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#1 2014-03-11 02:58:57

frasty
Member
Registered: 2013-12-25
Posts: 10

JOSM: skewed ways with alternative projection

Hi all,
I need to use EPSG:3003 projection with JOSM.
Being that a non-predefined projection, I enabled the Proj4J plugin and aftewards selected EPSG:3003 on the projection menu.
Unlikely, everytime I load josm with that projection, many ways and areas appear skewed.
How could I overcome this problem? Do I have to wait for EPSG:3003 being included as a predefined projection?
Thanks

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#2 2014-03-11 15:48:04

Tordanik
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From: Germany
Registered: 2008-06-17
Posts: 2,708
Website

Re: JOSM: skewed ways with alternative projection

frasty wrote:

Unlikely, everytime I load josm with that projection, many ways and areas appear skewed.

Can you perhaps show us a screenshot of that? It's hard for me to imagine how it looks.


OSM in 3D: OSM2World

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#3 2014-03-11 19:07:49

frasty
Member
Registered: 2013-12-25
Posts: 10

Re: JOSM: skewed ways with alternative projection

Here are the two screenshots. The first is with standard mercator projection, whereas the second is with EPSG:3003 projection.
As you can see in the second screenshot many ways appear skewed and they do appear differently skewed every time I restart JOSM with EPSG:3003.

Last edited by frasty (2014-03-11 19:08:50)

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#4 2014-03-12 18:52:08

Tordanik
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From: Germany
Registered: 2008-06-17
Posts: 2,708
Website

Re: JOSM: skewed ways with alternative projection

Thanks for the sceenshot, your problem is clearly visible there.

Unfortunately I have not encountered an EPSG:3003 map before, but are you sure that the result is incorrect? Some of the built-in projections in JOSM will also cause buildings to look skewed, but I understand those are actually correct results because of the properties of these projections. For example, when WGS84 was the default setting in JOSM, many users were confused when rectangular shapes in JOSM did not look rectangular on the map - and vice versa.


OSM in 3D: OSM2World

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#5 2014-03-14 04:07:30

frasty
Member
Registered: 2013-12-25
Posts: 10

Re: JOSM: skewed ways with alternative projection

Thanks for your reply.I am pretty sure that this is not the correct way a projection should look like. As you already pointed out, OSM data loaded with a WGS84 projection might look weird in the first place.
I am aware that this is how a projection is expected to work, though. Conversely, with EPSG:3003 shapes and also simple ways appear misaligned and sometimes intersected.
To demonstrate this further I add two new screenshots depicting the same area around the same building=train_station:
The first one is taken by loading a 1000km2 slippy map.
The second one is taken by loading a much larger area.
As you can see in the second screenshot, ways representing the same area appear more misaligned.
So, to me EPSG:3003 projection doesn't seem to draw correctly and this is clearly visible by loading OSM data from a large slippy map rather then a small one.
I am afraid to do some editing with EPSG:3003 but I have to use that because in the need to overlay some local WMS data using that projection (wms data is drawn correctly in EPSG:3003).

Last edited by frasty (2014-03-14 04:09:37)

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#6 2014-03-14 06:33:59

JRA
Member
Registered: 2007-12-17
Posts: 676

Re: JOSM: skewed ways with alternative projection

Hi,

Looks odd and is perhaps a JOSM bug. Perhaps better to continue on josm-dev list or make a JOSM bug report.

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#7 2014-03-30 00:38:59

Tordanik
Moderator
From: Germany
Registered: 2008-06-17
Posts: 2,708
Website

Re: JOSM: skewed ways with alternative projection

Has there been some progress on this in the last two weeks? I agree with JRA that a JOSM bug report would be the way to go.


OSM in 3D: OSM2World

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#8 2014-04-01 21:52:10

bastik
Member
Registered: 2011-08-05
Posts: 58

Re: JOSM: skewed ways with alternative projection

EPSG:3003 is supported in JOSM core:

(1) go to Preferences > 3rd Tab > Map Projection > Custom Projection
(2) enter

+proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl +wmssrs=EPSG:3003

into the text field

You can open a ticket at the JOSM bug tracker so it is added to the list of build-in codes.

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#9 2021-04-07 21:54:06

frasty
Member
Registered: 2013-12-25
Posts: 10

Re: JOSM: skewed ways with alternative projection

Sorry to chime in after so much time, but the issue is still unresolved.
Adding the custom projection defintion above didn't lead to a better alignment.
Here is a screenshot with OSM data layer over a local WMS source (EPSG:3003). As you can see, the OSM data layer is shifted more than 70m NW:screenshot

Do I need to file a bug?
thank you

Last edited by frasty (2021-04-07 21:57:00)

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#10 2021-04-08 12:45:52

skyper
Member
Registered: 2020-06-08
Posts: 322

Re: JOSM: skewed ways with alternative projection

frasty wrote:

Do I need to file a bug?
thank you

Yes, don't be shy and, please, use the build-in "Report Bug" item from the "Help" main menu in JOSM. Thanks

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#11 2021-04-28 17:24:34

skyper
Member
Registered: 2020-06-08
Posts: 322

Re: JOSM: skewed ways with alternative projection

I just recheck without the proj-Plugin and EPSG:3003 is available in core:
Go to Preferences -> Map Projection and choose "Projection Methode"="By Code(EPSG)" and search for "3003".

If the problem is still present, please, create a new ticket.

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