[Talk-us] Trimet updates to OSM in Portland, Oregon area - workflow

PJ Houser stephanie.jean.houser at gmail.com
Fri Mar 4 05:16:08 GMT 2011

Regarding the updates to OSM by 4 Trimet interns, in 4 counties around
Portland, Oregon...

Our updated workflow is still in testing, but we have found this to work,
albeit, slowly.

Using ArcMap 10, we are creating reference geodatabases in which to organize
and store our jurisdictional data.
- Includes most recent streets & trails data from RLIS for Washington,
Multnomah, Clark, and Clackamas County.
- Projected in WGS 1984 to match OSM's exported data.
- Attribute fields for streets and trails are deleted or edited to match OSM
tags. The attribute conversion maps are not yet finalized.

County datasets are created
- Streets & trails inside or within 1 km of the county boundary
- 10 foot buffers are created around streets and trails per county. Buffered
trails & streets are merged.

County data is converted to OSM format
- Using an ogr-to-osm Java-based script, we convert county streets and
trails to .osm
- In JOSM, several attribute fields have to be edited since ArcMap limits
field characters and several OSM tags have lengthy keys.

Download OSM data
- Nightly, we download West Coast data from Geofabrik.
- The data is broken up into the counties and sub-county portions (5 - 15M
sizes) by Osmosis. This allows quicker upload into ArcMap (5 - 10 min)

Create a "diff" file (difference) - includes only OSM highway lines that are
over 10 feet from jurisdictional data.
- In ArcMap 10, with OSM Editor extension, we load a sub-county area and
symbolize lines.
- Select by location all OSM highway lines that are within the 10 foot
buffered jurisdictional data. Invert selection, and export as our "diff"
- Convert to osm using ogr-to-osm script
- As errors are resolved, the problem features are deleted from the diff
file to track our process

Load files in JOSM, in order from top to bottom:
- area OSM data
- jurisdictional streets data
- jurisdictional trails data
- diff file
- gpx version of diff file (better control of symbology but unable to edit
- aerials

Edit in JOSM
- using bright symbology, the diff file highlights OSM data that needs to be
- we use aerials, OSM tags, and common sense to see if OSM or jurisdictional
data is correct.

If feature exists in OSM but is incorrect, either in tags, directionality,
or geometry:
- make sure to maintain OSM tags while adding jurisdictional tags
(copy/paste from OSM to jurisdictional, then copy/paste all tags from
jurisdictional to OSM)
- check geometry and alignment based on jurisdictional data and aerials
- Delete edited feature from Diff file

If feature doesn't exist in OSM:
- copy/paste feature from jurisdictional data to Area OSM layer.
- Merge node(s) as needed to connect the updated feature with the
surrounding features. Check against aerials.
- Delete edited feature from Diff layer.

If jurisdictional data is incorrect, we will track the local IDs of the
features and provide feedback to the jurisdiction who maintains the data.

PJ Houser
GIS intern, 503-962-5711 (office)
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