CoastWatch Data Analysis Tool Help: Navigation Analysis
In this section:
About navigation analysis
You can open a navigation analysis panel from the Tools|Navigation Analysis menu. The panel
provides a way to compare the known coastline geography and the
data view image coastline to check for problems with satellite
earth location data. Normally this tool would only be used by
NOAA researchers working with experimental satellite data. The
panel shows a list of navigation points and allows you to add new
points to the list, adjust the navigation offset for each point,
and save the points to a data file.
Analysis panel controls
The panel holds the following components used to add and modify
navigation points:
- Add Point
- Manual and automatic buttons for adding new points to the point
list. Click on one of the buttons, and then click one or more
locations on the main CDAT data view to add each point to the list.
In automatic mode, the navigation point is run through an automatic
navigation algorithm before being added to the list, and the results
of the automatic navigation are shown in the Status column.
- Navigation Points
- The list of navigation points. Clicking on a point shows that
point in the view on the right of the panel. You can delete
selected points from the list, or clear all the points and start
again.
- Navigation Offset
- The navigation offset for the selected point. The Variable and Box size
controls determine what the offset view shows, and also what data is
used for automatic navigation. You can adjust the offset in three
ways: by clicking and dragging the offset view, by manually
adjusting the Row offset and Column offset values, or by clicking the Auto button to perform an automatic navigation.
To reset the offsets back to zero, click Reset. Note that the offset view image is
independent of the main CDAT data view -- it automatically adjusts
the contrast and brightness for the selected navigation point,
variable, and box size.
Saving points
Navigation points from the point list can be saved in either XML or
CSV format. Click Save... and select a set
of points and auxiliary variable data to save with each point. The
XML format writes out each point using XML tags and attributes and is
useful for web browser display and XML readers. The CSV format writes
each point as a line of comma separated values, ready for input to a
spreadsheet or plotting program. In either format, the following data
is saved for each point:
- Earth location - The latitude and longitude of the point.
- Data location - The row and column of the point in the data file.
- North direction - The direction of north for the point as a unit
vector with row and column components.
- Navigation offset - The navigation offset of the point.
- Comment - The status column value indicating either manual or
automatic navigation.
- Variable values - A data value for each variable selected in the save
dialog.
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