What takes precedence when there’s a discrepancy between a street sign and the government data/base map?
The “DCS NSW Base Map” background layer shows the street name as “Cooper Street”, and this is how it has been mapped so far.
But a photo from Mapillary shows the street sign name of “Coopers Lane”…
Should I change the name of the OSM street to match the street sign?
Hmm, looks like it was mapped as “Coopers Lane” 14 years ago (Way: Coopers Lane (144726898) | OpenStreetMap), but then changed to “Cooper Street” 8 years ago (Way: Cooper Street (144726898) | OpenStreetMap).
The general rule for OSM is that ground truth is the best source, so if the sign is Lane, I’d update it to Lane.
You could use alt_name=* if it’s genuinely referred to by another name, but +1 to ground truth as the name=*.
It would be nice to have a better way to tag the situation in a way that makes it clear that the government datasets use X but the street sign uses Y, for the time being it’s worth adding a note=* about it, so that future mappers that encounter the way have the context.
I think the only exception is when it’s clear the sign has a typo, and sometimes it just matter of informing the council to fix the sign.
I think also worth a mention that the source of the name & alt_name might also be added to the object. eg;
source:alt_name=DCS Base
source:name=Mapillary20Sep2023
Avoids confusion when a later mapper wants to change it to something else and makes Overpass queries easier.
OBTW looks like the laneway has been paved as well. I haven’t been there for a few years.
In my experience over some years, where there is a descrepancy, it is always the DCS NSW Base Map that is incorrect. This is because the Base Map is frequently not updated when changes occur and it continues to show old information, in one instance information that had been changed forty years ago. There does not seem to be a systematic way for the Base Map to be updated. I was told that local government authorities are able to initiate updates but sometimes they change signs, names etc. but don’t initiate updates on the Base Map. Further, in two rural LGAs, I have seen waterways which were signposted with names different to the Base Map. In regard to street names, the NSW Address Location Service is nearly always correct for street names and it is a better source for accuracy than the Base Map. This is because it is perceived as necessary to ensure emergency services will always be able to locate any specified address. About a decade ago, when OSM was given permission to use NSW Govt date, the Address Location Service was one of the datasets included but it is not as easy to access. Overall, if there is a discrepancy with the Base Map, rely on the other source as most likely to be accurate.
ADDITIONAL COMMENT:
When I use “Street” in the NSW Address Location Service, using the URL below, it returns an accurate result:
When I use the “Lane” as in the following URL, it returns a corrected response showing the correct address as Cooper Street:
Thus, using the NSW Address Location Service as a reliable source, “Cooper Street” is the name that emergency services would look for. As LGAs are the ultimate authority on street names (except for highways), an enquiry to the local Council would provide the definitive answer.
I generally go by the street sign, as I’ve seen several errors in the DCS Base Map in the past. That’s not a strict rule, occasionally the sign can be wrong. Example Way: Apple Tree Hill Drive (35098896) | OpenStreetMap - was been ‘Drive’ when I lived nearby in the 1970s-80s, new sign in 2014 had ‘Rd’, replaced in 2015 with a sign with ‘Dr’. Last couple of visits (last visit April 2026) I’ve seen another new sign, with ‘Rd’ again!
