How can GeoJSON data to TopoJSON be converted?
TopoJSON files are often smaller than GeoJSON and the conversion allows you to incrementally simplify a dataset, if you wish.
4 Answers
Glad you asked, oh handsome OP.
Install topojson
From the command line (Mac OSX 10.8, assumes homebrew installed):
brew install node.js
npm install -g topojson
Convert The Data
topojson -o output.json input.json
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1
The function to create a topojson from a geojson in topojson has been moved to geo2topo
npm install topojson-server -g
geo2topo input.geojson > output.topojson
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For me this does not work. I am getting a
not recognizederror when trying to rungeo2topoafter runningnpm install topojson-server– JoeBeJan 31, 2020 at 2:34 -
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thanks. This worked perfectly. It would be great if you could tell me what the difference is here? Why do I need a global flag for this whereas for other libraries I installed until now this was not necessary? What happens behind the hood?– JoeBeFeb 10, 2020 at 1:51
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1Install globally if you are using a package as a command line tool and locally if it only needs to be accessible from scripts in an app stackoverflow.com/a/8951576/441878– ow3nFeb 10, 2020 at 11:25
I ported the TopoJSON code from JavaScript to Python, following the exact same format Mike uses in his library (along with his +300 tests).
If you feel better with Python, just install the library by running:
pip install pytopojson
And then run:
python geo2topo.py geojson_file
You can also use a quantization parameter. Just use the -h argument to see how it works.
Let me know if this was helpful to you!
I have found pretty good online tool for simplifying geospatial data (including GeoJSON) and export to various formats (including TopoJSON) at https://geoprocessing.online/tool/simplify-polygons/. You can upload the GeoJSON, set simplification level and export to TopoJSON. For more information on data size reduction, see this article: https://kb.geoczech.org/knowledge-base/how-to-reduce-size-of-vector-data/
topojson -o output_file.json input_file.jsonworks for me under 1.1.0 and 1.4.0. Perhaps you can ask a formal question on here with more info on the problem you're having? Cheers!