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Border between countys is not correct [closed]

+3 votes
97 views

Hello,

on the map is a missing part that belongs to nothing. So some of the caches count to the western county (Bremerhaven/Bremen) but they belong to (Wesermarsch/Niedersachsen).

For example: http://coord.info/GC4DHFY

How can that be fixed? Is there any function to report caches that a wrong in counting to county or country?

Hope the screenshots may help to see what i mean.

Merry X-Mas

closed with the note: Problem is solved if it gets poly with more details.... No further answers needed..
asked Dec 21, 2015 in Bug reports by GrafZahl75 (1,260 points)
closed Dec 22, 2015 by GrafZahl75
The polygons on the maps is simplified versions to speed up the webpage as described in the text at the top of the page. They are not used inte the calculation of where the cache is.
But it might still be incorrect. The borders on the OSM map might be the one that are used and they are on the wrong place on them to. OSM is often the source of polygons to PGC but other data might be used.
If a official polygonset is provided  government the borders the caches might be in the correct region and OSM is wrong. Or an old OSM data is used and it has changes
So are you sure the caches are in the wrong region?

Borders on maps can differs especially on water. It might even be the case that the border is the deepest part of the river and it will move over time. There are islands on the border river between Sweden and Finland that changes country from time to time. The official border is determined every 10 year and they have change country a couple of times
The two caches on the river in the first screenshot count to Bremerhaven/Bremen. In the Listing they are marked correct belonging to Niedersachsen. As you see on the last screenshot if you look on the county map Germany without a region selected you might see that there are areas without belonging to a county. But the county border is the "Dotline" . So a Niedersachsen cache is counted to the region  Bremen.. Its not a big mistake but Bremen is very small and every Cache counts...

Maybe i cant help to fix the polys if i know what ist needed to do so.
The borders on the last map is the simplified as described on the page and do not represent what is looked for to determin where a cache is.

I would not  trust what the CO tags the caches as near the border. I have seen alot of incorrect tagged caches. And border sings along road that are misplaced.

The might just have choosen where the physical cache is and have not looked at the question mark on the map. Or they have looked on an incorrect map. Google maps have for example alog of errors han have had borders in Sweden 12 km from the real place.

The bordet you look at on the map is the border on the (OSM)OpenStreetMap and it is not necessary correct. An official map has to be looked at to determin the true border. In Sweden pgc don use OSM because they are not always correct but uses a goverment source that is correct by definition.

PGC might use a source like that in Germany.
OSM is a map created by the users and they might not have the legal right to use the official border and they might be recreated from aerial photography and field observation and might be incorrect. expecially on a river.

1 Answer

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Best answer

As mentioned above, and on the Map counties page, the borders you see on the map there are simplified. What this means is that they might be built upon a thousand points instead of a million. This is to make it more usable and faster in the web browsers. Ultimately we would use better polygons when zoomed in, but we don't.

When calculating where the geocaches belong, we however use the best data we can and have access to. For most countries, this is data from Openstreetmap. The data is not extracted live or automatically, so quite often we might have over a year old data. Borders normally don't change, but sometimes Openstreetmap changes their data to the better.

I took a closer look at http://coord.info/GC4DHFY since you mentioned it specifically (which is great). I will attach a screenshot from Openstreetmap, where I have added a marker at the coordinates of the geocache.

(right click the image and open in new tab to see it in full size)

As you can see, the marker is on the west side of the border in the river, according to OSM, our source. Now I didn't look up which county is which, and I don't know German geographics down to that detail on the top of my head (I am from Sweden...). But you mentioned that you thought it belonged to the eastern county, so I assume this disproves the case.

Then as mentioned in the comments. 100% correct borders are very rare. I am not saying OSM is correct. But it's likely that Google maps is much much worse with their borders, they usually are.

I hope this answers your question. If you want to check other geocaches, visit openstreetmap.org and paste the coordinates as a location to see where the marker ends up. If it's correct there, and wrong at Project-GC, we will look into it, maybe we have to update our German polygon data then.

 

As a side note. For Sweden we do not use Government data since it's not free. We use data from a statistical entity since it seems to be the one that's closest to reality, of the free ones. Lantmäteriet who owns the data in Sweden is changing their policy in 2016, we will see what happens with Swedish polygon data that year.

answered Dec 22, 2015 by magma1447 (Admin) (208,130 points)
selected Dec 22, 2015 by GrafZahl75
OSM is right http://coord.info/GC4DHFY is belonging to Wesermarsch/ Niedersachsen ... But on the PGC map it counts to Bremerhaven/Bremen as you see on my first screen and this isn´t correct. OSM has the correct borders of regions and countys in our area. If i can help with the polys let me know how to do. I close the question now.

Merry Xmas
I think you have confused me. You said in your original post that Bremerhaven was on the western side, but from what I can see it's the opposite.
http://osmose.openstreetmap.fr/en/map/
(ignore the markers, couldn't get rid of them)
Sorry you are right.. I mainly talk german. It counts to Bremerhaven whats is EAST but it should count to Wesermarsch on the WEST. I´ll paint a picture next time .. much easier :-)
Well, honestly, it was very short and clear, except the fact that you mixed up east and west.

Since my last comment, I have been looking at upgrading our polygon data. But most counties have changed name in OSM (added/removed landkreis). Updating the polygon data might have huge effects on all our challenge checkers. We will have to spend some more time looking at the data, so we don't act before we know what we are doing.
We are currently running an update of the polygon data for Germany. The example given will end up in Wesermarsch (Lkr) with the new data. I assume OSM has improved their polygons in the area. It will take many hours before all our data has been recalculated.
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