Invalid multipolygon of valid individual polygons

up vote
1
down vote

favorite

Could anyone please explain this to me? The polygons all have valid geometry but the resulting multipolygon somehow doesn't. The following script:

from shapely.geometry import Polygon, MultiPolygon

polygon1 = Polygon([(0,0), (1,0), (1,1), (0,1), (0,0)])
polygon2 = Polygon([(1,1), (2,1), (2,2), (1,2), (1,1)])
polygon3 = Polygon([(1,0), (2,0), (2,1), (1,1), (1,0)])
polygon_list = [polygon1,polygon2, polygon3]

mpolygon = MultiPolygon(polygon_list)

for item in polygon_list:
 print(item.is_valid)
for item in mpolygon:
 print(item.is_valid)

print(mpolygon.is_valid)

returns the following:

True
True
True
True
True
True
False

I believe this is causing me problems as I need to intersect a multilinestring with a multipolygon, and the intersection method requires for all the polygon geometries to be valid.

Why are the individual polygons valid while the full multipolygon is not?

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

add a commentÂ |Â

up vote
1
down vote

favorite

Could anyone please explain this to me? The polygons all have valid geometry but the resulting multipolygon somehow doesn't. The following script:

from shapely.geometry import Polygon, MultiPolygon

polygon1 = Polygon([(0,0), (1,0), (1,1), (0,1), (0,0)])
polygon2 = Polygon([(1,1), (2,1), (2,2), (1,2), (1,1)])
polygon3 = Polygon([(1,0), (2,0), (2,1), (1,1), (1,0)])
polygon_list = [polygon1,polygon2, polygon3]

mpolygon = MultiPolygon(polygon_list)

for item in polygon_list:
 print(item.is_valid)
for item in mpolygon:
 print(item.is_valid)

print(mpolygon.is_valid)

returns the following:

True
True
True
True
True
True
False

I believe this is causing me problems as I need to intersect a multilinestring with a multipolygon, and the intersection method requires for all the polygon geometries to be valid.

Why are the individual polygons valid while the full multipolygon is not?

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

add a commentÂ |Â

up vote
1
down vote

favorite

Could anyone please explain this to me? The polygons all have valid geometry but the resulting multipolygon somehow doesn't. The following script:

from shapely.geometry import Polygon, MultiPolygon

polygon1 = Polygon([(0,0), (1,0), (1,1), (0,1), (0,0)])
polygon2 = Polygon([(1,1), (2,1), (2,2), (1,2), (1,1)])
polygon3 = Polygon([(1,0), (2,0), (2,1), (1,1), (1,0)])
polygon_list = [polygon1,polygon2, polygon3]

mpolygon = MultiPolygon(polygon_list)

for item in polygon_list:
 print(item.is_valid)
for item in mpolygon:
 print(item.is_valid)

print(mpolygon.is_valid)

returns the following:

True
True
True
True
True
True
False

I believe this is causing me problems as I need to intersect a multilinestring with a multipolygon, and the intersection method requires for all the polygon geometries to be valid.

Why are the individual polygons valid while the full multipolygon is not?

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

Could anyone please explain this to me? The polygons all have valid geometry but the resulting multipolygon somehow doesn't. The following script:

from shapely.geometry import Polygon, MultiPolygon

polygon1 = Polygon([(0,0), (1,0), (1,1), (0,1), (0,0)])
polygon2 = Polygon([(1,1), (2,1), (2,2), (1,2), (1,1)])
polygon3 = Polygon([(1,0), (2,0), (2,1), (1,1), (1,0)])
polygon_list = [polygon1,polygon2, polygon3]

mpolygon = MultiPolygon(polygon_list)

for item in polygon_list:
 print(item.is_valid)
for item in mpolygon:
 print(item.is_valid)

print(mpolygon.is_valid)

returns the following:

True
True
True
True
True
True
False

I believe this is causing me problems as I need to intersect a multilinestring with a multipolygon, and the intersection method requires for all the polygon geometries to be valid.

Why are the individual polygons valid while the full multipolygon is not?

python shapely

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

edited 43 mins ago

Kadir

3,88011226

edited 43 mins ago

Kadir

3,88011226

edited 43 mins ago

Kadir

3,88011226

asked 1 hour ago

user32882

99911124

asked 1 hour ago

user32882

99911124

asked 1 hour ago

user32882

99911124

add a commentÂ |Â

2 Answers
2

active

oldest

votes

up vote
2
down vote

accepted

It's because polygon1 and polygon3 that you created intersect along an infinite amount of points. Taken here from the Shapely documentation:

enter image description here
...On the right, a valid MultiPolygon with 2 members, and on the right, a MultiPolygon that is invalid because its members touch at an infinite number of points (along a line). Link

To fix this, you need to shift polygon3 so that it will have a maximum of one intersecting point with the other polygons (or none at all).

Your polygons plotted:

enter image description here

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

add a commentÂ |Â

up vote
1
down vote

In addition to @15Step's answer, If you want to fix the invalidity, use buffer method. But if polygons are adjacent, you get polygon instead of multipolygon.

mpolygon = mpolygon.buffer(0)
print(mpolygon.is_valid)
print(type(mpolygon))
# OUT:
# True
# <class 'shapely.geometry.polygon.Polygon'>

enter image description here

If you need multipolygon, you have to convert polygon to multipolygon.

if isinstance(mpolygon, Polygon):
 mpolygon = Multipolygon([mpolygon.buffer(0)])

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

add a commentÂ |Â

Your Answer

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "79"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
convertImagesToLinks: false,
noModals: false,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);

);

draft saved

draft discarded

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fgis.stackexchange.com%2fquestions%2f298307%2finvalid-multipolygon-of-valid-individual-polygons%23new-answer', 'question_page');

);

Post as a guest

Name

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
2
down vote

accepted

It's because polygon1 and polygon3 that you created intersect along an infinite amount of points. Taken here from the Shapely documentation:

To fix this, you need to shift polygon3 so that it will have a maximum of one intersecting point with the other polygons (or none at all).

Your polygons plotted:

enter image description here

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

add a commentÂ |Â

up vote
2
down vote

accepted

It's because polygon1 and polygon3 that you created intersect along an infinite amount of points. Taken here from the Shapely documentation:

To fix this, you need to shift polygon3 so that it will have a maximum of one intersecting point with the other polygons (or none at all).

Your polygons plotted:

enter image description here

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

add a commentÂ |Â

up vote
2
down vote

accepted

It's because polygon1 and polygon3 that you created intersect along an infinite amount of points. Taken here from the Shapely documentation:

To fix this, you need to shift polygon3 so that it will have a maximum of one intersecting point with the other polygons (or none at all).

Your polygons plotted:

enter image description here

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

It's because polygon1 and polygon3 that you created intersect along an infinite amount of points. Taken here from the Shapely documentation:

To fix this, you need to shift polygon3 so that it will have a maximum of one intersecting point with the other polygons (or none at all).

Your polygons plotted:

enter image description here

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

edited 38 mins ago

answered 44 mins ago

15Step

1,1911217

answered 44 mins ago

15Step

1,1911217

answered 44 mins ago

15Step

1,1911217

add a commentÂ |Â

up vote
1
down vote

In addition to @15Step's answer, If you want to fix the invalidity, use buffer method. But if polygons are adjacent, you get polygon instead of multipolygon.

mpolygon = mpolygon.buffer(0)
print(mpolygon.is_valid)
print(type(mpolygon))
# OUT:
# True
# <class 'shapely.geometry.polygon.Polygon'>

enter image description here

If you need multipolygon, you have to convert polygon to multipolygon.

if isinstance(mpolygon, Polygon):
 mpolygon = Multipolygon([mpolygon.buffer(0)])

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

add a commentÂ |Â

up vote
1
down vote

In addition to @15Step's answer, If you want to fix the invalidity, use buffer method. But if polygons are adjacent, you get polygon instead of multipolygon.

mpolygon = mpolygon.buffer(0)
print(mpolygon.is_valid)
print(type(mpolygon))
# OUT:
# True
# <class 'shapely.geometry.polygon.Polygon'>

enter image description here

If you need multipolygon, you have to convert polygon to multipolygon.

if isinstance(mpolygon, Polygon):
 mpolygon = Multipolygon([mpolygon.buffer(0)])

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

add a commentÂ |Â

up vote
1
down vote

In addition to @15Step's answer, If you want to fix the invalidity, use buffer method. But if polygons are adjacent, you get polygon instead of multipolygon.

mpolygon = mpolygon.buffer(0)
print(mpolygon.is_valid)
print(type(mpolygon))
# OUT:
# True
# <class 'shapely.geometry.polygon.Polygon'>

enter image description here

If you need multipolygon, you have to convert polygon to multipolygon.

if isinstance(mpolygon, Polygon):
 mpolygon = Multipolygon([mpolygon.buffer(0)])

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

In addition to @15Step's answer, If you want to fix the invalidity, use buffer method. But if polygons are adjacent, you get polygon instead of multipolygon.

mpolygon = mpolygon.buffer(0)
print(mpolygon.is_valid)
print(type(mpolygon))
# OUT:
# True
# <class 'shapely.geometry.polygon.Polygon'>

enter image description here

If you need multipolygon, you have to convert polygon to multipolygon.

if isinstance(mpolygon, Polygon):
 mpolygon = Multipolygon([mpolygon.buffer(0)])

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

edited 3 mins ago

answered 15 mins ago

Kadir

3,88011226

answered 15 mins ago

Kadir

3,88011226

answered 15 mins ago

Kadir

3,88011226

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

add a commentÂ |Â

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

I need an mpolygon, because I wish to do mpolygon.intersection(multilinestring) where mpolygon has many polygons and multilinestring has many LineStrings which may or may not share vertices
â€“Â user32882
8 mins ago

add a commentÂ |Â

draft saved

draft discarded

draft saved

draft discarded

Post as a guest

Name

Search This Blog

Iyfjky