Harvard Geospatial Library
Defining the Projection of your Downloaded Image

The ZIP file of the georeferenced map you downloaded contains the following
three files:
	
	<NAME1>.tif or <NAME1>.jp2	
	<NAME1>.tfw or <NAME1>.j2w
	<NAME1>.xml

(1) The .tif or .jp2 file is your raster image in TIFF or JPEG2000 format. 
(2) The .tfw or .j2w file is called a "world file" and holds geo-registration
data. 
>> Note: the image and world file should be stored in the same working
>> directory <<
(3) The .xml file is the metadata file containing descriptive information
about the data set including the data's projection (also referred to as the
projected coordinate system or spatial reference).  To retrieve the projection
information use one of the following:
a.) If using ESRI software, open ArcCatalog, highlight the <NAME1>.xml
metadata file in the catalog tree, select the Metadata tab, and scroll to the
"Spatial Reference Information" heading.  
b.) If you're viewing the raw xml file of the metadata, find the <spref> tag
and its sub-elements to identify the data's projection information.  
c.) You may also find this information on the HGL website via the "show
metadata" icon in your Harvard Geospatial Library search results.

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In order to display your image in a geospatial context with other projected
data, you will need to define the projection of the image. 

If you are using ESRI software, follow these steps:

A.) Go to Arc Toolbox > Data Management > Projections and Transformations >
Define Projection.
	1.) In the Input Dataset box, navigate to your input raster image.
	2.) In the Coordinate System box, navigate to the projected coordinate
system that is defined in the image's metadata. 

Note: It may be necessary to MODIFY the coordinate system in the Spatial
Reference Properties if there is a central meridian that is not standard (i.e.
a Mercator projection with a central meridian of 152 degrees instead of 0
degrees).  A non-standard central meridian will be defined in the Spatial
Reference Information of the metadata.

B.) You are now ready to display your image with other projected data or on
its own. 


If you have any questions please send us an email: hgl_ref@hulmail.harvard.edu