8. Fix a corner or center location.
To configure a projection, you must know the latitude and longitude of either the NE or
SW corner or the center of the display.
Select Fix at the location that you know and then input the LAT/LON coordinates.
With Fix selected, you can change other parameters of the projection geometry
without losing you coordinate information.
9. Specify the projection coverage area (region of the projection) in one of 2 ways:
• Specify the latitude and longitude of one of the 2 unfixed points.
• Specify the distance North (Y-Range) and the distance East (X-Range) from the
center.
The projection menu acts as a spread sheet. When you change a parameter, the other
parameters adjust to reflect the change.
The spreadsheet algorithm converges on a correct solution even for strange
projections. One example where it may not converge is for an AED projection where
the Reference Point is several thousand kilometers from the center of the projection
region.
If you encounter a problem with the spreadsheet, check the reference point and
select Default to load some valid numbers.
10. Specify the pixels.
The number of pixels that are used to represent data in the projection is specified for
the X- and Y-directions of the output display.
If you have specified the other aspects of the projection, input the correct number of X-
pixels (horizontal direction). The number of Y-pixels adjust automatically.
If you adjust the number of Y-pixels, then other parameters of the spread sheet change,
such as the LAT/LON of the unfixed points and the Y-Range.
11. Fine-tune the spread sheet.
Since all of the projection geometry parameters are linked through the spread sheet
algorithm, when you change one parameter, other parameters adjust automatically.
This means that you may need to compromise. The spread sheet makes it easy to
experiment with dierent compromises.
For example, if you want a 480 × 480 pixel Mercator display, both the X- and Y-ranges
cannot in general be made equal (for example, 100 km (62.1 mi)). In this case, the
compromise can be, for example, an X-range of 100 km (62.1 mi) and a Y-range of
99.5 km (61.8 mi) to get a perfect 480 × 480 display.
3.2.3
Product Parameters
In Product Parameters, define the data taken from the task and how to display the data.
Chapter 3 – Configuring IRIS Products
RESTRICTED 23
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