I'm new at this an essentially have very little idea of what I'm doing. (FYI I'm working off of this tutorial: http://bost.ocks.org/mike/map/)
I'm trying to get topojson to work. I've successfully installed homebrew and node. I've done the "npm install -g topojson" part as well.
And then, after that, when I try to type in the "which ogr2ogr" etc -- just, nothing happens. He says if having trouble to edit path variable environments. I have only a vague idea of what that means, and not sure if that's my problem or not.
Let me know what other information you need. I really just want to make a map. The global install does seem to have worked. I just don't know what to do from here.
The tutorial you linked to is a great starting point. I wish I'd seen it before trying to figure everything out on my own. :)
From what I understand, you probably missed the step in which you install gdal. If you're seeing some other errors, please post them in your question.
You can get ogr2ogr working by running:
brew install gdal
Here's some background info for you, so you'll get a better understanding of what's going on there.
topojson and ogr2ogr are two distinct utilities. ogr2ogr is part of the gdal package and in our case is used to generate GeoJSON from a shapefile.
GDAL is a translator library for raster geospatial data formats that is released under an X/MIT style Open Source license by the Open Source Geospatial Foundation. As a library, it presents a single abstract data model to the calling application for all supported formats. It also comes with a variety of useful commandline utilities for data translation and processing.
TopoJSON is used to compress the rather large GeoJSON output from the previous GDAL conversion. It reduces redundancy by specifying paths with arcs rather than discrete points. It's pretty neat, actually:
TopoJSON is an extension of GeoJSON that encodes topology. Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called arcs. TopoJSON eliminates redundancy, offering much more compact representations of geometry than with GeoJSON; typical TopoJSON files are 80% smaller than their GeoJSON equivalents. In addition, TopoJSON facilitates applications that use topology, such as topology-preserving shape simplification, automatic map coloring, and cartograms.
The output of these two steps (shapefile -> GeoJSON -> TopoJSON) will be a JSON string which is easily interpreted by JavaScript. You'll need to use topojson in your drawing code to convert back to GeoJSON for actually drawing the map.
Recall from earlier the two closely-related JSON geographic data formats: GeoJSON and TopoJSON. While our data can be stored more efficiently in TopoJSON, we must convert back to GeoJSON for display. Breaking this step out to make it explicit:
var subunits = topojson.object(uk, uk.objects.subunits);
For ubuntu, I used this way to have ogr2ogr
sudo apt-get install gdal-bin
来源：https://stackoverflow.com/questions/14173853/troubleshooting-topojson-installation