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EASE-Grid Data

Data Sets in the Equal-Area Scalable Earth Grid

Importing Passive Microwave EASE-Grid Data into a GIS

This Web page describes how to import passive microwave EASE-Grid data into ArcGIS. Follow the instructions for the appropriate version of EASE-Grid:


Instructions for Importing EASE-Grid 2.0 Data

The following steps were tested with ArcGIS 10 on a Windows platform.

1. Rename data file

Data files from Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent are available via FTP and are distributed in binary format with a .bin file extension. In order to be able to import one of these data files into ArcGIS, you will need to:
Rename the file extension from .bin to .bsq (band-sequential).

Example: EASE2_N25km.snowice.20101220-20101226.v04.bsq

2. Create a header file

In a text editor, create a new file with the content below. You will need to give the file the same name as the data file, but with a .hdr extension. Make sure that the .bsq file and the .hdr file are saved in the same folder and are accessible to ArcGIS.

Content of the header file (copy and paste the following):
nrows 720 
ncols 720 
nbands 1 
nbits 8 
layout bsq 
byteorder I 
ulxmap -8987500 
ulymap 8987500 
xdim 25000 
ydim 25000

Example header file name: EASE2_N25km.snowice.20101220-20101226.v04.hdr

3. Convert the file to an ESRI-compatible grid format

Open ArcMap, and in ArcToolbox choose Conversion Tools > To Raster > Raster To Other Format (multiple).
In the dialogue box that opens, select your .bsq file as the Input Raster. Choose a location in the Output Workspace and choose TIFF as the Raster Format.
Click OK. The program will use your .hdr file to define your input raster and create a new, ESRI-compatible file.

ArcToolbox drop-down menu screen shot Raster To Other Format window screenshot

4. Define the projection for the new grid file

Choose ArcToolbox > Data Management Tools > Projections and Transformations > Define Projection.
In the dialogue box that opens, choose your .bsq file as the Input Dataset or Feature Class.
Next, click the button to the right of the Coordinate System input field.
In the dialogue box that opens, click New > Projected Coordinate System.
Enter a name of your choosing at the top of the next dialogue box.
In the Projection > Name drop-down menu, choose Lambert_Azimuthal_Equal_Area.

Next, fill in the form fields to match the parameters below:
false_easting: 0.000000 
false_northing: 0.000000 
central_meridian: 0.000000 
latitude_of_origin: 90.000000
Linear Unit: Meter
Meters per unit: 1

Under Geographic Coordinate System at the bottom of the dialogue box, click Select.
In the next dialogue box that opens, choose World > WGS 1984.prj. Click Add.
Then, click Finish and Ok until all the dialogue boxes are resolved.


The folllowing images show information contained in the Source tab of Layer Properties:

Information contained in the Source tab of Layer Properties

Layer Properties under Source Tab

Layer Properties under Source Tab

 

Visualizing the result:

Visualizing the result

 

Instructions for Importing Original EASE-Grid Data

This section describes how to import passive microwave EASE-Grid data into ArcGIS. For importing EASE-Grid 2.0 data into ArcGIS, refer to the Instructions for Importing EASE-Grid 2.0 Data section at the top of this Web page.

The following steps were tested with ArcGIS 9.x on a Windows platform.

1. Rename data file

Data files from DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures and Nimbus-7 SMMR Pathfinder Daily EASE-Grid Brightness Temperatures are compressed with the gzip utility and available via FTP. You will notice the file name has no extension. Extract the data file to your computer and rename it to include a .bsq (band-sequential) file extension.

2. Create a header file

Create an ASCII header file with the same name as your data file, but with an .hdr extension. (If you ordered subsetted EASE-Grid data from GISMO, the data package you received already contains at least one sample header file).

EASE-Grid data are available in high and low resolutions, indicated by the file names. In the header file names, N represents North, S represents South, M represents Global, L indicates 25 km resolution in SMMR and SSM/I data; and H indicates 12.5 km resolution, which is only used for the SSM/I 85 GHz channels.

Downloadable Header Files:
Header File Name Data Description
NH.hdr 12.5 km (high) resolution 16-bit SSM/I 85 GHz brightness temperature data
SH.hdr
MH.hdr
NL.hdr 25 km (low) resolution 16-bit data; all SMMR files, including time files; SSM/I brightness temperature files only
SL.hdr
ML.hdr
NLtime.hdr 25 km (low) resolution SSM/I (8-bit) time files only
SLtime.hdr
MLtime.hdr

3. Convert image to an ESRI compatible grid format

Start ArcMap and open ArcToolbox. Select Conversion Tools > To Raster > Raster to Other Format. The Raster to Other Format window will appear. In the Input Raster box, browse and select an EASE-Grid data file with a .bsq extension (Refer to Step 1). In the Output Workspace box, select the location to store the new data set. In the Output Format box, select the format to create the new data set; this can be one of three formats: ESRI Grid, ERDAS Imagine, or TIFF. Click OK.

ArcToolbox drop-down menu screen shot Raster To Other Format window screenshot

4. Define the projection for the new data set

In ArcToolbox, under Data Management Tools select Projections and Transformations > Define Projection. In the window that appears, select the newly created grid (Refer to Step 3) as the input data set. Next, select the button next to the coordinate system box. In the window that appears select New... > Projected.

In the new window, enter a custom projection name in the first box. Then, select the projection for your data set (Lambert_Azimuthal_Equal_Area for Northern and Southern Hemisphere data and Cylindrical Equal-Area for global data). Next, modify the projection parameters to match the following:

North False_Easting: 0.0
False_Northing: 0.0
Central_Meridian: 0.0
Latitude_Of_Origin: 90.0
South False_Easting: 0.0
False_Northing: 0.0
Central_Meridian: 0.0
Latitude_Of_Origin: -90.0
Global False_Easting: 0.0
False_Northing: 0.0
Central_Meridian: 0.0
Standard_Parallel_1: 30.0

Leave the Linear Units as meters and proceed to the Geographic Coordinate System box and select New.... In the new window, enter a new name, then assign the Datum to be <custom>. Leave the Spheroid option box as <custom> and in the Semimajor axis and Semiminor axis boxes, enter 6371228. Next, change Angular Units to Degrees and choose Greenwich for the Prime Meridian box. Before clicking OK in the final window, be sure to review and Save the newly created coordinate system so that other data sets can easily be reprojected to the new system. Click OK.

When overlaying other data, such as coastlines, be sure to reproject those data into the same projections as the EASE-Grid data.

Command Line Routines

The commands discussed here for converting and projecting EASE-Grid data can also be run at the command line in ArcGIS 9.x. To open the command line in ArcMap, select the command line icon.

Command line icon screenshot

After renaming the data to a .bsq file and creating a header file (Refer to steps 1 and 2) use the following command to convert the data into a compatible grid format:

RasterToOtherFormat <in_dataset; in_dataset; ...> <output_workspace> {GRID; IMAGINE IMAGE; TIFF}

Where <in_dataset> is the name of the EASE-Grid file to convert, <output_workspace> is the location to store the new data set, and {GRID; IMAGINE IMAGE; TIFF} is the format for the new raster data set.

The next step is to project the newly created raster data set. This can be accomplished with the following command:

DefineProjection_management <in_dataset> <coor_system>

Where <in_dataset> is the newly created data set and <coor_stystem> is the full path to the location of the appropriate .prj file created in Step 4.