...
| Administrative levels in boundary polygon shapefile | Required new fields in boundary polyline shapefile |
|---|---|
| Administrative level 0 | AdmLevel (integer) |
| Administrative levels 0 and 1 | LEFT_A0, RIGHT_A0 (text) AdmLevel (integer) |
| Administrative levels 0, 1, and 2 | LEFT_A1, LEFT_A0, RIGHT_A0, RIGHT_A1 (text) AdmLevel (integer) |
| Administrative levels 0, 1, 2, and 3 | LEFT_A2, LEFT_A1, LEFT_A0, RIGHT_A0, RIGHT_A1, RIGHT_A2 (text) AdmLevel (integer) |
- Verify that the AdmLevel values have all been set to zero. Calculate them to zero if they are not.
- Right-click the polyline shapefile > "Joins & Relates" > "Join..." (or properties > Joins & Relates) and provide the Join Data as follows:
- "What do you want to join to this layer?" = Join attributes from a table
- "Choose the field in this layer that the join will be based on:" = LEFT_FID
- "Choose the table to join to this layer, or load the table from disk:" = (the input polygon shapefile)
- "Choose the field in the table to base the join on:" = OBJECTID (or FID)
- Select "Keep only matching records". These will be the line features that are not boarding the sea or a neighboring country.
- (Optionally) Click the ‘Validate Join’ button. Do not expect all records to match - because the ‘left’ side of all exterior lines will have no neighboring polygon. Do not worry if you receive a “Field names that match reserved words should not be used in database schema and can cause the join to fail. The following fields match reserved words….” message
- Click ‘OK’
- Set a definition query to exclude the ‘NULL’ values of the input polygon shapefile. (This might refer to a .FID or a .OBJECTID)
- This should reveal the internal boundary lines. (External boundary lines are deselected because they border the outside of the country and received a 'NULL' left polygon identifyier.)
- Begin editing the polyline shapefile
- Open the output polyline shapefile attribute table
- Use the Field Calculator to calculate all the LEFT_Ax values (for the LEFT_Ax fileds recently added to the polyline shapefile ) equal to the coresponding administrative levels of the polygon shapefile.
...
Check carefully for discontinuities
Calculate Set a definition query for LEFT_A0 = RIGHT_A0 and LEFT_A1 <> RIGHT_A1; calculate AdminLevel = 1.
| Explanation: LEFT_A0 = RIGHT_A0 and LEFT_A1 <> RIGHT_A1 will find the lines that not administrative level 0 borders (either shorelines or international borders) but are separating administrative level 1 units |
|---|
In this map the administrative level 1 polygons are shaded to show that the lines separate administrative level 1 units. |
...