Introduction to JOSM

JOSM Terminology

Node

A node is a point.

Way

A way is a line connecting multiple nodes. Way, therefore, is a general term for series of joined nodes, not just for roads or ways in reality.

Relation

A relation is an ordered sequence of ways and nodes, a logical container used to group elements.

Area

An area is a way whose ends are connected.

Tag

Tags describe what each node or way represents. Tags are organized into "keys" and "values." Keys are basically larger categories, such as "Highway" or "Land Use," while values are specific features, such as "Primary Road" or "Residential Street," and "Residential" or "Retail" land use.

If a road or track or path is curved, the curve is approximated using a number of nodes within a way, and short lines connecting them. If a way has a direction, that is indicated partly by using tags. For example, "oneway=yes" is a road that goes only in one direction. Other tags refer to being on the left and right of the direction of way along the way.

Start a JOSM

JOSM is a Java program, can be run from main page.

Your first edit with JOSM

Welcome screen

When JOSM starts, 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.

Downloading

The next step is to download some data. You can practice using JOSM by downloading your neighbourhood or locality you know or just recently visited.

OSM data

Next, add data for that area from main server, click at: Download from OSM (Ctrl+Shift+↓).

"Slippy Map" tab will be displayed, a map of the world. But you need to select smaller area for your edit, not entire globe (thus you will see "Download are too large" message).

To move around the map and select the specific area you want to download, there are several tools:

• Click with the right mouse button to drag the map
• Use the scroll wheel to zoom in and out
• click with the left mouse button to define an area.

After "Download are too large" error disappeared and you selected a region, click "Download" to fetch the data from main server.

Enable Aerial imagery

For most places on earth, there at least one imagery available. You can pick one from Imagery menu at the top of the editor. While Bing and Mapbox are popular, but there may be more recent resources for your locality.

Bing and Mapbox may have different levels of detail and clarity in different places, so often worth checking both. Simply select one of them from the imagery menu and you're ready to go.

Mapbox-only: you can ​request a better imagery for region of your interest (​announcement in 2014-04-11 by Eric Gundersen)

When using imagery, keep in mind that imagery may be offset. That is, due to complexities in processing satellite imagery, features on imagery may not be at the same location as they are in the real world. For reference, check existing features in OpenStreetMap data and compare them with the imagery or download GPS tracks. To download GPS tracks from OpenStreetMap, check the "Raw GPS" box in the download dialog. If you observe an offset in the imagery, you can correct for it by selecting the "New offset" item in the "Imagery" menu.

Editing in JOSM

JOSM is an offline editor which means everything you do won't be visible for anyone else until uploading it to the server. This makes it possible to experiment and repeatedly moving, tagging, adding and deleting elements without breaking anything. Subsequent actions on a single element will go into the database as a single modification when uploaded.

Adding a Node or a Way

The first step of actual editing is to add a node or way to the OSM data. You can add standalone nodes or you can add nodes to ways, especially where there is a junction between two ways.

To add a node, highlight the "Node" button, either by clicking the 3rd button in the left menu bar , or by hitting the "A" key on the keyboard (the 2nd button should then be highlighted). Then, move the mouse cursor over where you want the node, over a way or over your GPS track (if you uploaded one) and left click wherever you want a node. A red dot (a selected node) should appear and a rubber-line span from that dot to the mouse cursor. If you create subsequent nodes, the earlier nodes will be shown as yellow dots.

A series of joined nodes forms a way.

Adding Tags

Ways or nodes on their own are not of much use unless they are tagged to say what they represent. The ​Map Features page shows some popular tags, this page will never complete about all tags.

The first step in adding tags is to be sure the Tags/Membership Dialog is open on the right hand side of JOSM. The button on the left should be highlighted. If it is not highlighted, click on it or hit Alt+Shift+P. You will see the Tags/Membership Dialog, which has three buttons: Add, Edit and Delete.

To edit the properties of a node or way (such as adding a tag) in the Tags/Membership Dialog, the way or node must be selected.

1. Enter Select mode by clicking on of the left-hand icons or hitting the S key.
2. Highlight the way or point you wish to select. Click the Add button.
3. A dialog box will appear, and you will be asked to select a key and a value for each tag. Type in the key/value pair that represents the tag you are creating. For example, for the key, you might type "highway," and for the value "secondary" (no quotes).
4. Click OK. You have now tagged your way. You can add several tags to one object.

Presets

Instead of adding tags manually you can also use Presets.

All presets can be found: 1. from main menu (shown on the left below) 2. main toolbar (no picture below). 3. F3 shortcut (pop-up menu shown below on the right)

Presets for currently selected object(s) are displayed above tags for current object (displayed in Tags/Memberships Dialog):

Left mouse click on respective preset heading will open complete preset view

Uploading to OSM

If you are happy with all that you have done then you must upload your work to the OSM server. Click on the green up arrow .

This will automatically trigger validation. Review all validation warnings and resolve all errors (Complete list of errors and how to fix them) before you upload. This will prevent unfortunate mistakes such as un-tagged objects or unconnected roads.

Before you upload, add a proper changeset comment and specify what source you used. This is important as it will show other users who see your changesets what this changeset was intended to modify and from where you took the information.

JOSM will give you an overview of the elements that it is about to upload. You will be asked to provide a short text summary and the source of your edits. This description will be saved with your data on the server and provides information, for example, for the ​Recent Changes list.

If you need more details or have questions about upload process, it is precisely covered at Upload to OSM page.

Thank you!

No matter if you pick JOSM as your main tool or as ​one of many editors, don't forget to use help page or simply press F1 over button or any interface element, because we had no time to cover all topics.

What next

Results of your job

• Will appear at ​openstreetmap.org "Standard" layer within few minutes
• Data in your routing software, maps and other services: will be updated per each service (from minutes to days, weeks and months)

Tell your friends

• How it is easy to update data, how your results get displayed quickly. Truck drivers, couriers, photographers, bikers, journalists, fisherman and simply runners with GPS are always welcome in OSM.
• Precise and actual information may affect how you make decisions in your life. The more people active in project - the faster data gets updated. And while ​a few contributors can be called as "active" at given point in time. Every small change advances OSM to complete and actual state
• OSM data may be viewed as clocks: without an arrow you wouldn't know minutes. it's often gets outdated - simply refresh it, when clock "stops" we wind up.
• OpenStreetMap is about whole planet in the same way how your clock about current time

External links

• ​Mapping with JOSM with animations, by Mapbox team, covers mostly the same topics
• ​Your first steps with JOSM - the Java OpenStreetMap editor 09/02/2016 by Ramya Ragupathy at Mapbox blog

See also

• Objects in OSM data model

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