Home / Tutorials

Basic Mapping With ArcGIS Online

The dominant company in geographic information systems is ESRI, which was one of the pioneers of GIS in the late 1960s. If you do GIS professionally, you will probably be working with ESRI software.

ESRI's cloud-based service is called ArcGIS online, which is available by subscription, and which can be used to create web maps and perform some types of spatial analysis. The ArcGIS Online web app makes web map creation comparatively easy by providing online access to a flexible visualization and analysis tool, as well as easy access to both public and proprietary data.

Getting ArcGIS Online

You can get an ArcGIS Online account in one of three ways.

Enterprise Account

If your school or employer has an ESRI site license, you can get an account from your instructor or IT staff. The video below shows how to log in to ArcGIS Online using an enterprise account such as that used at Farmingdale State College:

ArcGIS For Personal Use

You can purchase an annual license from ESRI for personal use (as opposed to commercial use) for $100 that includes not only authorization for their desktop products (ArcMap and ArcGIS Pro) but also ArcGIS Online. The ArcGIS Online subscription comes with a limited number of credits, although you can purchase more as needed for a significant cost.

Free Public Accounts

ESRI provides free public accounts that provide basic capabilities to give you a feel for what ArcGIS Online can do. Public accounts include no proprietary data or analysis tools, which limits users to creating simple maps.

Geospatial Data

To create a map, you need geospatial data.

Geospatial data is what is where. Geospatial data indicates what things or characteristics (what) are at specific locations on the surface of the earth (where).

Where: Latitude and Longitude

Locations on the Surface of the Earth

The earth is a spheroid. It is round like a ball or sphere but flattened by slightly by the centrifugal force of rotation. The earth is 24,900 miles circumference, but around 27 miles wider than it is tall.

Locations on the earth are commonly expressed as coordinates consisting of two numbers: latitude and longitude.

Latitude and longitude are angles that describe where locations are relative to the center of the earth. Angles are measured in degrees, with one degree representing 1/360th of a circle.

While we think of and experience distances on the planet in terms of length (feet, miles, kilometers) rather than angles (degrees), the earth is lumpy and actual distances across the surface of the planet depend on how high you are (distance from the center of the earth). Even if the earth's surface were perfectly smooth, manipulating distances across a three-dimensional surface requires fiendishly complex calculations. Specifying locations in degrees is simpler and more accurate than specifying locations in distances.

Latitude

Since the earth is a three-dimensional object, two angles are required to specify locations on the surface of the earth.

Latitude is a location's distance north or south from the Equator, which is an imaginary line around the middle of the earth.

Latitudes range from +90° at the North Pole, to 0° at the Equator, to -90° at the South Pole.

Longitude

Longitude is a location's distance east or west from the Prime Meridian, which which was defined by an international agreement made at a conference in Washington, DC in 1884 to be at a naval observatory in Greenwich, England.

The longitude at Greenwich is 0°, with positive longitudes east of Greenwich, and negative longitudes west of Greenwich.

Longitudes range from -180° to +180°.

Unlike latitude, which can be measured based on the poles and the Equator, there are no unambiguous environmental markers to define where longitude zero should be. Greenwich was chosen because England was at the height of its maritime dominance and, accordingly, many maps of the time already used Greenwich as longitude zero (Alfred 2010).

Decimal vs. Degrees-Minutes-Seconds Format

Google Maps and other applications will sometimes display latitudes and longitudes in a traditional degrees-minutes-seconds format, with a minute being 1/60th of a degree and a second being 1/16th of a minute. North (N) or South (S) means north or south of the Equator, and East (E) or West (W) means east or west of the Prime Meridian.

38° 53' 50" N, 77° 02' 12" W

If you have latitudes/longitudes in this format, you need to convert them to decimal numbers because most GIS software cannot understand coordinates in degrees-minutes-seconds format. Entering coordinates in the Google Maps search bar will show both formats. There are also a number of online calculators you can use to convert.

What: Attributes

Attributes are the what part of what is where. Attributes are also sometimes referred to as fields, columns, or variables.

Types of Attributes

The type of attribute you are mapping determines what type of map is most appropriate.

There are four types of attributes you need to be aware when mapping in ArcGIS Online:

1. Names (Nominal): The names of things
   • Place names like city, state, or country names (New York, NY)
   • Names of structures (Empire State Building)
   • Descriptions (Concert hall built by industrialist Andrew Carnegie and opened in 1891)
2. Categories (Categorical): Names that group things into categories
   • Geographic regions (Northeast, Southwest, etc.)
   • Political affiliations (Democratic, Republican, Green, Independent, etc.)
   • Yes or No (dichotomous)
3. Counts: The number of things in a location. Things that are counted
   • Population (there are no half people)
   • Number of votes
   • Number of days
4. Amounts: The amount of something at a location. Things that are measured
   • Medians and averages (central tendency)
   • Elevation (height above sea level)
   • Temperature

Units

Quantitative attributes always have a unit, which is a name that indicates what the numbers represent. A number without a unit is meaningless. For example, the number 70,000 means nothing by itself, but $70,000 in household income makes that number useful.

With geospatial data, units should include four clarifying components:

• Categorical component: What is the phenomena being measured?
• Mathematical component: What mathematical unit is used?
• Spatial component: What area is being covered by each of the values?
• Temporal component: What range of time is covered by each value?

For example, if you have data for Stroke mortality per 100K residents by state in the year 2016:

• Categorical component: stroke mortality (rate of death by stroke)
• Mathematical component: per 100,000 residents
• Spatial component: by state
• Temporal component: in the year 2016

Mapping Points From CSV Files

Creating a CSV File In Google Sheets

Comma-separated variable (CSV) files are spreadsheet files that can be saved from any desktop spreadsheet program (like Excel) or from Google Sheets. CSV files that contain addresses or latitudes/longitudes can be imported as layers in ArcMap.

This video shows the creation of a CSV file in Google Sheets of houses of worship in the Farmingdale, NY area.

1. Go to Google Drive and log in using your Gmail credentials
2. Select New, Google Sheets
3. Add the headers to each column that represent the attributes you want to map for each location. Add columns titled Latitude and Longitude where you will provide the coordinates for the locations
4. Add a latitude, longitude, and attributes for each location you want to map
5. Change the title of the spreadsheet to something meaningful. Note that Google Sheets automatically saves data as you go
6. If you want to share the spreadsheet with someone, click the Share button, Get Sharable Link, select the amount of sharing desired, copy the link, and submit that link to the person with whom you want to share the spreadsheet

Capturing Latitude and Longitude With What's Here in Google Maps

Latitudes and longitudes for locations can be captured using the What's Here tool in Google Maps.

1. Right click on the location where you want the latitude and longitude
2. Select What's Here
3. Click on the latitude/longitude in the pop-up box
4. Copy the latitude/longitude from the right pane. Always use the decimal format (smaller numbers on the bottom) rather than the degrees-minutes-seconds format (larger numbers on the top with the additional symbols)

Single Symbol Point Maps

The simplest form of point maps uses a single symbol for all locations being mapped.

1. Download as CSV your spreadsheet as a .csv file. In a spreadsheet program, you can Save As with a type of Text CSV
2. From your ArcGIS Online home page, select Map to create a new map
3. In ArcGIS Online, Add, Add Layer from File
4. If you have named your location fields latitude and longitude, the app will automatically map your points as dots. If you misspell latitude or longitude, or you want to map your points from addresses or other types of names, you will be given a dialog box asking what fields to use for what types of locations
5. Under Choose an attribute to show, select Show location only
6. Under Select a drawing style, click Options and select a symbol to use for the points. These can be simple symbols like circles, or pictograms
7. If desired, add labels to the bubbles by clicking on the ellipsis on the layer and selecting Create Labbels. Choose a label alignment where there is the least amount of overlap and contention for your particular set of locations
8. Save the map under a meaningful name
9. Share the map to get a link

Categorical Pictogram Maps

If you have a categorical variable, you can use ArcGIS Online to create a map where the type of symbol varies depending on that categorical variable. Pictograms are small images that have literal or metaphorical relationships to the locations being mapped.

For this example, we use a spreadsheet of houses of worship in the Farmingdale area.

1. Download as CSV your spreadsheet as a .csv file. In a spreadsheet program, you can Save As with a type of Text CSV.
2. In ArcGIS Online, Add, Add Layer from File.
3. If you have named your location fields latitude and longitude, the app will automatically map your points as dots. If you misspell latitude or longitude, or you want to map your points from addresses or other types of names, you will be given a dialog box asking what fields to use for what types of locations.
4. For categorical variables, you will probably want the Types (Unique symbols) drawing style.
5. For Options click on the icons under each category to choose and size appropriate pictograms.
6. If needed, rename the layer to that the title of the legend is meaningful.
7. If desired, add labels to the pictograms by clicking on the ellipsis on the layer and selecting Create Labbels. Choose a label alignment where there is the least amount of overlap and contention for your particular set of locations.
8. Consider changing the base map to something unobtrusive if the base map conflicts visually with the points.

Quantitative Bubble Maps

For quantitative variables, Counts and Amounts (Size) can be used to create bubble maps.

1. Download as CSV your spreadsheet as a .csv file. In a spreadsheet program, you can Save As with a type of Text CSV
2. In ArcGIS Online, Add, Add Layer from File
3. For Choose an attribute to show, select your quantitative variable
4. For quantitative variables, you will probably want the Counts and Amounts (Size) drawing style
5. If desired, add labels to the bubbles by clicking on the ellipsis on the layer and selecting Create Labbels. Choose a label alignment where there is the least amount of overlap and contention for your particular set of locations
6. Consider changing the base map to something unobtrusive if the base map conflicts visually with the points
7. Save the map with a meaningful name
8. Share the map with Everyone (public) and copy the shared link that you can e-mail or submit for an assignment
9. If you are embedding the map on a web page, you can also get iframe code from the sharing dialog

Mapping Shapefiles

Many organizations, including federal, state and local governments, make data available to the public as shapefiles, which is an old file format developed by ESRI in the 1990s that is still commonly used for sharing data. A shapefile is actually multiple files, but shapefiles are often packaged as single .zip files for easier distribution.

For this example, we use this shapefile state election data.

• Download the shapefile to your local storage drive
• Select Add, Add Layer From File to upload the shapefile
• Style the layer based on a field in the shapefile. For this example we will use the winner of the 2012 presidential election (WIN2012), coloring states won by the Republican candidate (Romney) red and states won by the Democratic candidate (Obama) blue, in accordance with common conventions
• As before, zoom, save and share

Living Atlas Layers

ESRI's Living Atlas of the World is a collection of open and proprietary data that is made available in ArcGIS Online. Living Atlas layers cover a wide variety of topics.

Creating a Map

1. Select Map from your ArcGIS Online home page
2. Click the Add button and Browse Living Atlas Layers
3. Search for your topic of interest. For this example we will use 2016 Median Household Income
4. For polygon layers, adjusting the transparency to 25% will permit the base map to be visible and give geographic context to your layer so you know where things are
5. Zoom the map to your area of interest
6. View the legend to see what the colors or symbols mean
7. With many layers, you can click on a region to display a pop-up displaying information about that region

Generalization

Web maps are designed so that you can zoom in or zoom out, and those different zoom levels are numbered, from one showing the whole world, to 21 or greater, which shows building-level detail.

Many Living Atlas layers provide different levels of cartographic generalization based on the zoom level. This optimizes the amount of data displayed at different scales, so maps do not appear either too cluttered, or too lacking in detail to be meaningful. With this median household income layer:

• When zoomed in close to an area, this layer displays census tracts or block groups
• Zooming further out, the data is generalized to the county level
• Further out, the data is generalized to the state level
• As with many layers, you can click on a region to display a pop-up displaying information about the region displayed at that particular level of generalization

Adding Map Notes

Map notes are layers of annotations that can be used to point out specific locations or features on a map.

1. Select Add, Add Map Notes
2. Give the map notes layer a meaningful name
3. Pan to the area you want to annotate
4. Select the type of note you want to add in the left pane, then click on the map to add it
5. Give the annotation a meaningful name and, if needed, annotation text
6. When you are done adding notes, click the edit button to stop editing
7. If you later want to add additional map notes to an existing map notes layer, select the layer in the Contents pane and click the Edit button

Finding Latitudes and Longitudes

If you need the latitude and longitude in ArcGIS Online, you can use the Location tool and click on the map to find the latitude and longitude. Those latitudes and longitudes can be pasted into Google Maps if you want to find neighborhood names or get or share street views of a location.

Sharing a Map

Sharing controls who can see your map.

1. Zoom to the view that you want visitors to see when they first open your map
2. Save (or Save As) your map under a meaningful name. Include tags such as the name of the layer or the location being mapped
3. Click the Share button. ArcGIS Online is oriented around creating maps for the web, so you will usually want to share with Everyone.

4. You can then copy the provided link to include in an e-mail or assignment submission

Note that depending on the authorization provided by your account administrator, Living Atlas layers may not be accessible to people outside of your organization and will throw a warning message. You can view such layers by logging in when viewing the map.

Starting a New Map

When you are done editing a map, if you want to close the existing map and start a new map, save the existing map, and then click the New Map link at the top left.

Reopening a Map

Maps that you save are listed on your Content page in ArcGIS Online. To reopen the map for modification or revision, select the link on your content list and then Open in Map Viewer.