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The Map | Base Map method does not have the ability
to fill outside a polygon, but there are other methods to consider:
- To mask (or blank) contours outside a boundary in a BLN file, use the Grid | Blank command to blank the grid
nodes that are outside the polygon. Set the header flag in the BLN file to 0
to blank outside. Create a new map with the new GRD file.
-or-
- Create a complex polygon covering the area outside the polygon. In other words, you can modify the BLN file to add a
frame around the internal polygon. For example, if you want to
fill the area outside a square that extends from (1,1) to
(2,2), and the map ranges from (0,0) to (9,7), then the [.BLN]
format is as follows:
|
Example of
modified file with frame around the internal polygon. |
Modified file in BLN format
11, 1
|
|
"Total number of values, blanking flag 1 (blank inside)
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| 0.0, 0.0 |
|
"x1, y1. This is the extents of the outer polygon (the map extents)
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| 9.0, 0.0 |
|
|
| 9.0, 7.0 |
|
|
| 0.0, 7.0 |
|
|
| 0.0, 0.0 |
|
"Repeat x1, y1 to close
outer polygon |
| 1.0, 1.0 |
|
"Start internal polygon (the small square in the middle)
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| 2.0, 1.0 |
|
|
| 2.0, 2.0 |
|
|
| 1.0, 2.0 |
|
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| 1.0, 1.0 |
|
"Close internal polygon |
| 0.0, 0.0 |
|
"Repeat x1, y1 to close
outer polygon |
The BLN format draws the connecting line from the internal polygon to
the repeated (x1, y1) point at (0,0). Set the line style to Invisible for
this base map, or use the BNA format, which does not draw the connecting
line:"Start internal polygon.format draws the connecting line from the internal polygon to
the repeated (x1,y1) point at (0,0). Set the line style to Invisible for
this base map, or use the BNA format, which does not draw the connecting
line:
Modified file in BNA format
"","",11
0.0 0.0
9.0 0.0
9.0 7.0
0.0 7.0
0.0 0.0
1.0 1.0
2.0 1.0
2.0 2.0
1.0 2.0
1.0 1.0
0.0 0.0
|
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