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\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename gtviewer.info
@include version.texi
@settitle GeoTIFF Viewer @value{VERSION}
@c %**end of header
@copying
This manual is for GeoTIFF Viewer (version @value{VERSION},
@value{UPDATED}).
Copyright @copyright{} 2006-2012 Jonathan duSaint.
@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled ``GNU Free
Documentation License.''
@end quotation
@end copying
@dircategory Image Viewers
@direntry
* GeoTIFF Viewer:: Viewer for GeoTIFF files.
@end direntry
@titlepage
@title GeoTIFF Viewer
@subtitle for version @value{VERSION}, @value{UPDATED}
@author Jonathan duSaint (@email{jon@@rockgeeks.net})
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage
@contents
@ifnottex
@node Top
@top GeoTIFF Viewer
@insertcopying
@end ifnottex
@menu
* About GeoTIFFs:: A quick introduction to GeoTIFFs for the uninitiated.
* Loading a GeoTIFF:: How to load a GeoTIFF into GeoTIFF Viewer.
* Navigating:: How to move around the image and zoom.
* Coordinate Systems:: Viewing different coordinate systems.
* Copying This Manual:: How to make copies of this manual
* Index:: Index of terms.
@end menu
@node About GeoTIFFs
@chapter About GeoTIFFs
@cindex chapter, first
@cindex TIFF
@cindex GeoTIFF
@cindex DRG
A @dfn{TIFF} (Tag Image File Format) is a flexible image type in which
all metadata is stored within the image as tags instead of in fixed
positions within an image header. A @dfn{GeoTIFF} is simply a TIFF
that has had tags added to allow georeferencing of the image.
Generally the additional tags will be in two categories. One set
describes the coordinate system in use. The other gives image
specific information with respect to the coordinate system.
California @dfn{DRG}s (Digital Raster Graphics), for example, define
the California coordinate system, which is based on NAD27 or NAD84,
uses Albers Equal Area Projection, and is in meters offset from a
known latitude and longitude. California DRGs then have the corners
georeferenced in meters within the coordinate system and have a pixel
value, where the distance between each pixel is a certain number of
meters.
For further information on GeoTIFFs, see
@url{http://www.remotesensing.org/geotiff/geotiff.html,the GeoTIFF
home page}. California also has @url{http://gis.ca.gov, an official
GIS page with much information and links to data}.
@node Loading a GeoTIFF
@chapter Loading a GeoTIFF
@cindex chapter, second
@cindex file, loading
@cindex loading a file
@cindex USGS
@cindex GeoTIFFs, obtaining
@cindex obtaining GeoTIFFs
To load a GeoTIFF into GeoTIFF Viewer, select Open from the File menu.
Then navigate to the directory where your GeoTIFFs are stored and
select the image to view. The image is then loaded and the details of
the coordinate system are handled by the software.
@url{http://www.usgs.gov, The USGS} is the producer for DRGs at
various scales for the entire United States with the exception of the
areas covered by California or the Tennessee Valley Authority, which
produce their own. California DRGs may be freely downloaded at
@url{http://gis.ca.gov/casil/gis.ca.gov/drg/, the CaSIL DRG file
directory}.
@node Navigating
@chapter Navigating
@cindex chapter, third
@cindex scrolling
@cindex panning
@cindex zooming
The mouse is used for all image navigation within GeoTIFF Viewer. To
pan the image, simply click and drag the image. Scrolling up with the
mouse wheel zooms the image in. Scrolling down with the mouse wheel
zooms the image out. To zoom back to the default scale, double click.
Beware of zooming in too far or too fast, the image data is kept in
memory, and, owing to the size of most DRGs, can become quite unwieldy
when zoomed in too far.
@node Coordinate Systems
@chapter Coordinate Systems
@cindex chapter, fourth
@cindex geocoordinate display
@cindex image coordinate display
@cindex pixel display
GeoTIFF viewer allows for different types of units for the display of
the mouse coordinates. All three options are available from the View
menu. The default mode is geocoordinates, where the the mouse
coordinates are displayed in latitude and longitude. In image
coordinate display mode, the native coordinate system of the GeoTIFF
is used. For California DRGs, this is in meters offset from a known
latitude and longitude. The last display mode is pixels. This is
simply the pixel offset from the top left of the image.
@node Copying This Manual
@appendix Copying This Manual
@menu
* GNU Free Documentation License:: License for copying this manual
@end menu
@include fdl.texi
@node Index
@unnumbered Index
@printindex cp
@bye
|
