Mapping a bench on site

Netbook + GPS receiver = on-site editor

Combine a simple netbook with a GPS receiver and what you get, is an OSM editor, where you can see and edit OSM, while you are on site. This article explains an adapted edit/upload cycle, suitable for this mapping approach.

Advantages over the Track-And-Note-Approach

Editing on-site makes mapping a lot easier, since you don't have to connect your GPS-track with your notes and memories afterwards. When you draw the map later, you cannot go back and resolve ambiguities you did not note down with sufficient precision (e.g. you took pictures of an intersection with five roads, but which is which?).

A netbook with GPS

• shows your position in JOSM
• logs your track
• enables you to compare OSM-data with the real world
• allows you to edit the map in OSM while you are on-site

Prerequisites

As you probably guessed by the title, you will need a GPS receiver and a netbook. As most configuration steps depend on your netbook, operating system and GPS receiver, I cannot cover them here, instead, I give a little overview.

Connect the GPS receiver with the netbook

You can either connect your GPS connector via USB or via bluetooth. Set up and test your connection, while you are still at home.

Install JOSM

java -Xmx1024M -jar ~/software/josm-tested.jar

On a linux system, you may want to write a little script to connect to your GPS device and wrap all the little parameters, so all you have to do on site, is type a single command.

Mapping/Edit cycle

Preparation

As with any other useful approach, you start with some preparations.

Common preparations

Before you go on any mapping trip, you plan where to go and what you expect to map. As always, it is a good idea to check what is already present in OSM and which unresolved issues exist within that area.

Prepare the area with satellite imagery

Optionally, you can pre-edit the area using areal imagery. The most useful features are clearly the roads, as they give you a basic structure for your mapping trip. Depending on your level of detail, this can save you from going down each and every road.

You can already draw clearly distinguishable features, such as roads, buildings, tennis grounds. Notice any unclear and unmapped features. When you go on site, you fill in the unknowns.

This preparation will not only save you time on-site, it gives you an orientation and a feeling for the area you are going to survey.

Prepare your netbook

After you have roughly selected your area, you download your data in JOSM (the Slippymap is handy here). Save the layer, so you can load it later; check, if the file is loadable.

Optionally, you can download satellite imagery using the WMS plugin.

• Eventually, zoom in on your map to get images with a higher resolution.
• Open a new WMS layer by clicking on WMS-> Yahoo Sat, this should load images for the current view.
• Zoom out, until you see the entire area, where you want to go mapping.
• Save the WMS layer to a file; check, if the file is loadable. You can use this layer in subsequent visits to that area.

Charge your netbook and your GPS device.

On Site

Netbook on site, running JOSM

Get your bearings

First, you should figure out, what's right and what's left. Turn on track recording from the LiveGPS plugin and walk a couple of steps along some road. This should give you a good idea of what road you're on.

Edit the map

When you're on site, you enter what you see into JOSM. Orientate yourself on the features already present. The presets in JOSM are useful here to fill in the data. When you come across a feature you want to map, but don't know the tag by heart, enter it as a FIXME, note suitable properties and correct the tag later.

Editing with JOSM in your hand is a two-way process. If a feature is present in OSM, check if it really is there (an intersection may have become be a round-about) and if it's properties are correct (e.g. if the street name is spelled correctly).

Hints

• While you draw, turn of "automatically center on your position", otherwise, the map may move underneath your cursor.
• Save your data layer often.
• If you're netbook has a mobile internet connection, you can look up features and tags, but watch your costs, when downloading large sets of images.

Post-processing

Yes, there usually still remains some work to do, when you are back online. As you already inserted all information in the editor, the post-processing is pretty simple.

• Of course, you want to upload your data.
• Resolve any conflicting changes
• Fix all the FIXMEs you created, while you were out there.

A word about the hardware

Netbooks in general

Although this approach is technically possible with any hardware, where JOSM runs on, a netbook is currently the best companion for an OSM mapper.

• lightwight
• you can hold them in one hand and type with the other (try this with a notebook, unless you are Arnold Schwarzenegger)
• runs software available for PC (esp. JOSM)
• cheap (mine is available for 150 Euro)
• and you can run navit using OpenStreetMaps for navigation

Recommendations

From my experience, there are some issues you should consider, when buying a netbook for mapping, mainly ergonomic ones:

• the display should be readable in bright sunlight
• the display should not show reflections, you want to see the editor, not yourself (so-called "glare-type-displays")
• touchpad should be precise (mine isn't, and I have to fumble around when drawing)
• time on battery (mine runs about 3 hours; plenty time to let my arms go numb)
• hard-disk vs. flash-memory: flash-memory is less sensitive, should you drop your netbook

I described my own hardware on my user profile.

See further

• Mapping techniques
• JOSM