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ArcGIS

ArcGIS Online Georeferencing

This tutorial will show you how to georeference historical maps using ArcGIS Online as of 2023. Georeferencing is a process that binds images to coordinates on a map, making a historical map image connected to a virtual map with accurate coordinate systems.

Set up

In preparation for this tutorial, you will need...

  • An Organizational Account for ArcGIS Online (this includes Brock affiliates)
  • A high resolution JPG or PNG file of a map
  • Internet Access

Getting Started

  1. Go to arcgis.com and click Sign In > Your ArcGIS Organization's URL
  2. Type "Brock" to complete the URL, click Next
  3. Click Brock University and authenticate using your valid Brock credentials.

NOTE: If you are affiliated with another institution, use that organization's URL instead of the one above.

Georeferencing

  1. Click Map from the options at the top of the window.
  2. Use the search tool (or zoom and pan) to find the city of St. Catharines in Ontario, Canada.

map of St. Catharines, Ontario Canada

  1. Click the down arrow beside Add to see the options for adding to your map. Click Add Media Layer.

Image showing the Add media layer option

  1. Drag the map image file (JPG or PNG) to the window or browser Your Device.

Add media dialogue box to add a map image

  1. The view shifts to georeferencing view. You will see the historical map overlaid on the basemap.

Georeferencing step one shows a map image overlaid on the base map

  1. To understand the options for adjusting the image, click the lightbulb in the top left corner of the view.

Help tips list for georeferencing

  1. Shift and adjust the image according to the help tips. NOTE: Clicking 'Reset' will allow you to start from scratch.

Rotated historical map overlaid on base map

  1. When you are satisfied with the position of the map, click Update and Close. The map image is now georeferenced and will appear without the transparency.

Georeferenced historical map overlaid on the base map

  1. If you need to make any changes to the georeferencing/position of the historical map, click Edit Placed Media from the options on the right.
  2. Make your adjustments and click Update and Close. 

We use georeferencing to get a close approximation of the two maps to fit, but they will never be perfect.

It is okay and inevitable that your historic map will be skewed in this process. Aim to have your map fit as well as it can, and still be legible.

Saving your map

  1. From the layer listing to the left of the map view, click the horizontal 3 dots beside the historical map name and click Save As.
  2. In the Save as dialogue box, enter an appropriate Title, Tags (keywords to help find the map), and Summary (brief description of the historical map).

 

Save as dialogue box with Title, Tags, Summary of the historical map

  1. Click Save. The map is now linked to an item record in your content in ArcGIS Online.
  2. Adding a georeferenced media layer
  3. To find and share your media layer, follow these steps:
  4. Click the Add button  and notice the top item is the georeferenced media layer. Select it and click Add.
  5. From the Properties panel to the right of the map view, click the button beside the title  to open the FULL Item Properties window. 

Item Description window showing select metadata about the historical map

By default, the map is shared privately so no one else can access it.

  1. To share the georeferenced media layer, click the Share button from the right hand side and select Everyone (Public).

  1. Click Save.