Palo Alto, California/Buildings Import

Goals

Import Palo Alto, CA has released a number of data set via its Open GIS Data initiative, one being a building outline dataset.

Schedule

John Novak leads the import. Cleanup and final address point conflation is now in progress.

Import Data

Background

Data source site: https://googledrive.com/host/0B5Urq1jZb1MYWWY4cnVaejNDLTg/paloalto/opengisdata
Data license: http://www.cityofpaloalto.org/gov/depts/it/open_data/terms_of_use.asp
Type of license (if applicable):
ODbL Compliance verified: Unknown

OSM Data Files

The generated OSM files can be found at https://github.com/oldtopos/PaloAltoCA

Import Type

This is an initial import of building and address city data. If the city releases substantial future updates, additional imports may be undertaken, presumably with manual conflation to preserve user edits.

Methodology is manual conflation via a JOSM layer (created from the CPA building outline and address files) with current OSM data downloaded into a separate JOSM layer.

Data Preparation

Tagging Plans

• building: yes
• paloalto_ca:id: int
• addr:housenumber
• addr:street
• addr:city

Address points that cannot be associated with a building polygon are imported as point features (nodes)

• addr:housenumber
• addr:street
• addr:city

Changeset Tags

• Changeset Description: Palo Alto Building Outlines and Addresses import
• Source: City of Palo Alto CA 0713

Data Transformation

1. Load building CSV file into PostGIS, convert kml column to geometry
2. Load address CSV file into PostGIS, convert kml column to geometry
3. Join address points to building polygons
4. Extract PostGIS building table data, to shapefile via ogr2ogr, filtering for only polygonal geometries, including gid column named as paloalto_ca:id. Join address points to buildings where proper containment exists.
5. Extract PostGIS address table data, to shapefile via ogr2ogr, filtering for address points not associated with a building.
6. Convert both shapefiles to .osm file using ogr2osm

Data Transformation Results

The generated OSM files can be found at https://github.com/oldtopos/PaloAltoCA. Note that this is raw output from ogr2osm. Manual merging and cleanup of overlaps is executed in JOSM before uploading to OSM.

Data Merge Workflow

Team Approach

John Novak is importing the OSM file geometry manually.

Workflow

1. Open buildings.osm in JOSM (Building polys with addresses)
2. Open paaddressnobuilding.osm in JOSM (Address points not associated with a building poly)
3. Select a block or set of blocks to be updated
4. Download the corresponding area from the OSM servers as a new layer
5. Select building outlines via JOSM search tool
6. Use manual inspection to look for features that overlap.
   • Toggle the OSM layer visibility to help spot overlaps.
   • Pay special attention to nodes that have building tags and existing schools (since they are frequently already mapped).
   • Make sure to delete buildings from the Palo Alto data when tags are copied from the import data to existing OSM data.
   • Copy selected outlines from buildings.osm layer and paste into downloaded OSM layer.
   • Merge address points not associated with buildings and manually merge to building polygons as appropriate.
   • Address points for commercial/retail and those that are not definitely associated with a building are left as address nodes
7. Commit the buildings into their own changeset.
8. Return to step 1.

Conflation

Since the OSM data is being hand-imported in manageable chunks, conflation with existing is handled manually in JOSM. I prefer existing OSM data and tags over the imported data. Existing address tags are merged with newly created building outlines.

QA

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