ross Sea
6
Greenland Sea Bellingshausen Amundsen Sea
7
Kara and Barents Seas
8
Arctic Ocean
9
Canadian Archipelago
10
Gulf of St. Lawrence
11
Land Land
12
Coast Coast
0
Lakes, extended coast
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Ocean Masks

Tool Name For a full list of ocean masks and maximum extent masks, refer to the Monthly Ocean Masks and Maximum Extent Masks Web page.
Applicable Data Sets Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
Sea Ice Trends and Climatologies from SMMR and SSM/I
Description Monthly Ocean Masks and Maximum Extent Masks are available for the Northern (n) and Southern (s) Hemispheres. For more information and a description of the files, refer to the Monthly Ocean Masks and Maximum Extent Masks Web page.
 
Access See the Data Access section of the Monthly Ocean Masks and Maximum Extent Masks Web page for FTP access.