Page 1

Why NOT Google? (County GIS versus Google) Laurie J. Kurilla County Geographic Information Officer/Deputy CIO

Dis c lai m er This is not a Google “bashing”

This is a discussion about Data

This is a discussion about “business” uses of the Data


WANTED: Good Data (Bad Data Need Not Apply) Property tax assessments  Census information  Crime scene  Tracking pandemic cases  Impact of pesticide use  Responding to a variety of citizen questions, issues, and needs 

1 Rule of Data st

“The first rule when it comes to information found on the Web (and many other places as well): be skeptical. You would not buy a stock, write a check or believe a contentious statement from an unknown source off line -so bring the same challenging attitude to information found on line”. NY Times March 4, 1999

RECOMMENDATION: “Know the source”

The “Source” isn’t Google

Issues with Google Data 1.

Where’s the metadata? Source information  Date or origin  Data Integrity 

    

Positional Accuracy (degree of closeness of measurements of a quantity to its actual (true) value). Precision (reproducibility or repeatability) Completeness Quality Consistency

Projection and datum

(for spatial data)

Issues with Google Data 2.

Who’s the source?

Business data should be acquired from the original source

Every one (department/agency) in the organization should use the same source for the same data

LAPD Crime Maps uses Google L.A. Times

“Highest crime rate in L.A. ? No, just an LAPD map glitch” April 5, 2009

By Ben Welsh and Doug Smith

For 3 years, LAPD incorrectly mapped crimes (1,380 crimes per six months) at wrong location and made it visible to the public. LAPD considers their mapping system a “crime fighting tool”

Of more serious concern is the danger of spreading the bad data to other databases and systems. They had 4 million to 7 million page views/month!

County GIS Test 76 data points across Ventura County  Urban, suburban, and rural  Ground-truthed  Geocoded with 

County GIS Master Address Database  County Centerline  Google  Microsoft (formerly Virtual Earth) 

Geocoding Results Microsoft

is not worth considering

2 (3%) located on the structure 13 (17%) on the parcel 5 (7%) could not be located

56 (73%) were placed 10’ to 2000’ from the actual location !

Geocoding Results


Google: 49 (64%) placed on structure. 8 (11%) placed on correct parcel, 7 ( 9%) could not be located*

12 (16%) 10’ to 6000’ from correct location * These were “new” site development as old as January 2008. Google didn’t even have the streetnames. Many street names were incorrect in Google maps.

Geocoding Results


County GIS (w/ new Master Address Database): 66 (87%) placed on structure 8 (11%) placed on correct parcel 1 ( 1%) placed on centerline 1 ( 1%) could not be located, without falling back on Centerline as source.

Geocoding SUMMARY Master Address Database alone provides superior results to Google Cascading to Street Centerline when MAD doesn’t match, resulting in 99% match rate

A Picture is Worth ‌

A Comparison between Google &County GIS for 4030 Adolfo Dr. Camarillo, Google 8/12/09 NOTE: Google point is over 1 mile from actual location. (6000’) New development data (situs, and parcel) available to County since October 19, 2008! (Using ArcMap ) (note: as of 4/12/10, Google now maps it correctly)

Google view showing results for 4030 Adolfo Dr. Camarillo, CA

Google 8/12/09. location. (6000’)

Google point is over 1 mile from actual

4/12/2010 Update: Google now has correct location.

A Comparison between Google and County GIS for 3766 Dunkirk Dr. Oxnard, CA (4/12/10 update: Still not current imagery still ½ mile off, and still missing streets.)

1/2Mile from correct site GOOGLE This new development data has been available in the County data since January 2008.

Notice OLD imagery

County GIS

4/12/10 Update: “2010” imagery, still ½ mile off. Still missing the construction , so it can’t be 2010 imagery as misleading print at bottom of Google image might indicate.

A Comparison between Google and County GIS for 11657 Ellice St. Malibu, CA Correct Location


Inc o

rrec t

Str eet Na m


Incorrect Googled Location 1500’ off

Closing Thought: Source Matters The LAPD issue illustrates the pitfalls of blurring the lines between professionalgrade systems/processes and consumeroriented tools ď Ź It also underscores the importance of having experienced, professional GIS architects and analysts on your side when specifying and contracting the development of a complex mapping and data system. ď Ź

Your Challenge Determine the source Acquire data from original source Review the metadata Demand excellence (quality, precision, and accuracy)

Why Not Google?  

Data integrity.

Why Not Google?  

Data integrity.