JOSM

Load all objects of a changeset

For certain tasks you need to have all objects contained in a changest. This may be the case when fixing things when an edit went wrong (e.g. some objects were tagged the wrong way).

Requires:

reverter plugin

How to do it:

open a new (empty) layer
History -> Revert Changeset
enter the changeset ID, select "revert fully"
load the changeset and all objects. JOSM will ask you to download objects which aren't contained in the current layer (which is empty), confirm this with ok.
wait until everything has finished
undo the revert operation by pressing ctrl-z (or using the button/menu)
update data to be sure that everything is up-to-date.
click upload to verify that there are "no changes to upload". If there are changes, look at the command stack/undo buffer.
if needed, purge unwanted objects

Drawing buildings

These guides are focused on doing the job the most efficient way using keyboard shortcuts and as few steps as possible.

Requirements for all techniques:

Basic knowledge of JOSM.
Basic knowledge about drawing from aerial imagery.

Terraced buildings with existing house number nodes

Initial situation: house numbers were mapped as single nodes and proper aerial imagery is available. In this case 0.05m/px aerial imagery provided by Aerowest were used.

Requires:

buildings_tools

How to do it:

Switch to "Draw Buildings" mode (press b). Take the little overlap of the roof into account and click the upper right corner to start the base line.
Finish the base line on the upper left corner. Now continue by drawing up the area, including the house number node. Take care to include a single node instead of multiple ones.
Click to complete the building. The node will be deleted, the building will be tagged building=yes and will inherit all tags and relation memberships of the node.
The next 3 steps are optional, especially useful for long rows of short buildings when it is difficult to get the orientation right on the first building. Doing this now will help a lot when buildings are offset from the center line. Switch to "Create areas" (press x). Extrude the area by ctrl-clicking the lower line to cover all connected buildings:
Now correct the rotation and position.
Use "Create areas" (x) to move the lower line back to its correct position. Switch back to "Draw buildings" (b)
Begin the next building by clicking the lower right node of the previous one, draw the base line to the opposite node.
Click on the node and draw up the building area.
Repeat steps 7+8 until all buildings are drawn.
Adjust single buildings if necessary, then select all connected buildings and move them to the correct position on the ground.
Finally fine-tune by aligning the buildings with e.g. fences, walls and hedges.

Round extensions

This describes how to create circular extensions of buildings like bays or stairwells.

Requires:

utilsplugin2

How to do it:

Draw the building. If the extension isn't on the same height as the roof and the imagery isn't perfectly orthogonal move it accordingly.
Draw a way from one corner of the extension to the outer edge and the other corner. You don't have to hit the center line, any point on the edge will do.
Press shift-c to create the arc.
Complete the way to form an area.
Add the building to the selection by shift-clicking it, then hit shift-j to join both. Continue mapping the building.