Drawing a simple map in Autocad using BPOLY

 



DRAWING A MAP FROM THE DATA IN THE `FLYOURINITIALS' DATABASE




        Problem: using the data from the `flyourintials' dataset, draw a GRANITE 
body and two DIABASE dikes cutting a sucession composed of SANDSTONE and 
LIMESTONE.

        Procedure:

        1) Load Fieldlog and PLOT the STATYPE, STATNUM, LITHCODE, and 
METALS fields in your `flyourinitials' Fieldlog database. Logoff and unload Fieldlog.

        2) In the SETTINGS menu click on LAYER CONTROL to retrieve the 
Layers menu. Type the name `1GRANITE' in the box beneath the NEW button, and 
click the NEW button. This will create a layer named `1GRANITE'. Click the set 
colour button and click on the standard red button to set the 1GRANITE layer to the 
colour red. Similarly, create a layer for 1DIABASE (blue), 1SANDSTONE (yellow), 
1LIMESTONE (CYAN), and a bounding RECTANGLE (MAGENTA). Make the 
RECTANGLE layer current and exit the LAYERS menu.

        Since it would be more convenient to draw a rectangle around the data with the 
latter occupying less space than the whole screen (`zoom' `extents'), type `z' (zoom) 
ENTER and `d' (dynamic) ENTER to carry out a dynamic zoom operation; click the 
left button on the puck (mouse), drag the zoom window to a size greater than that 
occupied by the data, click the left button again, and press ENTER. The data will be 
sized to a lower resolution than EXTENTS. Select RECTANGLE in the DRAW menu 
and draw a rectangle of appropriate size around the plotted data set on the 
RECTANGLE layer.

        Should the rectangle base point be greater than 10000, MOVE the rectangle to 
base point 0,0, (otherwise BPOLY won't work!).

        Return to the LAYERS menu and make the `1GRANITE' layer current. 
(Click ENTITY MODES in the SETTINGS menu to define the characteristics (Colour 
`red'; elevation (= topology) `1') of the line you are about to draw as the boundary of 
the granite unit. Draw or sketch a 'granite' as a closed polygon delimiting the oucrops of 
granite. The granite boundary should appear as an irregular polygon. Return to the 
LAYERS menu, and make the DIABASE layer current. In ENTITY MODES set the 
elevation value to `2'.

        Exit the LAYERS menu, draw two separate diabase boundary lines beginning 
and ending a small distance beyond the rectangle boundary and crossing the 
GRANITE. There should now be four entities in the drawing, one GRANITE polygon, 
two DIABASE polylines, and the rectangle boundary. Type `BPOLY' `ENTER', and 
PICK POINT in the BPOLY menu. Click inside the two polygons bounded by the 
relevant parts of the granite polygon, the boundary rectangle, and the two diabase 
polylines. A closed polyline bounded by the granite, the rectangle and the diabase 
boundary lines will be created. Type `e' (ERASE) `ENTER' and click the parts of the 
diabase polylines inside the granite polygon, or those parts of the diabase polygon 
beyond the rectangle boundary. This will remove the original diabase boundary lines. 
IMPORTANT: use MODIFY CHANGE POINTS etc, to change the elevation 
value of the Bpoly polygons to `2'.

Make the SANDSTONE layer current and draw a single line representing a
boundary separating the sandstone and limestone on both sides of the granite. Extend
the lines beyond the rectangle boundary. Use BPOLY to create two sandstone polygons
bounded by the granite, the diabase, the rectangle, and the sandstone-limestone
boundary. Use MODIFY CHANGE to give the sandstone polyline objects a Z value of
`3'. Repeat the BPOLY procedure for the limestone and use MODIFY CHANGE to
give the limestone polygons a Z value of `4'. Erase the sandstone-limestone boundary by
clicking on its extension either in the granite or beyond the rectangle.
Save the file in the `flyourinitials' directory as `flyourinitials.dwg'.
To form a .DXF file, see the file `acadtoid.rtf'.

PLOTTING THE MAP

Type PLOT 'ENTER' to load the plot menu.
Click the 'File Name' box to enter a file name.
Check the 'Plot to File' and 'Display' buttons.
Click the 'Full' button in the 'Preview' box and double click 'Preview' to see the
output dimensions.
If the dimensions are not satisfactory, change the scaling factors in the 'Plotted
inches = Drawing units' box.
Click OK to output the PLT file.
To send the PLT file to the printer, exit Autocad and execute the batch file
cadtolex.bat at the DOS command line as 'cadtolex c:\directory\filename.plt', e.g.
'cadtolex c:\sh\shuwomap.plt'.
If plotting from a computer with Windows95, exit Autocad, re-enter
Windows95 from DOS, re-enter DOS by clicking the DOS icon, and enter 'copy /b
c:\directory\filename.plt \spool\optra_ra'.

EXPORTING A DXF FILE THAT CAN BE READ BY CORELDRAW OR IDRISI

To convert a DXF file created in Autocad and containing symbols drawn by
Fieldlog, the Dxf file must be converted to Autocad version 10 using the following bat
file 12to10.bat, which uses the acad conversion program dxfix.exe:
rem %1 = input file name; %2 = output file name
rem type 12to10 input_file_name output_file_name
cd c:\acad\support
dxfix -a6 %1 %2
cd c:\

FIGURES

Figure 1. Plate Tectonics.

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