I have done most of my Open Street Map editing using the free JOSM Editor, as I feel it has a number of advantages over the default, Flash-based, Potlatch editor built into the website. The feature I use most is the various background image layers, but also being able to quickly loading my GPS tracks and support for other plugins are useful too.
JOSM Imagery Layers
When editing, primarily I’ll use Bing aerial imagery (also available in Potlatch) to help align my GPS tracks and photos. However, in areas where high resolution imagery is not available, I can switch to the Ordnance Survey Open Data Street View layerA nominally 1:10,000 series of maps, not to be confused with Google’s street-level photography.
There are also a number of older maps which are now out of copyright, and so features such as hills (which don’t change much) can be added to OSM. They can also be useful for checking routes of old railways etc., although the alignment can easily be 50-100m out. There is a list of old map sources on the OSM wiki — however, coverage is incomplete, and sometimes the servers are not available for whatever reason.
When editing in hilly region, I sometimes find the hill shading incorporated into the cycle map useful; and again, this can be loaded as a background layer (although it can also be a bit slow to load at times). Finally, I also occasionally load the OSM tiles as a background, which at first seems counterintuitive, but can be useful.
There is also support for displaying multiple layers at once, being able to alter the transparency of each. But this often becomes very confusing, as it is not always apparent which layer something is from.
JOSM can directly load GPX files, as well as (optionally) downloading other GPS tracks uploaded tot he OSMwebsite. I usually change the colour of my tracks, and set them as the top layer, so that they stand out against the other tracks and features.
I have installed quite a few of the available plugins for JOSM, but the two I find most useful are:
Buildings Tools which lets you quickly draw rectangular buildings. I have configured the preferences to automatically set
source="survey;bing" as this is usually the case. Complex buildings can be drawn in parts, and made into one using the
shift-J join shortcut. When combined with the feature to constrain the geometry to selected ways, this is especially useful.
Improve Way Accuracy lets you realign a series of nodes with fewer clicks—especially handy when using a trackpad. Simply select the way, press
K, and click to realign.
ctrl+click adds a new point, and
shift-click locks the movement of a specific node.
Having a much wider series of tagging presets built into the program speeds up editing IMO. Although the grouping of them sometimes seems counterintuitive, so I added the preset search dialogue button to my main toolbar.
I have also
developed a preset for source tagging based on another similar preset for Spain. See separate post on this
I’m sure there are loads of other useful plugins/presets etc. out there that I am not aware of, but these are the ones I have been using to date.