QGIS3 - Join by location (falsely) adds neighbouring polygons
I have two layers:
Layer 1 - containing municipalities of country X in the year 2014 (around 600)
Layer 2 - containing municipalities of country X in the year 2018 (around 500)
Between 2014-2018 several municipalities have merged. E.g. municipality A, B and C in the 2014 layer no longer exist in 2018 but are now part of municipality D.
I want to know for each 2014 municipality what its corresponding 2018 municipality is. So for municipality A, B and C the outcome should be D.
I tried to achieve this by performing Join by Location (using intersect). I would expect the joined layer to have 600 features (i.e. the number of 2014 municipalities) with a new attribute containing the corresponding 2018 municipality. However, the joined layer I get has over 2400 features. Municipality A is present 4 times, one entry has municipality D as new attribute (as expected) but the other 3 entries have the neighbouring municipalities of A as new attribute (E, F and I). I.e. QGIS seems to think that municipality A does not only intersect with D but also with all neighbouring municipalities of A.
Am I doing something wrong here?
Both layers have the same CRS.
qgis
asked 1 hour ago
tilkastilkas
112
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I have two layers:
Layer 1 - containing municipalities of country X in the year 2014 (around 600)
Layer 2 - containing municipalities of country X in the year 2018 (around 500)
Between 2014-2018 several municipalities have merged. E.g. municipality A, B and C in the 2014 layer no longer exist in 2018 but are now part of municipality D.
I want to know for each 2014 municipality what its corresponding 2018 municipality is. So for municipality A, B and C the outcome should be D.
I tried to achieve this by performing Join by Location (using intersect). I would expect the joined layer to have 600 features (i.e. the number of 2014 municipalities) with a new attribute containing the corresponding 2018 municipality. However, the joined layer I get has over 2400 features. Municipality A is present 4 times, one entry has municipality D as new attribute (as expected) but the other 3 entries have the neighbouring municipalities of A as new attribute (E, F and I). I.e. QGIS seems to think that municipality A does not only intersect with D but also with all neighbouring municipalities of A.
Am I doing something wrong here?
Both layers have the same CRS.
qgis
asked 1 hour ago
tilkastilkas
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I have two layers:
Layer 1 - containing municipalities of country X in the year 2014 (around 600)
Layer 2 - containing municipalities of country X in the year 2018 (around 500)
Between 2014-2018 several municipalities have merged. E.g. municipality A, B and C in the 2014 layer no longer exist in 2018 but are now part of municipality D.
I want to know for each 2014 municipality what its corresponding 2018 municipality is. So for municipality A, B and C the outcome should be D.
I tried to achieve this by performing Join by Location (using intersect). I would expect the joined layer to have 600 features (i.e. the number of 2014 municipalities) with a new attribute containing the corresponding 2018 municipality. However, the joined layer I get has over 2400 features. Municipality A is present 4 times, one entry has municipality D as new attribute (as expected) but the other 3 entries have the neighbouring municipalities of A as new attribute (E, F and I). I.e. QGIS seems to think that municipality A does not only intersect with D but also with all neighbouring municipalities of A.
Am I doing something wrong here?
Both layers have the same CRS.
qgis
asked 1 hour ago
tilkastilkas
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I have two layers:
Layer 1 - containing municipalities of country X in the year 2014 (around 600)
Layer 2 - containing municipalities of country X in the year 2018 (around 500)
Between 2014-2018 several municipalities have merged. E.g. municipality A, B and C in the 2014 layer no longer exist in 2018 but are now part of municipality D.
I want to know for each 2014 municipality what its corresponding 2018 municipality is. So for municipality A, B and C the outcome should be D.
I tried to achieve this by performing Join by Location (using intersect). I would expect the joined layer to have 600 features (i.e. the number of 2014 municipalities) with a new attribute containing the corresponding 2018 municipality. However, the joined layer I get has over 2400 features. Municipality A is present 4 times, one entry has municipality D as new attribute (as expected) but the other 3 entries have the neighbouring municipalities of A as new attribute (E, F and I). I.e. QGIS seems to think that municipality A does not only intersect with D but also with all neighbouring municipalities of A.
Am I doing something wrong here?
Both layers have the same CRS.
qgis
qgis
asked 1 hour ago
tilkastilkas
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
tilkastilkas
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
tilkas
asked 1 hour ago
tilkastilkas
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 1 hour ago
tilkastilkas
112
asked 1 hour ago
tilkastilkas
112
112
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
tilkas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
The solution is to do the following:
- Generate the centroids of the polygons of 2014
- Spatially join the centroids with the polygons of 2018
- Join by attribute the polygons of 2014 with their centroids
I hope this would help.
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
add a comment |
Set it up the following:
- As
input layerchoose your old municipalities (2014). - As
join layerchoose your new municiplaities (2018). - As
geometric predicatechoose overlaps, within and equals.
The result:
Of course this will only work if the actual boundaries did not move.
answered 45 mins ago
MrXsquaredMrXsquared
962216
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The solution is to do the following:
- Generate the centroids of the polygons of 2014
- Spatially join the centroids with the polygons of 2018
- Join by attribute the polygons of 2014 with their centroids
I hope this would help.
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
add a comment |
The solution is to do the following:
- Generate the centroids of the polygons of 2014
- Spatially join the centroids with the polygons of 2018
- Join by attribute the polygons of 2014 with their centroids
I hope this would help.
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
add a comment |
The solution is to do the following:
- Generate the centroids of the polygons of 2014
- Spatially join the centroids with the polygons of 2018
- Join by attribute the polygons of 2014 with their centroids
I hope this would help.
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
The solution is to do the following:
- Generate the centroids of the polygons of 2014
- Spatially join the centroids with the polygons of 2018
- Join by attribute the polygons of 2014 with their centroids
I hope this would help.
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
answered 1 hour ago
Mohannad AdhamMohannad Adham
31915
31915
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
add a comment |
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
1
1
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
To add to this Intersection includes where the boundaries of a pair of polygons overlap (what you think of as touching).
– Ian Turton♦
1 hour ago
add a comment |
Set it up the following:
- As
input layerchoose your old municipalities (2014). - As
join layerchoose your new municiplaities (2018). - As
geometric predicatechoose overlaps, within and equals.
The result:
Of course this will only work if the actual boundaries did not move.
answered 45 mins ago
MrXsquaredMrXsquared
962216
add a comment |
Set it up the following:
- As
input layerchoose your old municipalities (2014). - As
join layerchoose your new municiplaities (2018). - As
geometric predicatechoose overlaps, within and equals.
The result:
Of course this will only work if the actual boundaries did not move.
answered 45 mins ago
MrXsquaredMrXsquared
962216
add a comment |
Set it up the following:
- As
input layerchoose your old municipalities (2014). - As
join layerchoose your new municiplaities (2018). - As
geometric predicatechoose overlaps, within and equals.
The result:
Of course this will only work if the actual boundaries did not move.
answered 45 mins ago
MrXsquaredMrXsquared
962216
Set it up the following:
- As
input layerchoose your old municipalities (2014). - As
join layerchoose your new municiplaities (2018). - As
geometric predicatechoose overlaps, within and equals.
The result:
Of course this will only work if the actual boundaries did not move.
answered 45 mins ago
MrXsquaredMrXsquared
962216
answered 45 mins ago
MrXsquaredMrXsquared
962216
answered 45 mins ago
MrXsquaredMrXsquared
962216
answered 45 mins ago
MrXsquaredMrXsquared
962216
962216
add a comment |
add a comment |
tilkas is a new contributor. Be nice, and check out our Code of Conduct.
tilkas is a new contributor. Be nice, and check out our Code of Conduct.
tilkas is a new contributor. Be nice, and check out our Code of Conduct.
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