@manings I think that there are problems here that you are not thinking of. * Change set comments and OSMCha become mapper death squad tools, if we only show up when a new mapper does something bad. * How about using thank you for your contribution even if it is not the most stellar edit? * You come off creepy, when you follow new mappers around changing their edits. * I don’t think that you not engage most new mappers in a conversation with this type of workflow. Think about it. A new person joins up and makes an edit. Big brother shows up and the other shoe falls. If the mapper is timid, then they may become embarrassed that they made a mistake. OSM may never see another edit from that mapper again.

The [Simple 3D Buildings[(http://wiki.openstreetmap.org/wiki/Simple_3D_Buildings) page has all the information on detailed mapping of buildings. roof:colour=* is what you are looking for.

This way in change set says “build = 2.2-18-g514f0d2 created_by = Potlatch 2 version = 2.2”. I’ve cleaned us similar problems in the metro Phoenix area using the great Keepright tool. Gasp! Some of those were created by me as an early mapper. I now use the JOSM grid of ways plug-in to create a network of ways as was attempted in the way above from your example area. I also select an intersection and use j then m Josm commands in sequence to make sure that ways are connected.

The overlapping long looping ways from your example, connectivity issues, and the like tend to originate from Potlatch based on my observations. However, anyone of any level of experience will make mistakes. What is nice about OSM are the number of tools to help find and correct these problems. The challenge is to help encourage and develop new mapping talent. The way I have been discussing from your example is still a very valuable contribution that filled up a blank spot on the map!

Regards, Greg

Your post brings up an issue that I have been thinking about. The arm chair mapper page makes it sound like GPS mapping can do no wrong. Your pictures of your traces and my experience point to revisions that need to be made to this article. There needs to be a similar article about issues with GPS mapping. Neither of these techniques are perfect but add to better maps.

I went out with two devices in order to GPS a new road that is being built in the Phoenix Arizona USA area.. I had already roughed in the road and multi use foot/cycle path and wanted to improve road. Moreover, the area is in a desert preserve. There were no buildings to provide echo problems or other GPS interference problems. Also both the units were on external battery sources. The Etrex Vista cx GPS unit was on the shoulder strap of my water backpack. I was taking pictures with the HTC phone GPS with keyboard mapper running. I averaged the resulting two traces while improving the roads in JOSM because there were wide variations in the two traces.

Things I now do, have experienced, or understand:

• I zoom in as far as I can when tracing aerial imagery. If you are at zoom 0, there’s no way you can correctly place a point on Phoenix Arizona, for example. Note that the Yahoo aerials where not as hi res as Bing is. The difference in resolution could cause many accuracy problems while tracing imagery in the past compared with today’s available imagery. This could be one of the reasons that tracing has gotten such a bad name.

• If you trace a GPS path at at zoom 0–some high level zoom–then you will have the same issues as tracing low res imagery.

• Microsoft being Microsoft has its map failures along with its software failures. I don’t want to sound unthankful here. I want to thank MS for the use of their imagery as one of my mapping tools. If I trace, say, a building in the Phoenix area, I can get in nice and close. The building is nice and square. However, the low level image is not the same place on the earth as the newer 2011 images in the Phoenix area. I have to move the resulting trace around to where the building is in at higher zooms. This provides me with doubt about what I am doing at times. Not only are the there image registration issues, there are different years at super low zoom levels. The resulting map is still useful, however. I have had the chance to use OpenLayers to overlay to OSM tiles over other imagery. The traced OSM map still matches imagery from another source that is constant at all zoom levels and correctly registered to the world.

• I tried tracing a new building in Phoenix by using a GPS trace. The GPS trace was useless because of building echos. I had to wait until better imagery came along before I could trace the building.

• There are GPS failures that you need to be aware of just like you have to be aware of aerial imagery failures. The arm chair mapper page is a neglective fiction as it only point outs out the issues with aerial tracing.

• The TIGER data import had a bunch of lower quality data. The TIGER data was good enough to get census worker’s “boots on the ground” to count people for a census but not good enough for maps without correcting the TIGER data. However, I cannot imagine trying to walk around the US with a GPS to start the US map. Fixing the TIGER import with imagery and supplemental GPS traces was a good solution for the US.

• A mapper would have to buy professional grade GPS devices to have a better shot at accuracy. Even regular GPS mapping with consumer grade GPS devices is a great barrier to contributing to the map. However, in some cases that is all you have but it is good enough.

• I now have doubts about what ground truth really is. ;-) However, I am able to do useful things with the tools that I have available to me. LOL. I don’t need ESRI or CAD tools. JOSM and Potlatch tools have been great. Commercial and expensive close sourced tools will not provide any better results!

Greg

I came across Sun City West while out driving one day. It was a real intense effort to clean it up. First I had to align most of the TIGER imported roads before I could get to the landuse mapping. At first I did want to use a relationship for the golf courses. I mapped around this issue but it did not look right. It sounds like what you want to do. A golf course was created as the “larger polygon”. I then created two smaller polygons. I created the relationship with one outer and two inner polygons. I then whet back and traced both of the smaller polygons again to add the residential landuses. I did this because JOSM would complain about no tags on the inner polygons of a relationship. This produced the desired rendering that I was looking for but I was not as happy with the level of complexity that I left for additional mappers that may want to touch the area.

I hope this helps, Greg

It would be interesting to have a Summer building focus here in the US too as a way of morally supporting your prepartion for the Olymics. It will be interesting to see what you come up with.

I am sure that the armchair mapping is an issue with some mappers. As for me, I never really got the GPS thing going. In addition, the US Tiger import gave me a large amount of data to begin with that needed correcting. I understand the Yahoo ground truth verses, Bing ground truth and the big difference between the two at times. I am not sure how good GPS ground true is for some of the non-commercial devices available to mappers? All in all, armchair mapping is all that I have ever done because of the available Tiger import data as a starting point.

Now in addition to the armchair mapping, I go take pictures of areas that I am interested in. I have 3500 pictures on my cellphone. The pictures allow me to add additional information to the tracing effort. For example, walks along the light rail line have resulted in this area build up http://www.openstreetmap.org/?lat=33.469163&lon=-112.073748&zoom=18&layers=M. Chuckle: the fringe area around the Phoenix Zoo kind-of made it into a map of the week image. I traced all this area in from aerials and used pictures to remember information when I visted this area during a three day class http://www.openstreetmap.org/?lat=33.448403&lon=-111.957292&zoom=18&layers=M. I still have information on picutures that hasn’t been mapped yet.

It would be great to figure out how to bootstrap mapping events like you guys have in Europe.