2. Marine GIS >
2.4 Graticules & Frames > 2.4.1
2.4.1 Accuracy Check for AOI Frames
New Version of Saga:
Usually a new version of Saga
is quickly assimilated into these exercises. The latest release, Version
2.1.2, is so radically different that it will take some time to catch up with
revised exercises. Please email me immediately whenever you find an old
exercise that simply cannot be accomplished in the new Saga, due to big changes
in the properties, etc. I will try to provide fixes within about 2 days.
|1. This check is
the most important of all, because you use the graticule shape and the lines
shape frame for other checks.
|2. Load the
following shapes into Saga:
- World Borders map (a polygon shape)
- Area of interest graticule (a lines shape)
- Area of interest frame (a lines shape)
- Area of interest frame (a polygon shape)
|3. Use ADD TO MAP to plot the
World Borders data and then plot the graticule on top of it. The
graticule should appear in exactly the place where you want it to be.
|4. Make a map of the
graticule. Enlarge it, and carefully check the X, Y coordinates of
all 4 corners. They must be exactly as expected, but a very
tiny error much smaller than the grid cell size is OK. [This is
due to cursor movement precision.]
NOTE: The coordinates are
displayed along the bottom line of the Saga window.
|5. Plot the lines frame on
top of the graticule (preferably in a different color). They must
|6. Plot the lines frame or
the graticule on top of the polygon frame. They must match exactly.
You absolutely MUST get these accuracy checks right,
because most other checks and data products depend on frames for location,
spatial resolution and size. Don't go forward until you are
sure you have accurate