How to create Graduated Symbol and Density maps Using ArcGIS Desktop, ArcGIS Pro and ArcGIS ...

29 Pages·2016·2.01 MB·English

How to create Graduated Symbol and
Density maps Using ArcGIS Desktop,
ArcGIS Pro and ArcGIS Online – a
comparison guide

Guy McGarva, EDINA, Feb 2016
Contents
Introduction ............................................................................................................................................ 3
Create Graduated Symbol and Density Maps from Geocoded data .................................................. 3
Summary of Processes ........................................................................................................................ 4
Using ArcGIS Desktop (10.3.1) ................................................................................................................ 5
1) Create an Address Locator in ArcGIS Desktop ............................................................................ 5
2) To get Population by Postcode Unit ........................................................................................... 6
3) Geocode Spreadsheet of Population by Postcode...................................................................... 6
4) Clip the data to an existing Spatial Extent .................................................................................. 7
5) Create Map of Population per Ward .......................................................................................... 8
6) Symbolize Ward Population Data ............................................................................................... 8
7) Population Density Map.............................................................................................................. 8
8) Add a Basemap ......................................................................................................................... 10
9) Final Map................................................................................................................................... 11
Using ArcGIS Pro (Vers 1.1.1) ................................................................................................................ 12
1) Open ArcGIS Pro and create a new blank map (Map.aptx) ...................................................... 12
2) Create Address Locator ............................................................................................................. 12
3) Geocode Population Postcodes ................................................................................................ 13
4) Clip Population Postcodes to Wards Boundaries ...................................................................... 14
5) Create Graduated Symbol Map of Population per Ward ......................................................... 15
6) Symbolize Ward Population Data ............................................................................................. 16
7) Create a Population Density Map ............................................................................................. 16
8) Add a Basemap ......................................................................................................................... 17
9) Final Map in ArcGIS pro ............................................................................................................ 18
Using ArcGIS Online (Feb 2016) ............................................................................................................ 19
1) Geocode Population Postcodes ................................................................................................ 19
2) Display Geocoded Population on Map ..................................................................................... 20
3) Add Ward Boundary Data to Map ............................................................................................ 21
4) Select City of Edinburgh Wards ................................................................................................. 22
5) Clip Population Points to City of Edinburgh Ward Boundary ................................................... 22
6) Create map of population per ward ......................................................................................... 23
7) Symbolize Ward Population Data ............................................................................................. 25
8) Create Density map of Edinburgh Population .......................................................................... 26
9) Set up Symbology ...................................................................................................................... 27
10) Final Map in ArcGIS Online ................................................................................................... 29
Introduction
This document aims to show how to carry out similar GIS processes in the evolving Esri offerings of
ArcGIS Desktop, ArcGIS Pro and ArcGIS Online, especially as Pro and Online are relatively new
products and unfamiliar in their capabilities to many.
We will use a simple example GIS process of creating a Graduated Symbol map and a density map
that could be used for teaching and learning purposes. It will show the use of Digimap data in the
different Esri GIS products.
Create Graduated Symbol and Density Maps from Geocoded data
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) A shapefile of boundaries of Wards downloaded from Digimap Ordnance Survey Data
Download.
b) 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.
c) 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.
d) A background OS map.
Summary of Processes
Step Process Description ArcGIS Desktop ArcGIS Pro ArcGIS Online
1 Create an Address Locator Use ArcToolbox to Create Address Use in-built
to Geocode postcodes create an Address Locator using Geocoder or
using Code-Point Open Locator Geocoding Tools Geocode
data. Toolbox externally e.g. in
Geoconvert
2 Geocode addresses Geocode Input Geocode input Add CSV to
source (postcode) source (postcode) Online content
data as CSV data as CSV. and geocode
using Esri
Geocoder.
Note: Uses about
1000 credits to
geocode 25,000
points.
Instead, use
Geoconvert
3 Clip points to spatial Select by Location Select By Location Use the Analysis
boundary within area of within Ward Tool  Find
interest, invert boundaries. Existing Locations
selection and Invert spatial and query for
delete features relationship points inside
outside area. before query to area. Creates a
delete all those new layer.
features outside
the area.
4 Calculate populations Spatial Join Do a One to One Use the Analysis
within boundaries between Wards Spatial Join and Tool 
and Geocoded Sum the Summarize Data
population data attributes for  Summarize
and Sum the population total Within to create
attributes for attributes for layer with Ward
population population populations
5 Classification and Display using Display using Display using
Symbology classified classified classified
graduated graduated symbol graduated
symbols or or colours symbols or
colours colours
6 Create Density Map Use Point Density Use Point Density Use the Analysis
Toolbox on Toolbox on Tool  Analyze
Geocoded geocoded Patterns 
population points. population Calculate Density
Creates classified points. Creates to create a vector
raster surface classified raster dataset of
surface classified
polygons
Using ArcGIS Desktop (10.3.1)
1) Create an Address Locator in ArcGIS Desktop
This will be used to geocode the postcodes, enabling them to be mapped.
 Download postcode data for Edinburgh from Digimap:
o Use the Code-Point Open data for Edinburgh
o The data is supplied in CSV format in a zip archive
o Unzip the data from the archive

 Add the postcode data to ArcGIS using the Add Data... function
 Right click on the layer in the Table of Contents  Display XY Data…
 Choose FIELD3 and FIELD4 for the coordinate fields
 Set the coordinate system to British National Grid
 Click OK (Ignore warning about no Object-ID field)
 The data will be add to ArcMap as an Events layer
 Right click on the events layer then Data  Export Data… to export the data as a new
Shapefile. (e.g. code-point.shp)
 Add the new shapefile to ArcGIS
 Remove the events and csv data table as they’re no longer required.

Next, create an Address Locator in ArcGIS using the downloaded Shapefile of postcodes for
Edinburgh.
 In ArcToolbox navigate to Geocoding Tools  Create Address Locator,
 Use the ‘General - Single Field’ style as the Address Locator Style
 Select the shapefile created above as your Reference Data,
 Set the ‘Field1’ field from the postcode data as the Key Field.
 Specify a suitable name location (i.e. a new folder) for the ‘Output Address Locator’ e.g
EH_Address_locator.
 Click OK
2) Get Population by Postcode Unit
 Go to: http://geoconvert.mimas.ac.uk/index.html
 Start Geoconvert
 Select “Information about Postcodes” and select Next
 Select 2011 UK Census postcode lookup and select Next
 Select “Postcode populations”  “Usually resident persons” and select Next
o NOTE: You can also get the location of postcodes directly from Geoconvert but
we will not do that as we want to show the generic geocoding functionality in
ArcGIS.
 Supply a File of Postcodes, Comma separated with no header and select the location of
the Code-Point Open csv dataset (eh.csv). Select Next
 Note some postcodes won’t be matched because they are not residential addresses and
so have no census data.
 Select the Postcode Metadata and Save the file e.g. EH_matched.csv

3) Geocode Spreadsheet of Population by Postcode
Geocode the Population potcodes data
 Open the Geocode Addresses tool: ArcToolBox  Geocoding Tools  Geocode
Addresses.
 In the Input Table field browse to the .csv spreadsheet of population points that have
been downloaded from Geoconvert.
 Select the Address Locator created in step 3 above in the Input Address Locator field.
 In the Input Address Fields table select “Single Field” and ensure that the Alias Name
field name is set to the column that contains the postcodes in the spreadsheet
(standard_postcode).
 Specify a suitable output file location and name (e.g. Geocoded_pop).

The geocoded Population dataset will be added to ArcMap once the process has completed.
 Open the attribute table of the geocoded population data and check the points have all
the necessary attributes (including one called TOT_PERS11 which is the total number of
persons at that postcode)

4) Clip the data to an existing Spatial Extent
We only want a map showing the population within the boundary of the City of Edinburgh.
The EH postcode extends outside of the City of Edinburgh.
 First create a layer of just the City of Edinburgh wards
 Load the Ward boundary dataset (district_borough_unitary_ward.shp)
 Use Selection  Select by Attribute and Select * FROM district_borough_unitary_ward
WHERE “FILE_Name” = “CITY_OF_EDINBURGH”
 Create a layer from selected features by right clicking on the Ward layer then Selection
 Create layer from Selected Features
 Second, start editing the Geocoded Population dataset
 Select all Geocoded population points inside the Ward boundaries using Select by
Location
o Target layer: Geocoded_pop
o Source layer: district_borough_unitary_ward selection
o Spatial selection method: are within the source layer feature
 Invert/Switch selection (this will change the selection to all those features outside the
boundaries). Right click on Geocoded_pop layer Selection  Switch Selection
 Delete the selected postcode points outside of Edinburgh by using Edit  Cut
 Stop Editing on the Geocoded_pop layer and Save edits

5) Create Map of Population per Ward
Do a Spatial Join to calculate the population within each Ward area from all the Postcodes in
that Ward. Add ‘counts’ to all the Ward polygons of points that match the criteria.

 Right click on the Wards (polygon) dataset and select Joins and Relates  Join…
 Select ‘Join data from another layer based on spatial location’ in the top drop down
menu.
 In Step 1 select the geocoded population dataset
 In Step 2 select the first toggle button (Each polygon will be given a summary…)
 Select Sum from the list of how you want the attributes to be summarized
 In Step 3 specify an appropriate name for the output Shapefile (e.g. wards_pop_counts)
 Click OK and a new Shapefile will be created that has the counts of geocoded points
matching the query criteria on each polygon (the value will be in the attribute
“Sum_TOT_PE”.

6) Symbolize Ward Population Data
Set up symbology (e.g. gradient, points symbols etc.) on the newly created dataset using the
different attributes for the different maps:
 Bring up the Properties dialog for the layer by double clicking on it or right click 
Properties
 Symbology tab  Quantities  Graduated Symbols and select Sum_TOT_PE for the
Value
 Change Background colour to be Hollow
 Add Labels to map based on Ward names
 Right click on the Wards layer and select Symbology then toggle the “Label features in
this layer” On
 Set up the properties of the labels e.g the Label Field should be Name, Text size 8pt and
Halo should be 1px
 Use Maplex for better positioning

7) Population Density Map
Create a population density map from the geocoded population points.
 Use ArcToolbox  Spatial Analyst Tools  Density  Point Density
 Input point features: Geocoded_pop
 Population field: TOT_PERS11
 Set Output Cell size to be 50m
 Set Neighbourhood Radius to be 1000m
 Click OK
 The population density map will be loaded into ArcMap

 Set up Symbology for the generated Density map by selecting the Layer Properties 
Symbology tab
 Use a Classified symbology by classifying the result into 9 classes using Natural Breaks
 Choose a suitable colour ramp (e.g. blue)
 Change the first value to be “No Color”
 Click OK
 Set Transparency of Layer to be 50%: right click on layer and select Properties… 
Display tab and change Transparency to 50%

8) Add a Basemap
 Add Basemaps – OS Open Background from the Add Basemap menu