[talk-au] JOSM Scanaerial plugin on NSW LPI layers

Andrew Davidson u887 at internode.on.net
Sat Jan 23 23:11:26 UTC 2016

The work flow that JOSM wants you to use is to have your new data in
one layer and the existing OSM data in another and to "merge
selection" on individual items.  I'm assuming this is to slow down
people just dump-and-running. I found it useful to use the merge
approach as you can delete the ways from the kml layer as you do each
one and it lets you check that you've processed each way. 

----- Original Message -----
From: "Nev Wedding" 
To:"OSM Australian Talk List" 
Sent:Sat, 23 Jan 2016 12:42:53 +1000
Subject:Re: [talk-au] JOSM Scanaerial plugin on NSW LPI layers

 (corrected message….opening the .kml fileI have the .kml file and
the downloaded osm data as seperate layers and want to upload the .kml
layers which contains all the updated info)

I have followed this process for Kooyong State Conservation Area which
has gone well after opening the .kml file and have simplified and
added all the tags, …but on trying to upload the final boundary I
get this ominous message
“You are about to upload data from the layer 'Kooyong.kml'.
Sending data from this layer is STRONGLY DISCOURAGED. If you continue,
it may require you subsequently have to revert your changes, or force
other contributors to.
Are you sure you want to continue? 
 I assume the warning is to dissuade mappers from careless import of
large uncorrected datasets.? 
 Sooo…, am I ok to continue or is there another reason?  ..I am
on-hold here until I see a reply 

 On 22 Jan 2016, at 11:36 PM, Andrew Davidson  wrote: 
You can extract the geometries from the database directly, you don't
have to scan them. I tried this on three park areas to see how much
work was involved. The recipe I followed was:

1. Use the query tool to find out how many objects have the name that
you are looking for. You do this with:


with the return format set to html. Names must be in upper case and
you need to see what object ids are returned. For example if you
search for Yanununbeyan with:


You get three different ids (198,208,1131) because there is a
Yanununbeyan State Conservation Area, Yanununbeyan Nature Reserve, and
Yanununbeyan National Park. All of which need to be tagged
differently. Follow the object links to find out what type of area
they are.

2. Having found the object id you need you get the geometry by using
the query tool and setting the object id, setting the output spatial
reference to 4326 (WGS84), and changing the output format to JSON.

3. Save the resulting page, say output.json

4. Use ogr2ogr from GDAL to convert the output into something JOSM can

ogr2ogr -f "KML" output.json output.kml

5. If you have the opendata plugin installed you can open output.kml
in JOSM.

6. Use the simplify way option in JOSM as there are far too many
points in the resulting kml. I personally thought that the default 3m
looks OK.

7. Tag the ways with an appropriate source:geometry and add a note to
the effect that the way has been simplified using a max error
criterion set to whatever you used.

8. Now comes the difficult and time consuming bit. You have to cut up
and conflate the new boundaries with the existing data as you merge
each new way from the layer you opened the kml in to the layer the osm
data is in. This is the step where you could really make a mess. 

I found while doing the few test cases that I had to:

- Make sure that common boundaries use only one way (which means that
the more parks, state forests, admin areas, etc that share ways the
more time consuming it gets)

- Make judgement calls about if you should use the new boundary or
keep the existing way where the boundary is something physical on the
ground like a river bank or coastline. This is why I tagged the new
ways with source:geometry so other mappers can see where they came

- If there are already ways in place, using the replace geometry
function of the utils2 plugin to try and preserve history.

The cases I tried as a test were:

South East Forest National Park:

Murramarang National Park:

Clyde River National Park:

The South East Forest case was a multi-hour mapping marathon as the
park has a lot of separate sections and shares many boundaries with
neighbouring state forests and parks. The other two were much simpler
but Murramarang need more time than Clyde River as it has more
sections and shares a lot of common ways with the coast and various

As to the import question it seems to me that there is a tacit
agreement that tracing the boundaries one at a time is acceptable (not
sure what the rest of OSM would think about this). Given that the
biggest problem with an import would be conflating the data with the
existing, provided that we're carefully hand-crafting each park I
think we're OK. Does anyone have a differing opinion?

On Tue, 19 Jan 2016 13:44:12 +1000
Nev Wedding  wrote:

Should the JOSM Scanaerial plugin be able to scan the LPI NSW
Administrative Boundaries NPWS Reserve WMS layer and others. I would
like to zoom in to a section and use the plugin as an initial pass
instead of manually mouse clicking around the long and winding
boundary and then refine the result before tagging and uploading.

I am using a mac OS X and there are no instructions for that install
so I may not have it set up correctly yet, so first up before
proceeding further, I would like to know if it will help anyway. 

I am unfamiliar with tracing shapes other than tediously wandering
around the boundaries one click at a time.

I played around with Gimp and Inkscape but found that to be quite a
task too and wasn’t sure if I could use the output in Josm in

How do you manage such tasks? Are their special mouse tools available?

Is what I am trying to do essentially considered to be part of an
import and/or the current LPI layers unsuitable for the tracing

Some links to where to find more info on this topic would be
appreciated. _______________________________________________
Talk-au mailing list
Talk-au at openstreetmap.org

Andrew Davidson 


[1] mailto:u887 at internode.on.net

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk-au/attachments/20160124/7c7cb2c4/attachment.html>

More information about the Talk-au mailing list