[OSM-talk] cooperative mapping

Jeffrey Martin dogshed at gmail.com
Sun Aug 12 12:58:26 BST 2007


Bogus points:
How do we know which points we can throw away? I remember
a similar question in my Analytical Chemistry class. I don't
think the professor ever gave us a good answer but some
data just looks wrong.

My first day with the GPS I had two sets of bogus points.
There's a big bunch that are too far apart to see a path.
Maybe I had the sample rate set too low or maybe being
at my desk and getting signals through the window messed
it up.

Later there was a rainstorm and
I took shelter in the doorway of the grocery store. I could see the
location walk all over the screen while I was standing still. Someone
else said he routinely takes off the first points collected before
the GPS has settled down using a text editor.

Lines for tracks:
I was converting the gpx files to osm files in JOSM to get something
I could edit. This also give me arrows, but JOSM warns me that
I shouldn't upload them to the server. That was a way I found doing
a google search. There may be a better way. I wish I could select
points in order. The straight line selection almost does this. I guess
what I want is a curved line selection.

Layers:
I noticed that having layers is a new feature in JOSM. I suppose
having layers on the server is probably the most obvious way
to do what I'm talking about, but there might be other ways.
Filtering based on an attribute?

Notes:
I don't take meticulous notes, but if I were to put my notes
into the database when I get home I would probably add
more detail.

Data standards:
Years ago before HTML really took off I read up on SGML. The basic
idea is that you separate the markup from the information.

>From what I understand of the process you design the structure
of the data in the document and then maybe a week later or
30 years later someone writes software to deal with the data.

If I start to standardize my notes then that would increase
accuracy. For example I could label two points bridge beginning
and bridge end, and then add attributes like bridge type, bridge subtype,
number of lanes etc. A person could use this information to draw the
bridge but later maybe software could.

>From posts I've seen on the mailing list this looks like where
people are already trying to go. I've seen discussions of
standard ways to build roundabouts and intersections. If
we first come up with a standard way to describe these
things then the discussion of how to build them is easier.

Layers on the server:
For a first step how do I get support for layers added to the server?

On 8/12/07, Tom Hughes <tom at compton.nu> wrote:
>
> In message <bf60a2e10708112056r64a85737s1a963a7faf4e3119 at mail.gmail.com>
>           "Jeffrey Martin" <dogshed at gmail.com> wrote:
>
> > The data collector upload tracks with bogus points edited out.
> > (I figured out how to do this, but it's not easy.)
>
> I'm not quite sure what counts as a "bogus point" or how you would
> identify one - gpsbabel can do filtering based on DOP if you want to
> get rid of points where there was accurate fix, but in my experience
> it isn't that helpful.
>
> So you could upload gpsbabel filtered traces if you wanted.
>
> > The tracks display with arrows so one can see where the data collector
> was
> > going and what direction.
>
> You can get josm to join up the GPS points if you want. I'm not sure
> if it draw arrows or lines though, as it isn't a feature I ever use.
>
> > The data collector uploads waypoints with notes for points or groups of
> > points.
>
> An interesting idea. I look forward to somebody providing a path to
> implement it ;-)
>
> > When JOSM downloads from the server it should download this raw or
> semi-raw
> > data as separate layers from the mapping data. This way the mapper can
> go
> > back and forth between the two without having the notes and such clutter
> up
> > the finished product. Also, the mapper doesn't have to go back and
> delete
> > waypoints from the finished product. The notes are still available for
> > review.
>
> GPS data is already downloaded in a separate layer, and I imagine that
> if GPS waypoints were supported they would also be in a separate layer.
>
> Tom
>
> --
> Tom Hughes (tom at compton.nu)
> http://www.compton.nu/
>
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>



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