Basemap

From Wazeopedia

(Redirected from User:Kartografer/Basemap)

Waze map editors use the term basemap to refer to roads imported from external sources that have never been edited and for areas that contain them.

Background

A basemap (or base map) is a collection of reference data intended to provide visual orientation to users of a map, so that further details can be added and displayed on it in a meaningful way. It may include data on imagery, topography, roads, political boundaries or other things, depending on the purpose of the map. In many countries, Waze has licensed and imported data on roads and other features from various sources to serve as its basemap, and this is the foundation upon which users and map editors build to create a usable navigation system.

Depending on the data source used to import roads for each particular country, basemap roads require various updates from map editors in order to provide efficient navigation and useful display. This can involve confirming directions, turns, and names, adjusting geometry and connectivity, removing extraneous nodes and segments and setting road types, locks, elevations and other road attributes. Because they require specific cleanup from editors, and because they contain unique features relative to roads created and edited by users, map editors often refer to these unedited roads and areas that contain them simply as basemap.

Basemap roads in the United States

Basemap.jpg

Waze imported TIGER data from the US Census Bureau to serve as its basemap in January, 2009. TIGER data provided somewhat accurate names, locations and cities/states for roads, but it did not include road directions, types, allowed turns, elevations, or any navigation history. Because this data was designed for location of people and places and not for navigation, it contained many odd angles and extraneous geometry and junction nodes when added to the Waze map.

The default road type for basemap roads is  Street , but during and subsequent to importation, Waze ran automatic processes to assign road types based on names and other features. For example, most if not all roads with "I-xx" names (Interstate Highways) were first assigned as the type now called  Major Highway , and later they were reassigned as  Freeway . Other roads with variants of "highway" or "route" in their names were assigned as the type now called  Minor Highway . Some roads were automatically assigned as  Private Road ,  Unpaved  or other types. None of these automatic road type changes were recorded as edits, so while most unedited basemap roads are  Streets , some of them have other types.

Basemap roads in the USA have unknown direction and soft restricted turns by default, but Waze is designed so that users add data to roads as they drive over them. When enough users drive over a road of unknown direction from node A to node B onto another segment, Waze will automatically set the direction to one way (A→B) and will set the turn from node B onto the other segment to soft enabled. If enough users drive from B to A on this same segment, Waze will then set the road to two way, but the turns will still be unconfirmed. These directions and turns remain guesses and are affected by various routing penalties until set by an editor. Once a segment is edited and its turns are confirmed, penalties no longer apply to enabled turns, and any restricted turns and forbidden directions become absolute and will not be routed.

Identification

Basemap2.jpg

Basemap areas are usually found where there are few GPS tracks. A lack of GPS tracks over roads could mean that there are not many Wazers driving there, that cellular data coverage is weak or even that the roads on the map are not drivable or do not exist. Whatever the reason, lack of GPS tracks is a good clue that unedited basemap roads are nearby, waiting to be edited.

It's easy to tell when the basemap roads were imported into an area, because most road segments will have the same creation date. If a road segment has that created date but does not have an updated date listed in its information, it is an unedited basemap road that needs to be updated. Additionally, features like unknown direction, unconfirmed turns, odd angles, excess nodes and segments that don't match imagery are clues that a road has not been edited much from its basemap state, even if it has been updated by someone.

Editing

The general information on Creating and editing road segments applies to editing basemap roads, but basemap roads have some unique features to look out for. Because of these features editors must be careful and thorough. Doing an incomplete job, such as only fixing geometry or deleting junction nodes, can turn a patch of roads from somewhat functional but clearly needing work to looking better but not working at all. This is because when a segment is edited, its direction is automatically confirmed, and when a turn is edited on the end node of a segment, the other turns from that node are automatically confirmed. Subsequent traffic cannot change confirmed (or "hard") turns and directions. More importantly, updated roads with one way direction will not be routed in the opposite direction, and any remaining hard disabled turns at a node, even if hidden by unknown or one way direction, will not be routed at all.

Here is a detailed procedure to follow when editing basemap roads:

  1. Delete unnecessary road segments. Some basemap roads represent driveways, walking trails, fences, waterways or nothing discernible at all. With few exceptions these should be removed from the map. Deleting these provides a more accurate map, better navigation and less work for editors.
  2. Adjust the connectivity. Oftentimes basemap roads will not connect where satellite imagery shows they should. They should be connected to provide proper routing. Any one-segment or two-segment loops should be fixed. Conversely, improper connections such as those off bridges and through barriers should be fixed too. Use the bridge tool to fix any bridges and disconnect any other roads where a junction is not passable.
  3. Delete unnecessary junction nodes. This allows Waze to use less resources when calculating routes and to give more accurate arrival times.
  4. Set the direction. If the direction of a road is unknown or one way, determine what direction the road should be and set it. Remember that once you edit a one-way segment, even if you don't change the direction, Waze will consider its direction confirmed and will not route traffic in the opposite direction.
  5. Set the turns. Hidden turns are revealed after the direction has been set. Confirm the turns; keyboard shortcuts such as Shift+Z to reveal restricted turns and Q+W on a node to allow all turns can help with this. Only allow U-turns where permitted by law.
  6. Confirm the name, city and state. Many roads are not within a city, particularly in rural areas, and some are not named either. Check the "none" box next to city and/or name in these cases. The road names page and approved sources can help determine names, and the local wiki for the area in which you are editing may give further guidance on how roads are assigned to cities. Even in the middle of one state, basemap roads may erroneously be listed in a different state. This should be corrected. Check local GIS or other approved sources for help in determining city limits and state lines.
  7. Adjust the geometry. Most basemap roads will have excess geometry nodes that should be removed to make the map easier to maintain. Most basemap roads will also not be aligned very well with satellite imagery. Where the imagery is accurate, they should be adjusted to match it. Geonodes should also be adjusted around intersections to provide proper turn instructions.
  8. Set the road type. Most basemap roads have the  Street  type, but the type may need to be changed to  Unpaved ,  Private Road  or something else. Satellite imagery can often determine whether a road is paved or not; see road types for more information.
  9. Set the elevation. The default is ground, but bridges and tunnels should have negative or positive elevations. If the bridge tool was used, make sure that elevations are not unnecessarily high.
  10. Set other road attributes. If a road has not been edited by anyone in Waze, it is unlikely that Google has street view to show speed limit signs, but it's good to check. Sometimes default speed limits can be added based on applicable laws. Depending on road type, a lock may also be warranted.

Basemap editing can be done well without user scripts, but for those who choose to use them, WME Toolbox, WME Validator and WME Color Highlights are particularly helpful in pointing out potential problems in basemap.