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DATA COLLECTION
Two researchers collected data over two days in New York City (November 2007) and Los Angeles and San Francisco (December 2008). The first day was spent in the city's officially designated Financial District, the second in the Civic Center neighborhood.
1. PREPARATION
We obtained buildings, parcels and streets GIS data from the New York State Geographic Information Clearinghouse and the San Francisco Enterprise GIS program. Our team produced the Los Angeles building layer using a base map provided by the USC Geography Department.
We purchased two Apple iPhone 3G devices to use in these downtown settings because they utilize both satellites and cellular towers to obtain a geolocation. The advantage of using GPS enabled cell phones is that this technology obtains accurate readings under overhangs or inside buildings, while the conventional GPS units depend on substantial 'open air' to obtain accurate readings from satellites.
We pre-installed the software application XifPix on each iPhone. Once a potential security zone was identified, the field researcher used the XifPix application to take geotagged photographs of the security zone. The geotagged photos were used to delimit the boundaries of the security zones and the photos were included as a part of the security zone description in the project website.
2. FIELD DATA COLLECTION
Specifically, our researchers undertook the following operations:
Figure 1: Web interface for security zone assessment software
*One iPhone used the software to score each security zone on the three assessment criteria (Figure 1).
Figure 2: Polygons built by software from nodes collected in the field
*The second iPhone used the XifPix application to collect waypoints, or 'nodes'; the nodes were transformed into security zone polygons using our software (Figure 2). The security zone assessment software also allowed the researchers to assign a unique id, attach a description to each node, and immediately upload each node/photo to Picasa™ Web Albums.
*When appropriate, researchers further documented particular zones by taking several high-resolution photos or videos with a Canon PowerShot SD 1100 IS digital camera.
3. QUALITY ASSURANCE/QUALITY CONTROL (QA/QC)
We used Picasa Web Albums™ to check the photos/nodes for accuracy. Once all photos were adjusted and confirmed for accuracy, our software uploads all information (nodes, photos, and zone assessments) to populate the maps housed in the project website. These GIS maps can be found by clicking on NY, LA or SF links on the map to the left.