How To: Create a buffer zone around selected features
You may want to create a new theme which includes only those features that exist within a particular spatial area or that have certain attribute values. These features may be selected with any AutoCAD selection tools or ArcCAD tools (e.g., RESELECT, ASELECT, NSELECT). The entities and features do not have to be visible on the screen for the features to be selected, but entity-feature links must be present.
Once you have selected the desired features, you can use EXTRACT to create a new theme of only the selected features. This new theme will be the input theme for the BUFFER operation, which generates buffer zones around input theme features. The PAT of the output theme will have an additional item called INSIDE. The value for each record will be either 100 (area inside the buffer zone) or 1 (area outside the buffer zone).
The following is an example of creating a buffer around roads:
- Create a feature selection set from an ArcCAD theme.
Theme name (?/<default>): ROADS
Reselect by?(Circle/ENtity/Expression/Polygon/Window): E
Logical expression: ROAD_CODE = 'PRIMARY'
Roads arcs: 7 of 14 selected
- Create a new theme which includes only the selected features.
Input theme (?/<defaults>): ROADS
Output theme (?): PRIMROAD
Theme PRIMROAD is not defined.
GIS data set <PRIMROAD>: <CR>
Symbol number (1-100) <0>: <CR>
Extracting features from roads to create primroad
- Create polygon themes by generating buffer zones around input theme features.
Input theme (?/<default>): PRIMROAD
Output theme (?): ROADBUF
Theme ROADBUF is not defined.
GIS data set (?/<default>):
Shade symbol number (1-100) (?/<0>):
Buffer using? (Item/<Constant>): <cr>
Buffer distance: 200
Fuzzy tolerance <compute>: <cr>