New Popular Edition in JOSM

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New Popular Edition in JOSM

Nick Whitelegg

I would like to announce the addition of New Popular Edition support to the
landsat plugin in JOSM. It works in exactly the same way as Landsat; you
select New Popular Edition when you're downloading, and when the image has
downloaded you can adjust its position with the same toolbar button as for
adjusting the position of Landsat.

Due to changes I made in JOSM itself, and the addition of a third party
library to convert between OSGB gridrefs and WGS84 lat/lon (Jonathan Stott's
jcoord) you need a special version of JOSM to run this. This is available at

http://www.free-map.org.uk/downloads/josm/josm-1.4-nw2.jar
http://nick.dev.openstreetmap.org/downloads/josm/josm-1.4-nw2.jar

Source tarballs of the modified version of JOSM are available from the same
locations.

The landsat plugin (it's still called landsat even though it supports NPE
too... maybe it should be renamed 'wms') that you need is available at:


http://www.free-map.org.uk/downloads/josm/1.4-nw2/landsat.jar
http://nick.dev.openstreetmap.org/downloads/josm/1.4-nw2/landsat.jar


A few points to note:

* You'll probably want to make your colours darker and line widths wider in
elemstyles.xml or in the preferences, so that they show up better against the
NPE background.

* Due to the NPE alignment issues you probably will have to adjust it
slightly. You should look at several roads in the area to make sure they're
all reasonably well aligned.

* It is a little slow so a reasonably fast machine is recommended.

* I've used the source=npe tag when creating ways from NPE maps.

Nick

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Re: New Popular Edition in JOSM

David Earl


> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of Nick Whitelegg
> Sent: 12 November 2006 11:11
> To: [hidden email]
> Subject: [OSM-talk] New Popular Edition in JOSM
>
>
>
> I would like to announce the addition of New Popular Edition
> support to the
> landsat plugin in JOSM.


This is excellent again, thank you.

But now I'm a bit worried. The tracks in my area don't align. (And no, it's
not changes to the street pattern!) If I move the NPE maps to align on a key
point, then they quickly diverge in all directions from the point. Most of
the nodes are mine, but not exclusively, and mine have always joined up with
other people's in my area remarkably accurately. The River Cam was traced
(not by me) from Landsat, and taking into account the Landsat translation
which I've now mostly corrected, that doesn't match either.

I *think* it is nearly all scale (at least in a small local area), not
rotational. It's nearly all (though not completely) a North-South
difference, amounting to maybe 50m in 1500m, but the north-south divergence
gets greater the further east of west you look from the point as well as
north or south, i.e. while the difference is mostly a vertical misalignment,
it gets worse the further you go in *any* direction.

(The grid squares on the NPE layer are also elongated vertically)

Should I be worried about all the data I've entered? Can I use the NPE layer
for anything useful with any confidence?

David


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Re: New Popular Edition in JOSM

Nick Burch-2
On Sun, 12 Nov 2006, David Earl wrote:
> If I move the NPE maps to align on a key point, then they quickly
> diverge in all directions from the point.

As a general rule, a given NPE calibration is only valid for about 2-4km
from that point. It is also only valid on a given sheet - if you cross
sheets, it'll probably be wrong

When tracing to a gpx (http://gpx.npemap.org.uk/), calibrating on grid
square joins, I do find that the error changes as I move a few squares.

> Should I be worried about all the data I've entered? Can I use the NPE
> layer for anything useful with any confidence?

I'd try tracing it to a GPX file (having calibrated!), and comparing that.
You might just be unlucky, and be using a map that was distinctly off-flat

Nick

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Re: New Popular Edition in JOSM

Nick Whitelegg
In reply to this post by David Earl

> > I would like to announce the addition of New Popular Edition
> > support to the
> > landsat plugin in JOSM.
>
> This is excellent again, thank you.
>
> But now I'm a bit worried. The tracks in my area don't align. (And no, it's
> not changes to the street pattern!) If I move the NPE maps to align on a
> key point, then they quickly diverge in all directions from the point.

I'd be surprised if it's that bad - maybe it's an issue with that particular
NPE map. Earlier today I got good alignment in an approximately 5km x 5km
area on one NPE tile, and 2km x 2km on another.

> Most
> of the nodes are mine, but not exclusively, and mine have always joined up
> with other people's in my area remarkably accurately. The River Cam was
> traced (not by me) from Landsat, and taking into account the Landsat
> translation which I've now mostly corrected, that doesn't match either.

> I *think* it is nearly all scale (at least in a small local area), not
> rotational. It's nearly all (though not completely) a North-South
> difference, amounting to maybe 50m in 1500m, but the north-south divergence
> gets greater the further east of west you look from the point as well as
> north or south, i.e. while the difference is mostly a vertical
> misalignment, it gets worse the further you go in *any* direction.
>
> (The grid squares on the NPE layer are also elongated vertically)
> Should I be worried about all the data I've entered? Can I use the NPE
> layer for anything useful with any confidence?

I guess Nick Burch's reply answers this, and his reply mirrors what I've seen
- the further you go from the point of alignment, the more 'off' it is. I
would say that as long as you align the NPE map with existing OSM data within
2-4km of the feature you want to add using the NPE layer, it'll be fine. To
that end it works best if you want to fill in information in area where there
is already OSM data.

I think I did all the projection code correctly (used a third party library).
If anyone does think it's a projection error the code which does the
projection is in SVN under
utils/josm/plugins/landsat/src/landsat/OSGBImage.java.

Nick

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Re: New Popular Edition in JOSM

Tom Chance-2
Ahoy,

On Sunday 12 November 2006 19:28, Nick Whitelegg wrote:
> > But now I'm a bit worried. The tracks in my area don't align. (And no,
> > it's not changes to the street pattern!) If I move the NPE maps to align
> > on a key point, then they quickly diverge in all directions from the
> > point.
>
> I'd be surprised if it's that bad - maybe it's an issue with that
> particular NPE map. Earlier today I got good alignment in an approximately
> 5km x 5km area on one NPE tile, and 2km x 2km on another.

Just to say that I emailed Nick because I had the same problem in St Albans
when I very carefully align it in a particular area and it is completely off
not far from there:
http://tom.acrewoods.net/files/josm-npe.png

It happens in quite a small area, though it looks like a slight fold in the
paper might be partly to blame. It does also happen in small residential
areas, though, where some roads just seem wrong. Ah well, it's useful for
some things and looks really good, and I'm sure it's not a projection issue
on Nick's part since it would have to look obviously distorted if it were.

Regards,
Tom

--
The struggle against power is the struggle of memory against forgetting
 - Kundera

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Re: New Popular Edition in JOSM

Nick Burch-2
On Sun, 12 Nov 2006, Tom Chance wrote:
> It happens in quite a small area, though it looks like a slight fold in
> the paper might be partly to blame. It does also happen in small
> residential areas, though, where some roads just seem wrong. Ah well,
> it's useful for some things and looks really good, and I'm sure it's not
> a projection issue on Nick's part since it would have to look obviously
> distorted if it were.

What you probably want is a mode when you can see the tile edges. If the
tile edges remain the same distance from the grid lines over an area, then
you know you're calibration's file. If the tile edges and the grid lines
change their relative distances, you'll know you need to re-calibrate.

Oh, and if your tile edges overlap with the grid lines, then those tiles
are already prefectly calibrated as it is :)

(Figuring out the distance from tile joins to grid square joins is how the
gpx tracer does calibration)

Nick

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Re: New Popular Edition in JOSM

Nick Whitelegg-2
In reply to this post by Tom Chance-2
>It happens in quite a small area, though it looks like a slight fold in
the
>paper might be partly to blame. It does also happen in small residential
>areas, though, where some roads just seem wrong. Ah well, it's useful for
>some things and looks really good, and I'm sure it's not a projection
issue
>on Nick's part since it would have to look obviously distorted if it
were.

To give an idea of the sort of things it's useful for: I used it to fill
in several country lanes in various 2-4km x 2-4km areas (or so) where the
main roads, and most of the footpaths, have already been done. Thus it's
likely to be of particular use for both main-road and footpath surveyors
who might not have time or inclination to do every country lane.

Indeed, as long as I'm careful with the alignment I can see that I could
use it to fill in all the country lanes between here (Southampton) and
Winchester.

Nick




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Re: New Popular Edition in JOSM

Simon Hewison
In reply to this post by Nick Whitelegg
Nick Whitelegg wrote:
> I would like to announce the addition of New Popular Edition support to the
> landsat plugin in JOSM. It works in exactly the same way as Landsat; you
> select New Popular Edition when you're downloading, and when the image has
> downloaded you can adjust its position with the same toolbar button as for
> adjusting the position of Landsat.
..

All very good, and incredibly useful. However if you start looking at
the Western extremities (e.g. Pembrokeshire), you will find that by
about 5 degrees west, the difference between Grid North and True North
becomes so great that even within a 1km square, that the tiles really
need skewing to fit the JOSM display.

(Either that, or JOSM needs an option of OSGB projection as well as
Mercator or EPSG:4326), which of course wouldn't make much sense outside
the UK.

--
Simon Hewison

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