Geography Reference
In-Depth Information
Use tabs to separate the values! The first line of your file will look something like this:
1 0.21 2.28 1573792.8 176684.5
except, of course, you would use the numbers you found when digitizing instead of 0.21
and 2.28.
27.
Make this four-line file with a text editor, calling it Foozit_Parklot.txt and save it in
___IGIS-Arc_
YourInitials
\Digitize&Transform
28.
Back in ArcMap, zoom to the full extent of both datasets. You may (or may not) see a tiny red
dot on the left of the map window at around (0,0), which is School_Court_A, and a little black
smudge at the right at around (1575000,180000), which is six.tif. (To see the coordinates,
look at the status bar at the bottom right of the window.) Start editing School_Court_A from
the Editor toolbar. Turn on the Spatial Adjustment toolbar, under More Editing Tools in the Editor
toolbar drop-down menu.
29.
In the Spatial Adjustment toolbar drop-down menu, mouse over Set Adjust Data and read
its ToolTip. Click. Click the radio button to pick All features in these layers. Make sure
School_Court_A is checked as the data to adjust (i.e., transform). Click OK. Again, in the
drop-down menu, make sure that Adjustment Methods > Transformation - Affine is checked
for the adjustment method. Under Links pick Open Links File, specifying Foozit_Parklot.txt in
Digitize&Transform (looking at All Files). Click Open.
If you have done everything right, you will now note lines running from the tiny red dot (the digitized school
court) in an east-northeast direction toward the black smudge (the School_Court_A orthophotoquad).
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30.
Zoom in on the digitized court. You should see lines running from each corner, in accordance
with the text file table you made. See Figure 5-7.
31.
For the following operations refer to Figures 5-8 and 5-9 as necessary; but mostly pay attention
to what is happening on the computer monitor. Zoom back to the bookmark School. Here you
will see the easternmost ends of these “transformation lines.” Zoom in on the parking lot
where the Foozit Court is to be placed. From the arrowheads note where the corners of the
Foozit Court will be. From Spatial Adjustment > Links > View Link Table, make the Link Table
appear. One at a time, click the ID value in the link table and note the flashing link to the
parking lot.
You can also see, as the last column in the link table, the residual error for each link, which is the number
of feet by which the corners of the court don't exactly fit the digitized image. It should be 0.05 or less.
That is, the rectangle specified by the corners of the digitized feature cannot be stretched
linearly
to
exactly fit the surveyor's corners, but the small numbers tell you that the transformation is going to go
very well. If these numbers are large, or if the arrowheads don't appear to look right, something has gone
wrong. If there is a problem, select Delete Links and go back and fix things—which probably means you
need to revise the text file.
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The lines may appear to be running in the wrong direction or may not appear at all, due to a bug in the program.
If they do, just keep zooming in. My experience is that at a zoom level of 1:9 (a “9” typed into the text box on the
Standard toolbar) will produce the correct image.
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