Hi Rich,
I guess there is 2 parts in this job:
1. Splitting the regions/polylines into segments
2. Finding the segments that not are shared by two regions
As for the first I guess there are some tools out there, maybe
DirectionsMag, that can do this for you, but my guess is that you'll end up
with splitting your regions/polylines into simple lines.
As for the later which actual is where the fun starts, I guess you will be
able to do some magic with buffers.
1. Create a column to hold unique ID's (eg. ID)for each object and update
this column with the value of ROWID
2. Make a copy of your table with the lines
3. Replace the objects in this copy table with a buffer of let's say 0.1 m
in radius.
Using the MapBasic window:
Update LINES_COPY Set OBJ =
Buffer(CreatePoint(CentroidX(OBJ), CentroidY(OBJ)), 12, 0.1, "m")
4. Save this table
5. Now add a column to hold the number of lines intersecting this buffer
6. Update this column using Table > Update column:
Update Table LINES_COPY
Column NUM_LINES
With value from table LINES
Where object from COPY_LINES Intersects objects from LINES
Calculate COUNT
7. Now the column NUM_LINES holds the number of lines intersecting this
buffer, so now we only need to find the lines which matching buffer only
intersects a single line:
Select *
From LINES
Where ID In (Select ID From LINES_COPY Where NUM_LINES = 1)
But beware this SQL select cvan be somewhat slow depending on the number of
objects in your table. It might be faster to select all lines where
NUM_LINES > 1 and then use the Invert Selection to select the other.
8. Now you have selected all those lines that aren't shared.
Et voila,
Peter Horsb�ll M�ller
GIS Developer
Geographical Information & IT
COWI A/S
Rug�rdsvej 55
DK-5000 Odense
Denmark
Tel +45 6313 5013
Direct +45 6313 5008
Mob +45 5156 1045
Fax +45 6313 5090
E-mail [EMAIL PROTECTED]
http://www.cowi.dk
COWI GIS konference afvikles i dagene d. 2.-3. september.
Se yderligere oplysninger p� www.cowi.dk/Div04/Profiles/nyheder.asp
> -----Original Message-----
> From: Rick Luangkhot [mailto:[EMAIL PROTECTED]
> Sent: Thursday, July 03, 2003 5:41 PM
> To: [EMAIL PROTECTED]
> Subject: MI-L Keeping the inside lines of a region/pline
>
>
>
>
>
>
> Hello Listers,
>
> I had a question I was hoping someone can help me out with.
> I have regions that are sharing common boundaries. I want to
> convert them to plines and keep the common boundaries but
> delete the boundaries that are not shared. For example I have
> a wheel with spokes. I want to keep the spokes but not the
> outer wheel circle. Is there any tool or some other way to do this?
>
> Any help in this matter is appreciated.
>
> Thank you much,
>
> Rick
>
>
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