OpenStreetMap

Marc Henshw's Diary

Discussion

Comment from Peter Dobratz on 13 February 2012 at 17:02

It's great to hear about another new mapper. I'm originally from Pittsburgh, so it's nice to see people like yourself updating the map in Pennsylvania. Let me know if you have any questions about editing the map.

Comment from Marc Henshw on 13 February 2012 at 17:31

Peter,

Thanks for offering some help! I do have a couple of questions. One is, the streets do not align with the satellite imagery. Should I correct for this? Another is, I noticed some places have the building outlined and labeled but also have a tag within them. Is this proper? Thanks for any info you can give,

Marc

Comment from Peter Dobratz on 13 February 2012 at 20:28

Marc,

The starting point for the map is typically a collection of data that has been imported from various sources. The roads came from the 2005 TIGER road data (provided in public domain from US Census Bureau). They certainly may be quite a bit off from reality. I've found that the Bing images are generally pretty well aligned, but it's helpful to confirm against GPS traces. There may be some that have been uploaded, or you can make and upload your own. Once you've confirmed the alignment of a few roads against GPS and satellite images, you can just use the images to update the roads. For more information about turning GPS traces on in Potlatch 2 (the default editor in your web browser), see:

http://wiki.openstreetmap.org/wiki/Potlatch_2/Primer

Note that there was a separate import of features from GNIS in 2009 and these are all single Nodes of POIs like churches, schools, and various public buildings. In many cases these are out of date and should be deleted. Also, they may be quite far off from their actual location.

As far as mapping POIs, some people choose to put single Nodes on the map, and others choose to use Ways to trace outlines of buildings. I prefer to map building outlines as I think it makes a better map. If you have a building with only one POI inside, then you just want tags on the Way for the building. If there's a node inside, you can copy the tags, and then delete the node.

Some buildings may have multiple POIs in them (shopping centers, etc). One method is to make a Way for the building and then put Nodes at the entrance of each shop. Here's a shopping center in Derry, NH that uses this method:

http://osm.org/go/ZfMgKuOK9-

Another method is to make separate Ways for each store in the building (this gets a little tricky since you have partially overlapping Ways). Here's a shopping center in Londonderry, NH that uses this method:

http://osm.org/go/ZfJ1ZihB8--

Also, note that when people have imported things for the entire US, they include a bunch of tags on elements that happened to be in the source data. These have little relevance to OSM and should probably be deleted (tags starting with tiger, gnis, etc).

Comment from Marc Henshw on 14 February 2012 at 21:16

Peter,

Thanks for the detailed info. Unfortunately, I don't live in the area anymore. I recently moved to Washington DC. No one edited the Brownsville region, so I thought I'd take a look. I think I'm going to stick with editing POI and putting in buildings. I see many road errors, but the aerial photography even when adjusted just doesn't line up right. It may be a while before I get up there to do any GPS traces. I appreciate you bringing me up to speed with your email, I understand the process much better!

Marc

Comment from GEOMSG on 15 February 2012 at 15:19

@Peter Thank you for the examples of shopping centers, I only started contributing today. The geocaching website changed from using google maps to OSM maps, because google was going to start charging groundspeak, they report that geocaching has over 2 million hits a day on google. So they moved to OSM. I love these maps! Maps I can contribute too?!?! so awesome. Thanks for those tips I really like how those shopping centers are done. Will be working in my small town.

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