Project Documentation

Summary:

The City of Sacramento provided the focus for the Area of Interest (AOI). Specifically, this AOI was Mid-Sacramento, which served as the initial observations, and subsequently partially supported the premise via quantitative data. This data originated from the Sacramento GIS Data Portal as PD Dispatch data 2015. The main premise was to correlate criminal incidents with distributive funds that may be available to individuals committing the crimes. The Dispatch data did not include any demographic information on these individuals, so the analysis continued with identifying the Hot Spot regions of crime within the city scope. Community demographics supplemented the Hexbins, used for hot spot aggregation, via Ersi’s resources. The obvious conclusion drawn is that economically stressed areas may attract external community influences as identified by the Hot Spot analysis. These identified areas are; Downtown, Alkali Flat, Midtown/Winn Park/Capital Avenue, Mansion Flats, Southern Pacific/Richards, and Boulevard Park. The Hot Spot analysis was provided with ArcGIS Pro by using the ‘Space Time Cube by Aggregation’ tool. This tool generated a higher granularity than the tool that is provided within ArcGIS Online.ArcGIS Pro and ArcGIS Online are not entirely compatible. Pro can handle large datasets, contingent on PC resources, and can provide charting analysis tools that are not equivalent with the Online experience. Two charts were used in the analysis within ArcGIS Pro: linear chart with a series from one or more fields, and Ordinary Least Squares. These two charts did not produce a counterpart within ArcGIS Online. The Online datasets require preprocessing steps to manage the dataset size for rendering and performance.

Purpose:

The study area for this Web GIS project will be the city of Sacramento. Specifically, the data will be confined to those regions that exhibit high incidents of crime. The purpose for this data restriction is to comply with the original project requirement; to keep the ERSI credits low, and to provide a smooth and fast online presentation. Consequently, this requirement will influence the actual conclusion for this project. However, the main objective for this inquiry will be purely academic – to explore the sufficient tools to portray an engaging, but narrowing story. The narrative for the project will be to compare the social distribution of governmental funds, within a temporal manner to a disadvantaged population of the city, and to correlate the availability of these funds with criminal behaviors that may ensue.

Description:

The two main data sources that were obtained from the City of Sacramento web site are the 2015 Dispatch data, and the city boundary. Other feature sets were found on ArcGIS Online. These data sources via ArcGIS include the following:

Neighborhood Police District Police Stations

This project is divided into three sections:1. Preprocessing to condense the Dispatch data2. Analysis using ArcGIS Pro3. Publishing to ArcGIS Online

Section 1

The original dispatch data consisted of 327,354 records with outliers extending from the city limits.

Data filtering was conducted with ArcGIS desktop version 10.5.1. The first process was grouped together within a workflow, via ModelBuider, for project documentation, and to have a tool for further usage. These tools consisted of changing the coordinate system from WGS 1984 to NAD 1983 stateplane California II FIPS 0402 feet, and excluding the outliers via a clipping process as shown in the following diagram.

Further data cleanup was accomplished using the Selection by Attribute query to eliminate dispatch calls relating to welfare checks, business checks, CSI, found property, incomplete calls, reporting assignments, stolen vehicle recovery, supplemental employment, tow follow-up, errands, alarms accidentally triggered, canceled or no evidence of crime, park check – to mention a few descriptive calls. This resulted with the overall record set of 178,234 rows as shown below.

A workflow was created to convert text time to a date datatype for subsequent analysis.

Section 2

The second process of this project was accomplished by using ArcGIS Pro version 2.0.1. This decision produced a means for various edits within an exploratory, ‘slice and dice’, approach prior to a commitment toward publishing on the ArcGIS web site, while perhaps utilizing fewer credits since processing was offloaded to a local PC machine. A workflow process was not established for this step of the project, since a new tool requires, at least, a semi-steep learning curve.The first step in the analysis was to use the ‘Create Space Time Cube By Aggregating Points’ on a monthly step interval and with a 1000 ft. distance interval. This process step yielded a Network Common Data Form (NetCDF), which is a machine independent data format used by ESRI within this software platform. This file can be viewed by using a view as follows: ‘Insert tab | New Map | New Scene’, and complete the inputs on the dialog box with the display theme option select to ‘Hot and cold spot trends’. This does not produce anything interesting – yet. The net step utilized is the ‘Emerging Hot Stop Analysis’ tool on the monthly query which produced the graphic as shown.

This graphic portrays the higher incident of crime concentration for the mid-portion of Sacramento – not too surprising since this is within my area of personal observations. This step produced the next graphic that also shows the aggregation containers as hex polygons that will be used in the following step. The aggregating prior step was enhanced by incorporating the ‘Enrich Layer’ tool to add ESRI statistical data that can further the analysis. The following graphic shows the enhancement – not visually very exciting!

The Enrich Layer was selected with the following columns and values. (Note: This geoprocessing tool levies credits):

HasData - Value of 1 means a hexagon bin had data for at least one of the selected attributes.MEDHINC_CY - 2017 Median household income value per hexagon bin.MEDVAL_CY - Median home value per hexagon bin.NLCDfrstPt - Percentage of land within each hexagon bin that is classified as forest land by the National Land Cover database.PCI_CY - 2017 Per Capita Income.RELSNAP - Food stamp recipients.TOTPOP10 - 2010 Population count per hexagon bin. A bin may have a population of 0 because it is in an industrial area or in a park.VACANT_CY - 2017 Vacant Housing Units.

The focus of this study was selected by identifying the police beats that are within the mid-city area using select by attribute process, and then using the Copy Rows tool to yield a new layer. This new focus region produced 41,850 records

This data subset was subjected to the similar analysis as outline above to focus only on this region, such as:

1. Create Space Time Cube by aggregation.2. Emerging Hot Spot Analysis.3. Enrich layer.

The following figure depicts the new hot spots for this continuing focus:

Using an Ordinary Least Square(OLS) regression did produce a correlation within the enriched layer with Per Income Capita (PCI) and location. PCI is a measure of the amount of money earned per person within a certain area. The scatter plot below, from the hot spot enriched data, shows a relationship of R2=0.39 within the mid-section of the city.

The next slide shows the hot spots relative the neighborhoods:

The following map shows the hot spots relative to the police districts and stations.

Section 3

The last major step for this project was to publish the content to ArcGIS Online. This task was accomplished by invoking the Share tab in ArcGIS Pro and selecting the Publish Web layer within the Share As grouping. The following layers were published from ArcGIS Pro to ArcGIS Online:

1. Sacramento_Dispatch_Data_AOI_PCS2. Sacramento_Dispatch_2015_hot_spots_Month3. Sacramento_Dispatch_Data_AOI_24. Sacramento_Dispatch_Data_AOI_2_hotspot_core_emerging5. Sacramento_Dispatch_Data_AOI_2_hotspot_core_emerging_enriche

d_OLS

The above layers were the only objects that were published. However, the online site captured the whole project – including the symbology! The layer titles that appeared in the contents pane, within the online site, were all prefixed with name(s) associated with the project on ArcGIS Pro. It was a messy cleanup.A miscellaneous step was included to compare the hot spot analysis from the space time cube/emerging tools within ArcGIS Pro, with the hot spot analysis provided ArcGIS Online. The credit usage was 178 to perform this online analysis. The following graphic shows this hot spot comparison:

The web map was shared via the Web App, to the ‘Geog 385 Web GIS’ group. The map link is provided below within the Reference section. The App was created by using the Web AppBuilder. The following widgets were added to enhance the end-user experience:

Bookmarks to provide extent reference for a return marker.

Charts offer analysis results.

Query delivers a visual via a selectable filter.

Discussion:

Working with ArcGIS Pro provides many new tools, enhancements, and an interface that is easy to use. The moderate learning curve was minimized though continual accessing ArcGIS online resources and applying the tool(s) to determine if the set of tools were applicable for this project. The overall usage experience was very intuitive as compared to using the desktop platform. The analysis was further enhanced through the charting capability within ArcGIS Pro. In contrast, the charting tools within ArcGIS Online are not currently compatible in functionality. For instance, ArcGIS Pro offers a linear charting method with the option to select a series from one or more fields as shown below:Another chart that was not accomplished Online was the Ordinary Least

Square (OLS) chart. The first diagram shows the OLS produced by ArcGIS Pro, the subsequent chart shows the results from Online:

These two charting methods are substantial in portraying an analytical story utilizing the Online approach. The granularity that is provided between the hot spot analysis is also significantly different in ArcGIS Pro and ArcGIS Online. This comparison was previously shown above. Perhaps the Online tool can be used as an initial tiered analysis prior to commitment of a project! The ‘Space Time Cube’ tool does achieve additional focus and detail, thereby narrowing the scope for the area of interest. Not shown here, but further refinement can be accomplished by using API to integrate with ArcGIS Pro – for instance by using the R environment.For the moment the Online experience appears to be limited to smaller datasets as compared to ArcGIS Pro. So, the need to filter large datasets is crucial for posting and sharing data to Portal, to streamline performance, and process a web story with reasonable user expectations. An enduring learning lesson from this project is to have all files organized and consistent by storage location and naming convention. This is not

always an easy accomplishment while processing data on the fly!

References:

ArcGIS Online:http://www.arcgis.com/home/search.html?q=sacramento%20police&t=content&start=1&sortOrder=desc&sortField=relevance

ArcGIS Map Link:https://arc-gis.maps.arcgis.com/apps/webappviewer/index.html?id=6ca6a6cef46d47a88beff024beff44c1

City of Sacramento:http://data.cityofsacramento.org/datasets/sacramento-dispatch-data-from-two-years-ago?geometry=-122.185%2C38.394%2C-120.803%2C38.77

http://www.cityofsacramento.org/GIS/Data

NetCDF:https://www.unidata.ucar.edu/software/netcdf/