Fix Topological and Geometry Errors using QGIS and Mapshaper
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- Опубликовано: 3 окт 2024
- This video shows how to fix messy vector data and create clean topologically correct datasets.
Data Credit: Kenya Admin4 boundaries, Central Bureau of Statistics(CBS), PCODES developed. Downloaded from data.humdata.o...
The types of errors that we will be fixing are
Sliver Polygons (Gaps)
Overlapping Polygons
Invalid Geometries
Line Intersections
Learn more about Mapshaper spatialthought...
your contribution to geospatial science even to the science community is huge , Thank you Professor for your big effort and sharing valuable techniques from Ethiopia
Thank you for your kind words. 🙏
Lots of Love from Central University of Rajasthan India...the efforts you are making to educate ourselves who are new and working in the field of Environmental Science... Hat's off to you.
Simply love it. very useful tutorial. much appreciated 💚
Wow! This solved my difficulties fixing topology in QGIS. It took less than 10 minutes! Thank you so much!
Thanks for this tutorial very informative
very good explainations, thank you!
really useful, you saved me
Terimakasih kang berkat jasamu pekerjaanku menjadi ringan
thank you and I love You for sharing this.
thank you so much..this helps a lot..
this was amazing, thank you, how does one incorporates this in edge matching, when a map exists between two different data and you do not want that gap and want them to fit at the edge
Thank you! Does the v.clean tool in QGIS do the same thing?
Yes. But v.clean is slower and more clunky to use than mapshaper.
Very useful tip ❤
This is amazing
Sir would kindly make a tutorial on network analysis taking into consideration of the DEM or slope as friction?
See this video where I show how to do it ruclips.net/user/liveZLmdft26seE?si=t6K38xxaZZyQfJOw&t=1544
Step-by-step at github.com/timlinux/QGIS-Freestyle/issues/1#issuecomment-907280453
It seems very powerful and precise, thanks for the useful tutorial!...but.... it doesn't work using more than one shapefile, does it? It would be perfect if it could make a polygonal topological checks between two or more shapefiles/themes/Feature Classes... (i.e. Vegetation+Soils+Urban Areas+polygonal Rivers ....).
Mapshaper can work with multiple layers. You can drag and drop them and use them. See spatialthoughts.com/2019/11/08/optimizing-office-commute/
I am not sure how the topologycal checks would work between 2 layers though.
Legendary ❤
its very useful. can we copy a query of the functions being run in mapshapper and use it in qgis?
No. These are both separate systems and use different algorithms for fixing topology.
@@SpatialThoughts yes i know. But i want the background query to use it in other lamguages like Java or C++.
@@SpatialThoughts i have one more question. I have a data set on global level with some invalid geometries of countries. It is not required to fix the geometries rather to change the projection system and do the topology corrections. How could we resolve the topology issues while using global data of all countries. Should we customize the projection system then take one country as reference point and fix the topolgy of all countries on the basis of it.. Could you guide me in this regard?
Hi! How can it be used to fix topological errors for more than one layer such as overlaps between polygons in different layers ?
Topology can be maintained among features of the same layer only. If your polygons are in different layers, merge them using the 'Merge Vector Layers' tool in QGIS. If the layers represent different themes (like Layer 1 for admin1, Layer 2 for Admin2 etc.) - there's no easy way to harmonize them. It needs to be done manually by editing the polygons.
¿Cómo hacer dicho proceso dentro de QGIS?
I want to fix line error means only fili two line gaps and merge those line how to do ?
Probably best to do it in QGIS by manually editing the layer using the built-in tools. I have an example of how to use hte Vertex Tool to fix a single line gap www.qgistutorials.com/en/docs/3/handling_invalid_geometries.html
sir we are waiting for a webgis course from begginer to advance in qgis
Not a full course but a tutorial on publishing qgis maps on the web using qgiscloud coming soon.
Nice video. Get new ideas from it. I had tried the plugin part but it is more frequent. But Ujjawal Sir, while exporting the layer to shape file it loss the previous attributes that are on original layer. Output layer only contains FID. Any thing on this? Is there any way to retain the attributes.
Mapshaper export preserves all the attributes for me. Did you apply any other operation on the layer? Simply running 'clean' doesn't remove any attributes.
you have to attach all the files not just the .shp
I am unable to export the result as shapefile/kml. Can you please let me know if I may be missing something?
Are you not able to click the 'Export' button in Mapshaper? What error do you get?
@@SpatialThoughtsThere is no error..it is creating a file which is neither a shapefile or kml..It is showing in the folder but it doesn't open in any software...It is also showing size of file as 111kb.
@@amreeshbhullar7925 Send your original file, the steps you applied and the resulting file to me at ujaval@spatialthoughts.com. Will take a look and guide you.
mantab