Create Graduated Symbol and Density Maps from Geocoded data Using ArcGIS Pro

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Introduction

This document aims to show how to carry out simple GIS Analysis using ArcGIS Pro (Vers 1.1.1)

Aim

The overall aim of the processes is to create a Graduated Symbol map and a Density map. This process will demonstrate Geocoding postcodes and then performing analysis using spatial joins and creating map outputs.

Required Datasets

A shapefile of boundaries of Wards downloaded from Digimap Ordnance Survey Data Download.
Code-Point Open data for Edinburgh downloaded from Digimap Ordnance Survey Data Download to give a list of all postcode units with centroids in Edinburgh.
Census population information for each postcode unit. We will use Geoconvert (http://geoconvert.mimas.ac.uk/index.html) to get Census population data for postcodes using the code-point postcodes as input.
A background OS map.

Summary of Processes

Step	Process Description	ArcGIS Pro Tools
1	Create an Address Locator to Geocode postcodes using Code-Point Open data.	Create Address Locator using Geocoding Tools Toolbox
2	Geocode addresses	Geocode input source (postcode) data as CSV.
3	Clip points to spatial boundary	Select By Location within Ward boundaries. Invert spatial relationship before query to delete all those features outside the area.
4	Calculate populations within boundaries	Do a One to One Spatial Join and Sum the attributes for population total attributes for population
5	Classification and Symbology	Display using classified graduated symbol or colours
6	Create Density Map	Use Point Density Toolbox on geocoded population points. Creates classified raster surface

1) Open ArcGIS Pro and create a new blank map (Map.aptx)

Add Code-Point Open CSV as a Layer using the Map --> Add Data option
Create an Event Layer using X,Y cords by right-clicking on the Layer in the Contents panel --> Display X, Y Data
Select Field 3 as the X Field and Field 4 as the Y Field
Set the Spatial reference to be British_National_Grid
Click Run
Export Features by right-clicking on the Layer and selecting Data --> Export Features
Create a Shapefile called Code_Point_Pro.shp (no dashes)
Click Run

2) Create Address Locator

Open the Toolbox (if it’s not visible go to Analysis tab) and go to Geocoding Tools -->Create Address Locator
Address Locator Style – General Single Field
Reference Data – Code_Point_Pro.shp
Field Map --> KeyField --> Field1 (the field with the postcodes in it)
Output Address Locator – AddressLocator
Click Run

3) Geocode Population Postcodes

Use Toolbox --> Geocoding Tools -->Geocode Address
Input Table: the population spreadsheet (.csv)
Input Address Locator: the Address Locator created above
Input Address Fields: Single Field
Alias Name: standard_postcode (the column in the .csv spreadsheet that has the postcode to be geocoded)
Output Feature Class Geocoded_Pop_pro.shp
Click OK
There will now be an attribute (USER_TOT_P) on each postcode point with the total population for that postcode.

4) Clip Population Postcodes to Wards Boundaries

First create a layer of just the City of Edinburgh wards
Load the Ward boundary dataset (district_borough_unitary_ward.shp) using Add Data…
Use Select by Attribute and Selection type “New Selection”.
Create an SQL query Expression Add Clause --> Values --> FILE_Name is Equal to CITY_OF_EDINBURGH
Click on Add
Invert Where Clause
and then Run
Delete selected features as these are wards outside of Edinburgh
Now delete population features outside of Edinburgh
Select by Location
Input Feature Layer: Geocoded_pop_pro
Relationship: Within
Selecting Features (district_borough_unitary_wards (just City of Edinburgh)
Invert spatial relationship – toggle on
Run

Go to Edit tab and Delete all population features outside of Edinburgh

5) Create Graduated Symbol Map of Population per Ward

Do a Spatial Join to calculate the population within each Ward area from all the Postcodes with population in that Ward. Note this form is different from the Desktop one.

We need to add ‘counts’ to all the Ward polygons of points that match the criteria.

Right click on the Wards dataset --> Joins and Relates --> Spatial Join
Target Features: the Ward boundaries (district_borough_unitary_ward)
Join Features: Geocoded population points (Geocoded_Pop_pro)
Output Feature Class: the name of the output shape file (Wards_pop.shp)
Join Operation: Join one to one
In Output Fields select: USER_POP_P
Change Merge Rule to Sum
Set Match Option to be: Completely contains

Click Run and a new Shapefile will be created that has the counts of geocoded points matching the query criteria on each polygon.

NOTE : You may need to Save and reload ArcGIS Pro for the polygons to be displayed

6) Symbolize Ward Population Data

Set up symbology (e.g. gradient, points symbols etc.) on the newly created Ward_pop dataset using the different attributes for the different maps:

Use the Appearance --> Symbology tab to set up suitable representations using Graduated Symbols
Select the Wards_pop layer the select the Appearance then Symbology --> Graduated Symbols
Field: USER_TOT_P
Change the colour by clicking on the symbol next to ‘Template’, go to the Properties tab and select Color.
Change the Background to be “Black Outline”
Add Text Labels to map based on Ward names.
Right Click on the Wards _pop layer and select Label
Then select Labeling Properties and change the size and appearance as needed (e.g. add a halo).

7) Create a Population Density Map

Use the Geocoded population features to create a ‘Density’ map

Use Geoprocessing --> Toolboxes --> Spatial Analyst Tools --> Density --> Point Density
Input point features: Geocoded_pop_pro
Population field: USER_POP_P
Output raster: Ed_Pop_Den (note name can’t be longer than 13 characters)
Set Output Cell size to be 50m
Set Neighborhood Radius to be 1000m

8) Add a Basemap

Add an OS Basemap to give the map context.

Add Basemaps –Map --> Basemap --> OS Open Background
Change Transparency of Population Density layer to be 20 %
Select the Point Density layer (Ed_Pop_Den). Go to the Appearance tab and move the slider in the Effects group.
Change the lowest colour range to be “No Color” by right-clicking on it.