|Version 18 (modified by frawe, 4 years ago) (diff)|
Introduction to JOSM
A "node" is a point and a "way" is a line connecting multiple nodes, and a "relation" is an ordered sequence of ways. An "area" is a way whose ends are connected, but other than that isn't special. If a road or track or path is curved, it is approximated using a number of nodes within a way, and short lines connecting them. A way has a direction, which is useful for a number of tags, e.g. "oneway=yes" is a road which goes only in the direction the way is drawn. Other tags refer to being on the left and right; of the direction of travel along the way.
JOSM is a Java program, and comes in a .jar file. If you don't know how to start it, ask someone familiar with your platform how to run a Java program.
When JOSM starts up, it presents you with a few messages about recent changes in JOSM. You should have a look at this page from time to time as it keeps you informed on some of the more interesting changes.
Your next step should be to download some data. If you have a GPX file (downloaded from your GPS receiver) for the area of interest, load it into JOSM (File/Open). That will show you the area of the GPX file. Click on the green down arrow to fetch the data from openstreetmap.org.
An alternative is to download existing GPX points from the OSM server. In order to start this process you will need to know the latitude and longitude coordinates of the relevant area. The easiest way to do this is to use the download dialogues slippy map in the first tab. You can browse this map, zoom in and out and mark the area you're interested in. Read more on the download dialogue.
Editing in JOSM
The first step of actual editing is to add a node to the OSM data where there will be a junction or a significant change in direction. To add a node, highlight the node button, either by clicking the 2nd button in the left menu bar, or by hitting the "A" key on the keyboard (the 2nd button should then be highlighted). Move the mouse cursor over your GPS track, and left click it wherever you want a node to be. A white dot (a selected node) should appear and a rubberline span from that dot to the mouse cursor. As you create subsequent nodes the earlier nodes will be shown as red dots.
A series of joined nodes forms a way.
Ways on their own are not of much use unless they are tagged to say what they represent. Map Features shows all the current key value pairs which could be used on a way. Ensure the properties pane is open on the right hand side of JOSM, the 8th button on the left (an icon with a wrench over a document) should be highlighted, if not click the button or hit "Alt+Shift+P". That properties pane has three buttons: a plus sign with "add" next to it, then "edit", then "delete".
Editing properties refers to all the currently selected, i.e. highlighted, elements (nodes and ways). To select anything you must be in select mode which can be switched into by clicking the first of the left hand icons or hitting the "S" key. Ensure your new way is highlighted, then click the "add" button, a dialog box will appear and you will be asked to select a key and a value. Type in the key/value pair which represents the way you are creating, e.g. for the key type "highway" without the quotes, and for value type "secondary" again without the quotes. Now click OK. You have now tagged your way.
Uploading to OSM
JOSM now performs a quick check on the data you're about to upload. If it finds warnings or errors you'll be presented a list of them. Click "No" if you decide to fix these problems and try again afterwards. Otherwise click "Yes".
Finally JOSM will present you a list of changed or newly created elements for reviewing it. You're also asked to provide a short freetext summary of you're edits. This description will be saved with your data on the server and serves information purposes like for example the Recent Changes list.
With your final click on "submit changes" your data will be uploaded and visible for everyone else.
Please be careful with editing and uploading data. When in doubt if everything is ok, rather refrain from uploading and save the area locally on disk to check back to it later.
There is no simple answer to the question when and how often to upload. You neither should edit the whole day and then upload everything at one nor upload every minute after adding a way. The former to keep data in memory small, make uploads faster and minimize the risk of your edits colliding with someone else editing the same ways in the same area. The latter to minimize the overhead each upload poses on the server in means of CPU time and also database size since each change also means processing and saving some meta information.
If possible group your edits. In logical as well as in geographically units, this also makes it easier to give a good upload summary.
A couple of other points about creating ways.
1) Dual carriage ways should be drawn as two separate parallel ways, with each carriage way being a different way.
2) If a street is one way (including the individual carriageways of a dual carriageway) the way should be drawn in the direction of travel.
3) The key / value tagging is case sensitive, all keys should be entered in lower case.
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