I am new to Open Street Map. For my project, I have to deal with NYC road network, so only streets and their intersections.
The problem is that, in the OSM files I have downloaded, not all intersections are present: if I take a look at the map on the website, I can see that, per each way, all intersections it traverses are referenced, but when I visualize the imports in QGIS, they are not there.
Is there anything that I am doing wrong or not considering?
I’m not familiar with QGIS, but I suspect that you’ll need to go into more detail about how you got the OSM data and how you imported into QGIS before anyone can comment as to why some things are missing.
You’ll also probably need to explain what you mean by “intersection” - what are you expecting to be in the OSM XML data that you obtained that says “there is an intersection here”?
In addition to what SomeoneElse has requested, you should also provide an explicit example on the OSM map in sufficient detail that people can find it and check what is actually on the OSM map. At the very least, the URL for a fully zoomed in view of the problem area, but, ideally you should include the node and way IDs of some of the key features in dispute.
Sorry about that, I am going to be more precise!
I tried different imports. First of all, I used the OSM plugin embedded in QGIS to download OSM data (both setting manually the bounding box of the area I am interested in and getting a “snapshot” with map canvas), then I import the downloaded OSM files in QGIS and finally I export them to Shapefiles (I take “highway” and “oneway” tags for a “way”, no tags for a “node”). I also tried to download the OSM file or even the shapefile of NYC from Metro Extracts, but the result is the same.
Here are the pictures:
On Open Street Map:
In this example, the issue is with “Manila Avenue” (way id = 416489183 or go to http://www.openstreetmap.org/way/416489183).
By “intersection” I mean that, when two roads have a node in common (so no underpass or whatever), then that node should be present.
As you can see, my map does not show any of the “intersections”, so take node “103880177” as an example (intersection between Manila Avenue and 6th Street).
What I found out is that node “103880177” is present in the nodes reference list of Manila Avenue, but not in the nodes shapefile generated.
If you need me to be more specific, please let me know!
I agree with you, in fact I have just used PostgreSQL with PostGIS + Osmosis to import all the OSM data, and it works perfectly.
So I guess that the embedded plugin has some bugs (or maybe I am misusing it).
I presume you are using the Quick OSM plugin, this uses the geojson export parameter of Overpass-Turbo which only returns complete geometries, not the geometries of nodes which make up a way. I believe there are queries which will return the children of a way which may give you what you want.
I’m a little surprised that there isnt an obvious operator in QGIS to merger coincident nodes in a layer. I suspect I’m missing something.