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Virtually all, if not all, highways on the islands of Savai'i and Upolu in Samoa show up on KeepRight as Floating Islands - This way is not connected to the rest of the map - like this example

Is this because Samoa is an island without mapped transport links to other parts of the world? Is there some basic tag missing from the islands? Larger islands such as New Zealand or the United Kingdom don't seem to suffer from this problem!

How can I or someone else correct this?

asked 30 Apr '15, 11:26

NZGraham's gravatar image

accept rate: 17%

edited 30 Apr '15, 19:10

aseerel4c26's gravatar image

aseerel4c26 ♦


If they're false positives, and the problem doesn't occur elsewhere, I'd just mark them as such in keepright and not worry about it.

(30 Apr '15, 11:29) SomeoneElse ♦

That seems to be the reason. However marking all these reports as false positives will be a lot of work, especially since there could be a few true positives among them. Of course you can just ignore all of them by unchecking "floating islands" on the left.

(30 Apr '15, 12:33) scai ♦

For what it's worth, I've always found the maintainer of keepright extremely helpful when dealing with the (rare) issues that crop up on the site. You could perhaps mention it to them too; but personally I'm not sure that "unconnected roads on islands are identified as islands" is such a serious issue.

(30 Apr '15, 13:05) SomeoneElse ♦

Thanks for all the suggestions. I've emailed KeepRight asking for comments. I mentioned that my main concern was that all the false positives could well obscure some genuine unconnected highways. I'll post their answer here in due course.
Just trying to improve things where I can.

(01 May '15, 04:35) NZGraham

Here's the answer from Harald at KeepRight.......

"thank you very much for pointing me to that question!

in fact there is a list of starting points in the source code of the islands check, just about 140 locations from around the globe I picked randomly. The check successively finds ways connected to the ways already known and step by step tries to reach the whole planet. It includes ferries so the program may travel across the sea if the ferry is connected to the network of highways at a junction node.

Looks like as if there is no ferry to Sāmoa drawn in OSM. In this case I have to add a well known starting point to the check. The ferry line connecting the two islands is drawn correctly so only one new starting point should suffice. In a few days the error markers should disappear and make the islands check useful for Samoa"

I'll check when KeepRight is next run and see how things look. I'm really impressed by how everyone is keen to improve things and help solve any issues with OSM. Great teamwork!

permanent link

answered 04 May '15, 07:10

NZGraham's gravatar image

accept rate: 17%

yeay, my guess was right. :-) Thanks, NZGraham! and Harald!

(04 May '15, 13:56) aseerel4c26 ♦

Excellent! Harald's tweak to KeepRight or OSM has worked. There are still several 'unconnected ways' on both islands but these are likely genuine errors which merit some on the ground investigation by any mappers who might be visiting Samoa. At least they are now clearly identifiable and not obscured by 'noise'.

(08 May '15, 22:19) NZGraham

Yes, I guess the missing transport links (I guess only ferries / bridges) are the cause, although I do not know why it does not show up for New Zealand. Maybe NZ is entered as a new start point for the accessibility search in keepright, but doing so for every small island is likely too much work (also happens near Scotland mainland). E.g. for Great Britain there are many many ferry connections mapped.

I would suggest to just switch off this check category when you want to use keepright on those islands.

permanent link

answered 30 Apr '15, 12:46

aseerel4c26's gravatar image

aseerel4c26 ♦
accept rate: 18%

That link's to St Kilda, and I don't see any ferry connections there. I don't see keepright "island" issues flagged where there are ferry connections (e.g. on the Outer Hebrides to the southeast) except where genuine.

(30 Apr '15, 13:07) SomeoneElse ♦

There are no ferry connections to St Kilda. Getting on or off by boat is exceedingly chancy at the best of times. Last person I knew who went there was stormbound & they were eventually taken off by RAF helicopters.

(30 Apr '15, 13:55) SK53 ♦

@SomeoneElse: yes, I also do not see mapped ferry connections to this Scottish island and I see a "floating island" warning on every highway there. If there simply are no ferry connections (SK53), then, I would just switch off the warning category as I do not think that the keepright devs can make an exception for every small island. Maybe(!) it would be useful to map something like reachable_by_ferry=no / really_no_ferries_to_this_island=yes on the coastline or to help tools like keepright (could start a new accessibility analysis then)

(30 Apr '15, 14:18) aseerel4c26 ♦

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question asked: 30 Apr '15, 11:26

question was seen: 3,966 times

last updated: 08 May '15, 22:19

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum