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| How can I create a BLN file? | |||||||||
There are a number of ways to create a BLN file. A BLN file consists of a one line header followed by a list of XY points. The one line header simply is the number of proceeding
data points. If you are using the BLN file for blanking a grid, then the header
will also need to contain a 1 or a 0 (the blanking flag number). A 1 means to
blank inside the boundary and a 0 means to blank outside the boundary. If you
are not using the BLN file for blanking, then it doesn’t matter if you have a 1
or a 0. Some methods to create a BLN file are: 1.
Enter
the Data Manually. The simplest method to create a BLN file is to enter the
coordinates directly into the Surfer worksheet. This works well if you know the
coordinates for the objects you want to describe in the BLN file. If you have 1 data point in your BLN file, then you are
creating a point location. If you have 2 or more data points, then this will be
described as a line. If you have multiple data points, and the first and last
coordinate set are the same, then this is a polygon. For example: A BLN file with two points: 1 <-- point #1 5,6 1 <-- point #2 4,3 A BLN file with
two points and one polyline (made of three points connected together): 1 <-- point #1 5,6 1 <-- point #2 4,3 3 <-- polyline 1,1 4,2 6,5 A BLN file with two points, one polyline, and one
polygon: 1 <-- point #1 5,6 1 <-- point #2 4,3 3 <-- polyline 1,1 4,2 6,5 5 <-- polygon 0,0 5,0 3,4 1,4 0,0 This will look like:
A BLN file with
one polygon that will be used to blank a grid file (outside the boundary): 5,0 <-- BLN header with blanking
flag set to 0 0,0 5,0 3,4 1,4 0,0 You can enter these coordinates in the Surfer worksheet
and then go to File | Save As to save it to a BLN file. If using Notepad or
WordPad, you can simply save to filename.bln. You can load the BLN file into
Surfer as map by going to Map | Base Map (Surfer 8) or Map | New | Base Map
(Surfer 9). 2.
Digitize
the Boundary If you do not know the coordinates for the boundary, but you can visually pick them off a map in Surfer, then you can digitize them. To do this: 1.
Create the map in Surfer 2.
Right click over the map and go to Digitize. Your cursor will turn into a
cross hair. 3.
Click on the first point. The coordinates of
that point will be entered in a text window that appears (called digit.bln). 4.
Digitize all around the boundary in order,
either clockwise or counterclockwise around a polygon or along the length of
the polyline. If you are digitizing multiple objects, separate the ending of
one object and the beginning of the other with an extra blank row between the
coordinates in the digit.bln window. 5.
Once you are done digitizing the data, go to File | Save As in the digit.bln window
and save to a BLN file. 6.
If using the BLN file for blanking a grid file,
open the BLN file in the Surfer worksheet to be sure the BLN flag value is what
you want it to be (cell B1, either a 0 to blank outside the boundary, or a 1 to
blank inside the boundary). 3.
Export
an Existing File You can save an existing vector file
(ie. DXF, SHP, MIF, etc) in the BLN format. To do this: 1. Load
the file as a base map by going to Map |
Base Map (Surfer 8) or Map | New |
Base Map (Surfer 9 and 10). 2. Turn
off the axes in the Object Manager
by unchecking them. 3. Go
to File | Export to export to a BLN
file. If using the BLN file for blanking a
grid file, open the BLN file in the Surfer worksheet to be sure the BLN flag
value in cell B1 is what you want it to be (a 0 to blank outside the boundary,
or a 1 to blank inside the boundary). 4.
Draw
it in the Plot Window If you are using
Surfer 9 or 10, you can simply draw the objects you want over your map and export
them to a BLN file. To do this: 1.
Select your existing map and go to Map | Add | Empty Base Layer. That will
add an empty base map layer, called Base,
to your map. You can see this in the Object
Manager. 2.
Select the new empty base map layer in the Object Manager and go to Arrange | Enter Group. You are now
"inside" the base layer group. 3.
You may want to zoom in a few times so you can
see the map clearly. 4.
Go to Draw
| Polygon and draw your polygon over the map. You can use the scroll bars
on the sides of the window when drawing the polygon. 5.
Double click when you are finished to end the
polygon. Now the base map layer has one polygon object in it. 6.
Press the Esc
key on the keyboard to exit draw mode. 7.
Go to Arrange
| Exit Group to exit the base layer group. 8.
Turn off the four axes in the Object Manager (uncheck them) and any
other map layers (ie. the contour map). 9.
Go to File
| Export. 10. In
the Export dialog, choose a location to save the file, give the file a name,
and choose to save it as BLN Golden
Software Blanking (*.bln). 11. Click Save . 12. In
the Export Options dialog, click Save again and the file is created. If you want to use the BLN file for blanking, and wish to blank outside the polygons, you will need to create a single polygon from the multiple areas in the BLN file. For instructions on how to do this, see: See also: How do I create a BLN file to display multiple polylines? |
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