[talk-au] Import vs filtering query

Little Maps mapslittle at gmail.com
Mon Sep 6 08:27:40 UTC 2021

Thanks everyone for your feedback. I suspect I’m being over-cautious so I appreciate everyone’s expertise. Thanks Steve too for the broader thoughts to consider.

RE: “How would you match the different map set, the government one to OSM? And how will you validate the matching is correct?”

I’m a GIS novice so welcome any suggestions. This is what I’ve done so far, which works well:

1. Open regional subset of Vic gov road data in QGIS. Remove unwanted road types (paths etc) and separate into sealed and unsealed subsets
2. Create a buffer around all sealed gov roads
3. Open OSM roads in a new layer, clip to the buffered sealed gov roads, and save as a new layer. This file contains all the OSM tags so I can easily compare surface tags across both datasets.
5. Filter the data to show only those roads that have a different surface tag in the 2 datasets. Then repeat the process for unsealed roads in the gov dataset.
6. Sort the final dataset from long to short ways and work down the list starting at the longest. I’ll ignore the very short segments, lots of which are analysis artefacts.
7. Edit OSM roads in JOSM as normal.

The method seems to work well so far. The only error I’ve found so far is when a track ran parallel to a main road in OSM, but that became obvious as soon as I opened the data in JOSM. I don’t think there’s any need to validate the matched data beyond this atm but am happy to refine the method. The method won’t work in dense built-up areas but I’m only focusing on non-urban areas. If there’s a faster or more accurate method that doesn’t require coding skills I’ll be keen to try it when I start the next region.

Thanks again everyone, cheers Ian

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