San Diego geocoded SWITRS data

As part of our ongoing work to test and improve our geocoding processes, we recently looked at SWITRS collision data for the City of San Diego. In my past work when attempting to geocode data for San Diego, we found the various street networks were quite outdated compared to other areas in California. I presumed it was due to rapid population growth but a quick Google search surprisingly showed that might not have necessarily been the case: http://www.sandiegouniontribune.com/news/2011/mar/08/san-diego-growth-last-decade-is-the-slowest-ever/ Regardless of the reasons, it was difficult to geocode collisions since there were many new streets in the suburban areas.  In order to […]

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Geocoding collisions with invalid offset directions

Today’s blog is the final post in our geocoding overview series and addresses the scenario where a collision cannot be offset from the intersection due to an invalid offset direction. Although this situation can occur at any intersection, it is more likely to occur along longer roads such as state highways where small segments vary from the general orientation of the route. A great example is the Pacific Coast Highway (California state route 1) in Los Angeles. The Pacific Coast Highway is typically oriented north/south, but in some locations it becomes east/west or slightly opposite. This can create a mismatch with the offset direction in the […]

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Geocoding collisions at non-existent street network locations

In continuation of our geocoding overview series, today’s post describes the scenario where a collision cannot be geocoded because the location does not exist in the available street network data. The location may not exist for several reasons: The street network is outdated so it does not contain new developments The street network is incorrect and the roads appear in a slightly different location The collision occurs at a driveway, alley or other private entrance that is not a public roadway Typically the last situation is the most detrimental since those locations frequently have the highest number of collisions due to […]

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Geocoding collisions at offset intersections

Today’s blog post tackles the first geocoding issue outlined in our geocoding overview series: how to handle geocoding collisions at offset intersections. In the example below Collins St intersects with Reseda Blvd in two separate locations about 150 feet from each other: Offset intersections can be a common occurrence in some cities or they may just be isolated to several corridors. Regardless of their frequency, they pose a challenge when attempting to geocode collisions and in many cases can leave some level of ambiguity in the location. This is especially true if one does not have access to the original crash report to investigate […]

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City of Los Angeles geocoded SWITRS data free download

UPDATE Geocoded SWITRS data is now provided through the City of Los Angeles Geohub. You can search for SWITRS to find the latest available data at: http://geohub.lacity.org/datasets?q=switrs The data originally linked on this blog post below is no longer updated. ————–   On the heels of releasing the HSIP Helper a few weeks ago, we are now providing a full set of geocoded SWITRS data for the City of Los Angeles to planners, engineers, researchers, or anyone working with collision data in Los Angeles. While many of you have utilized the great service provided through TIMS at UC Berkeley, you may have […]

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Geocoding collision data for RoadSafe GIS

Accurately geocoding collision data is necessary when building a collision database that will be used for spatial analyses. Geocoding is the process of assigning a latitude/longitude (X/Y) coordinate to a descriptive location. For collision data, the descriptive location is typically a primary road and a secondary intersecting road. To geocode a collision the primary and secondary road must match to a location on a digital street network. When the collision location is described perfectly without typos, it is usually easy to match.  However, there are frequently typos, abbreviations or other anomalies that make it difficult to match the collision to a street network. In addition, […]

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