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Touching Polygon Intersection

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0

I have two touching Polygons (two neighbouring counties) and there intersection is a MultiLineString, where:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[0]  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[1] 

gives:

924

LINESTRING (-7.1060859 53.1680546, -7.1061766 53.1678101)

LINESTRING (-7.1061766 53.1678101, -7.1072205 53.1666679)

I would have expected instead:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms)[0])

to give:

1

924

why is intersection giving the result like this? I wish to simplify the borders between a set of bordering counties by reducing the number of points, while at the same time preserving topology.

topology shapely matplotlib

share|improve this question

asked Mar 17 '18 at 20:51

BazBaz

1022

bumped to the homepage by Community♦ 4 mins ago

This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Without knowing your data, this is guesswork.
  
  – inc42
  Aug 4 '18 at 9:11
  

  
  
  
  

add a comment | 

0

I have two touching Polygons (two neighbouring counties) and there intersection is a MultiLineString, where:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[0]  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[1] 

gives:

924

LINESTRING (-7.1060859 53.1680546, -7.1061766 53.1678101)

LINESTRING (-7.1061766 53.1678101, -7.1072205 53.1666679)

I would have expected instead:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms)[0])

to give:

1

924

why is intersection giving the result like this? I wish to simplify the borders between a set of bordering counties by reducing the number of points, while at the same time preserving topology.

topology shapely matplotlib

share|improve this question

asked Mar 17 '18 at 20:51

BazBaz

1022

bumped to the homepage by Community♦ 4 mins ago

This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Without knowing your data, this is guesswork.
  
  – inc42
  Aug 4 '18 at 9:11
  

  
  
  
  

add a comment | 

I have two touching Polygons (two neighbouring counties) and there intersection is a MultiLineString, where:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[0]  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[1] 

gives:

924

LINESTRING (-7.1060859 53.1680546, -7.1061766 53.1678101)

LINESTRING (-7.1061766 53.1678101, -7.1072205 53.1666679)

I would have expected instead:

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms)[0])

to give:

1

924

why is intersection giving the result like this? I wish to simplify the borders between a set of bordering counties by reducing the number of points, while at the same time preserving topology.

topology shapely matplotlib

share|improve this question

asked Mar 17 '18 at 20:51

BazBaz

1022

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[0]  

list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms )[1] 

924

LINESTRING (-7.1060859 53.1680546, -7.1061766 53.1678101)

LINESTRING (-7.1061766 53.1678101, -7.1072205 53.1666679)

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms))

len(list(counties["King's Co."].intersection(counties["Queen's Co."]).geoms)[0])

1

924

share|improve this question

asked Mar 17 '18 at 20:51

BazBaz

1022

share|improve this question

asked Mar 17 '18 at 20:51

BazBaz

1022

asked Mar 17 '18 at 20:51

BazBaz

1022

asked Mar 17 '18 at 20:51

BazBaz

1022

1 Answer
1

active

oldest

votes

0

In your case;

• 
  mls = a.intersection(b) returns MultiLineString.
  
  


• 
  len(mls)gives you lines' count in mls.


• 
  gs = mls.geomsreturns GeometrySequenceand len(gs) equals len(mls).

So, len(mls) = len(mls.geoms) = len(list(mls)) = len(list(mls.geoms)).
More specifically, it's all about __len__() special class method definition.

Note that len(list(mls)) equals len(list(mls.geoms)), however, list(mls)==list(mls.geoms) returns False(but, of course, lines in the lists have similar geometry)

share|improve this answer

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  But why do I get these 2 point LINESTRINGs? I would like a LINESTRING containing all the boarding points, presuming the counties have a single border with each other.
  
  – Baz
  Mar 18 '18 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is probably a small gap between them or the points that you think are overlapping in the two counties' polygon are not actually overlapping.
  
  – Kadir Şahbaz
  Mar 18 '18 at 18:51
  
  
  

  
  
  
  

add a comment | 

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0

In your case;

• 
  mls = a.intersection(b) returns MultiLineString.
  
  


• 
  len(mls)gives you lines' count in mls.


• 
  gs = mls.geomsreturns GeometrySequenceand len(gs) equals len(mls).

So, len(mls) = len(mls.geoms) = len(list(mls)) = len(list(mls.geoms)).
More specifically, it's all about __len__() special class method definition.

Note that len(list(mls)) equals len(list(mls.geoms)), however, list(mls)==list(mls.geoms) returns False(but, of course, lines in the lists have similar geometry)

share|improve this answer

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  But why do I get these 2 point LINESTRINGs? I would like a LINESTRING containing all the boarding points, presuming the counties have a single border with each other.
  
  – Baz
  Mar 18 '18 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is probably a small gap between them or the points that you think are overlapping in the two counties' polygon are not actually overlapping.
  
  – Kadir Şahbaz
  Mar 18 '18 at 18:51
  
  
  

  
  
  
  

add a comment | 

0

In your case;

• 
  mls = a.intersection(b) returns MultiLineString.
  
  


• 
  len(mls)gives you lines' count in mls.


• 
  gs = mls.geomsreturns GeometrySequenceand len(gs) equals len(mls).

So, len(mls) = len(mls.geoms) = len(list(mls)) = len(list(mls.geoms)).
More specifically, it's all about __len__() special class method definition.

Note that len(list(mls)) equals len(list(mls.geoms)), however, list(mls)==list(mls.geoms) returns False(but, of course, lines in the lists have similar geometry)

share|improve this answer

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  But why do I get these 2 point LINESTRINGs? I would like a LINESTRING containing all the boarding points, presuming the counties have a single border with each other.
  
  – Baz
  Mar 18 '18 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is probably a small gap between them or the points that you think are overlapping in the two counties' polygon are not actually overlapping.
  
  – Kadir Şahbaz
  Mar 18 '18 at 18:51
  
  
  

  
  
  
  

add a comment | 

In your case;

• 
  mls = a.intersection(b) returns MultiLineString.
  
  


• 
  len(mls)gives you lines' count in mls.


• 
  gs = mls.geomsreturns GeometrySequenceand len(gs) equals len(mls).

So, len(mls) = len(mls.geoms) = len(list(mls)) = len(list(mls.geoms)).
More specifically, it's all about __len__() special class method definition.

Note that len(list(mls)) equals len(list(mls.geoms)), however, list(mls)==list(mls.geoms) returns False(but, of course, lines in the lists have similar geometry)

share|improve this answer

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

share|improve this answer

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231

answered Mar 18 '18 at 0:33

Kadir ŞahbazKadir Şahbaz

4,48721231