[talk-au] Discussion E: how to find faults in maps

Herbert.Remi Herbert.Remi at protonmail.com
Sat Sep 28 21:30:51 UTC 2019

# Discussion E: how to find faults in maps

## The Issue

The ACT has 3000km of roads, 2000km of footpaths, and 329 km of shared bike paths, 1000s of km of formed trails (2/3 the state is rideable), a few 100kms of mountain biking "single-track" and a few dozen active planners at best. How do you find errors in this network?

It is looking for a needle in the haystack. Here are some options I have tried, and I would be grateful for further suggestions. Going there or comparing with the satellite photos in OSM are two options that I will not mention further here as that is the way they are a map in the first place. Unfortunately, it is not enough. The ACT maps require quality and consistency improvements.

FIXME has not been all that helpful, with errors in the ACT in the dozens and not 100s or 1000s. FIXME is just the errors we know of not the ones we don’t.


What are the approaches you have used to find errors, particularly with tagging?

What follows are options that I have helped, that you might like to comment on.

## 1. Detection algorithms

Not surprising somebody has written code to do this – an OSM proofing tool. It is good for some things and completely misses others. It allows you to inspect OSM in different ways: geometry, tagging, places, highway, areas, coastline, routing, addresses, water, public transport stops and public transport routes. It fishes out all the FIXME tags too. The service is provided by Geofabrik. The website is in English as well. Take a look at it here.


## 2. A different perspective (alternate rendering)

The testing of a map helps. Try using the OSM data and see if it is fit for purpose. We are familiar with the Mapnik rendering (default). It is a general-purpose map. A map for riding bikes, hiking or mountain biking would look different. We can easily forget every Mapnik cherry picks OSM for information. Errors that don’t show on the Mapnik render may show on a bike map. Similar information may be shown differently or keys/tags displayed that are not visible on the Mapnik.

## Interesting render options

To make things challenging, there is more than one type of cyclist. I would like to distinguish between the type of riding mountain bikes do and that of other cyclists. Mountain bikes are built for unpaved and rough surfaces. Other bikes are only suitable for paved and relatively smooth surfaces. I will categorise these city bikes (just a label, please don't take offence). Mountain bikers and city bikers have different needs and their maps should reflect that.

The following websites have English language pages too. Look for the British flag if you end up in the wrong spot.

### CyclOSM for city bikes

CyclOSM is cyclist map and best suited for reviewing the OSM data for city bikes but show unpaved tracks and paths too. There are better maps for mountain biking though. This map can show inconsistent tagging of paths and relations. The tagging issues are raised in the post *Discussion D: mapping ACT for cyclists – complying with ACT law*.


This map is updated continually (live) from OSM and you can see editing changes just minutes after you save them. I have run this map and the ID editor in split-screen so that I could compare the two.

### openMTBmap for mountain bikes

If you ride a mountain bike you will like openMTBmap. This map is rendered for the off-road rider and shows the condition of tracks, permissions and other useful features (check website for details). Unfortunately, there is no live view of these maps, but you can download them for free and view them with BaseCamp from Garmin. If you like the map you can even save it on your Garman device and take it with you. Turn-by-turn navigation on a mountain bike, no problem! Maps are updated weekly. Openmtbmap is rendered for Garmin outdoor devices and looks a bit weird in HD.


I welcome your comments.

keywords: Australia, ACT, FOSS; website, rendering, mountain biking, city biking, Garmin, error detection, FIXME, speciality maps
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