The relief map polygon coverage

I needed a coverage that would show the Oakwood area in 200m contour bands, so that each polygon would represent the minimum altitude of that area i.e. the 200m polygon would represent the area that was above 200m and below 400m in altitude.To do this I entered ARCEDIT and added the arcs representing the polygons to the base coverage. I also added a label in roughly the middle of each polygon that would hold the height of that polygon. As I entered each label with the digitzer, I made a note of what the height of that polygon was and the ID of the label. I then saved the result in a coverage called contpoly. I also saved it as a coverage called contlines (this will be explained in the next section ).The view in ARCEDIT when I had fished can be seen below in figure 3.

Figure 3 : Relief polygons displayed in ARCEDIT.

Now that I had the arcs of the polygons and their labels digitized, I then had to build the topology, so in ARC I typed.

Arc: build contpoly

Some messages come up which tell me that contpoly.PAT (the polygon attribute table) has been created, this is what I need. The next step was to go into INFO.

Arc: info
 INFO  EXCHANGE  CALL
12/07/1994  10:39:01
 INFO  9.42  11/11/86  52.74.63*
 COPYRIGHT 1986 HENCO SOFTWARE, INC.
 PROPRIETARY TO HENCO SOFTWARE, INC.
 US GOVT AGENCIES SEE USAGE RESTRICTIONS IN HELP FILES (HELP RESTRICTIONS)
 ENTER USER NAME>ARC
 
 ENTER COMMAND > ITEMS    
 ENTER COMMAND >SELECT CONTPOLY.PAT
COLUMN   ITEM NAME        WIDTH OUTPUT  TYPE N.DEC  
  1      AREA               4     12     F      3                        
  5      PERIMETER          4     12     F      3
  9      CONTPOLY#          4      5     B      -
 13      CONTPOLY-ID        4      5     B      -

Having seen the items in the contpoly coverage I created a new file into which I could enter the height data. So in INFO I used the DEFINE command to declare the items that would exist in the new file. Since I would be joining this file to the contpoly.PAT file, one of the items in the new file had to already exist in contpoly.PAT. I had written down the contpoly-id values as I entered the labels so I used this as the common item.

ENTER COMMAND > DEFINE HEIGHTPOL.DAT
ITEM NAME,WIDTH [,OUTPUT WIDTH] ,TYPE [,DECIMAL PLACES] [,PROT.LEVEL]

    1
 ITEM NAME>CONTPOLY-ID,4,5,B
ITEM NAME>

Now that I had a common item I added an item which would hold the height. The usual name for an item which holds heights in ARC-INFO is spot, so I used that. I created a 4 character wide Integer item.

ITEM NAME>SPOT,4,4,I
ITEM NAME>

I then pressed the return key to finish. I entered the polygon id of each polygon and its height using the ADD command.

ENTER COMMAND >SELECT HEIGHTPOL.DAT
0 RECORD(S) SELECTED
ENTER COMMAND > ADD

     1
CONTPOLY-ID> 1
SPOT> 0
     2
CONTPOLY-ID> 2
SPOT> 200
     3
CONTPOLY-ID> 3
SPOT> 400

And on with the rest until all the heights were entered. To finish I pressed the return key and got a message telling me the records had been added. I then entered the Q STOP command to save and leave INFO. Once in ARC I joined the data file to the contpoly.PAT file using the joinitem command. I thus created my polygon relief coverage. Subsequently I created the polygon coverage of the lakes and sea in the same way. To create the contour line vector coverage I had to approach the problem in a different way . We will see how this was handled next.

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