EMIS - UN-Habitat

Building an Environmental Management Information System
catalogues, JPEG (with extension), MrSID (with extension), National Image
Transfer Format (NITF) (with extension), Sun raster files,TIFF,TIFF/LZW
compressed.
Note: ArcView GIS does not rotate, or warp, images. If your world file
has non-zero rotation terms (D and B parameters), the image
may change its position relative to vector data in the same view
when you zoom or pan.
To register an image in ArcView 3.2 the script “register.avx” can help.This
extension can be found on the EMIS CD-ROM.This extension was created
to register aerial photos that are already ortho-rectified.This extension
works with jpg and bmp type images, as well as with tif, bsq, bip, bil and sun
image types.
This extension will create a world file for an image by picking control
points between the image and a projected feature theme.The first order fit
can shift the image up or down and stretch the image both vertically and
horizontally. Keep this in mind, because it will not “warp” or “rubber sheet”
the image.
1. To use this extension place it in your ext32 directory and from the
File -Extensions menu select the Image to Map World File Creator.
2. You should see a blue diamond on the Project Button Bar. Press this
button to begin and you will be asked for the name of the image you
want to create a World File for and the name of the Feature Theme you
want to register it to.
3. On the left side of your tool bar you will see a new tool that looks like
a flag. Choose this tool and with it pick Ground Control Points (GCP’s)
that have the same spatial location for both the image and the feature
theme,To do this, select a point on the image. Select a point on the
feature theme that is the same location.This constitutes 1 GCP pair.
4. Now continue: select a point on the image, select a point on the feature
theme that is the same location.
5. Continue doing this until you have at least 6 GCP pairs.
For a first order fit you need a minimum of 3 pairs. However, it is
recommended that you have twice the minimum, so the code is set
up so that you have to pick 6 pairs.
6. Once your GCP’s are chosen minimise the two views and open the
table called Ground Control Point Table.
This table has 6 fields:
Use Pnts You will notice every record has this field ON
Input x For the image x co-ordinate
Input y For the image y co-ordinate
Output x For the output x co-ordinate
Output y For the output y co-ordinate
rms Will display the Root Mean Square for each
record
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