User:Ceyockey/source draft

Source refers to where information came from for data added to OpenStreetMap. Source information is fundamental to the verifiability of OSM content ... just as it is when used to support scholarly publications, Wikipedia pages, book content, and many other types of reliable content.

There is no consensus (as of January 2013) about whether source should be added at the object (node, way, area, relation) or changeset level. The running consensus is that source information is valuable.

Source on object versus changeset

There have been a number of discussions on this topic, the most recent of which appearing on the tagging email list in January 2013.

When adding source at the object level, an editor needs to consider what information about an object comes from what source. Consider aerial image tracing. If one traces a building from the imagery, then the tags added might be the following:

Tag	Value
building	yes
source	bing
source:date	2011-10

More details about the source can be added using the source_ref tag.

"source" can also be used as a namespace prefix to specify the source of a single attribute. For example, to attribute a source for a name tag, use source:name=photograph, or to indicate the reason for speedlimits (sign, roadmarkings, implicit speedlimits) use source:maxspeed=*.

If the tag already has a namespace prefix (e.g., mf:name=Broadway then use mf.source:name=photograph).

Use of the image tag implies source=photograph. It is not necessary to add a source tag in this case if this is the only source of information for the object. See also Geotagging Source Photos.

If a particular source is later found to infringe copyright (e.g., some source that was believed to be OK is later discovered or ruled to be copyrighted) then it would be possible to easily remove all OSM data originating from that source.

History

In a time when changesets didn't yet exist, the source tag was always added to objects; if you traced 1000 houses from aerial imagery, each house would carry an appropriate source tag. Since the advent of changesets, mappers usually prefer adding a source tag to the changeset as a whole because it is less work and adds less (unnecessary) data to the database. Adding source tags to individual objects is not deprecated however, and might still be required if different sources are used in the same changeset.

Reliability

The usefulness of the source tag is reduced in areas where data from many sources has been added. After many diverse edits the data may depend on so many sources that it can not be accurately attributed. Also, most mappers fail to update the source tag when they edit objects, leaving the source tag reflecting only the original source of the object. This is another reason why source tags on changesets are usually preferred; the edit history of an object can then be used to see the source tags of all changesets that have contributed to the current state of the object.

Annotations

Providing further information about tag values for other mappers and in some cases also for users. See the page titled Annotations for an introduction on its usage.

LOADING TAG LIST...

This table is a wiki template with a default description in English. Editable here.

JOSM annotation presets

 <item name="Data Source">
   <label text="Way/Segment/Node Data Source"/>
   <combo key="source" 
          text="Source"
          values="landsat,photograph,local knowledge,common knowledge,dictaphone,extrapolation,<other - please specify>"/>
 </item>
 <item name="Street Name Source">
   <label text="Street Name Source"/>
   <combo key="source:name" 
          text="Source" 
          values="photograph,local knowledge,common knowledge,dictaphone,<other - please specify>"/>
 </item>
 <item name="Road Number Source">
   <label text="Road Number Source"/>
   <combo key="source:ref" 
          text="Source"
          values="photograph,local knowledge,common knowledge,dictaphone,<other - please specify>"/>
 </item>

Most common sources and their meaning

This section lists the most commonly used values of the source key and describes its meaning. If there are more versions (by year, capitalization etc.) it is included once only. Most of the fields are blank, fill in what you know.

TODO: merge with Meanings for source tag values

Value	Country(ies)	Meaning	Website	Note
cadastre-dgi-fr	fr	WikiProject France/Cadastre French catastre maps. Mostly landuse
3dShapes	NL	3dShapes landuse and building shapes in The Netherlands and a bit across the border
PGS	wordwide	Prototype Global Shoreline. Low detail coastline generated from landsat imagery.
YahooJapan/ALPSMAP
KSJ2
bing	worldwide	Tracing of Microsoft's map service Bing aerial imagery
NRCan-CanVec-7.0
NHD	U.S.	National Hydrography Dataset. Imported rivers/lakes
cuzk:km	cz	Manual or semi-automatic tracing of Czech catastral map	http://www.cuzk.cz
OSAK	Denmark	Imported address data from official Danish source
kapor2
survey	worldwide	see above
SanGIS␣Addresses␣Public␣Domain	San Diego U.S.	SanGIS government data
Geobase_Import	worldwide	Geobase data. Mostly place names
HELP␣SERVICE␣-␣REMOTE␣SENSING...	cz	Import source of some parts of road network in the Czech Republic	http://www.bnhelp.cz
dibavod	cz	Import source of water bodies in the Czech Republic
uhul:ortofoto	cz	Usually manual tracing of grey-scale aerial imagery by Czech office for economic use of forests
IBGE	br	IBGE Import. Brazilian federal data

Imports

Many bulk imports have their own unique source tag. Users doing imports are advised to give notice of their intended actions on the Import Mailing List.

Special source tags

• source=AND Data donated in 2007 by AND Automotive Navigation Data, see the AND Data wiki page.
• source=DOP_LVA
  • source=DOP_LVA_BY_01 - (pilot scheme from 2008-12-12 to 2009-03-31) extending OSM by digital orthophotos provided by the land surveying office of Bavaria, Germany

When tracing from aerial or satellite imagery, the imagery provider is often given as the source, e.g. Yahoo, Bing, Landsat, etc.

Source tags used by 'bots

• Source=PGS - Almien coastlines (PGS)
• Source=GSHHS - Almien coastlines (GSHHS) (not used much)
• Source=waypoint - Waypoint upload tool [1]