#OSM Tracing Guide for Dar es Salaam, Tanzania
The Dar es Salaam area has experienced deadly flash floods in recent months, and the map data generated by this event will be used to develop an early warning system to alert residents of future flooding.
This tracing guide focuses on the most important features in the area: buildings and roads.
##Getting started
We have some fancy hi-res imagery from DigitalGlobe, for your tracing pleasure. iD editor should default to using this, but if your imagery looks blurry or hard to see, double-check that imagery is set to Custom
You can change the imagery like so:
You may also want to brighten the imagery to make it easier to see:
##Buildings and walls
###Understanding what's what.
We're interested in the following types of area:
- Buildings. These will look like "normal" structures, with roofs, walls, etc. These vary a lot - they may be constructed from metal, wood, or primitive materials.
- Buildings under construction. These will look like walls, but about the size of a building and with partitions for rooms. These could be dark (indicating that a foundation has been dug), lighter (indicating a filled-in foundation, maybe with short walls), or white with shadows (the walls are getting taller)
###Tracing buildings
To trace, select the Area tool (Shortcut: 3) and draw around the building/wall. Double-click to finish. The process looks like this:
Next, we classify (or "tag") the building, using the buttons on the left side of the screen:
If you don't see the "Building under construction" type, try searching for it in the search box:
Note that once you've traced a building, you can square the corners easily by hovering and clicking the icon (Shortcut: s)
##Roads
First we trace them, then we classify them. The whole process looks like this:
###Tracing roads
To trace a road, use the Line tool in iD Editor (Shortcut: 2) and trace along the middle of the road. See below for an example of too few nodes (left), too many nodes (center), and the right amount of nodes (right).
Make sure the roads connect to each other where they cross. You should see a node appear at each intersection (see below).
###Classifying roads
We're going to tag all the roads as unclassified because teams in the field will be tagging them later.
That's it! For more resources, see: