Converting a scanned map into
GIS data
John McVay
• My Field of Study: Environmental Science
with a concentration in Community Land
Planning.
• Career Aspiration: work for a land trust
How can this skill be applied?
• Project that this information comes from
prioritized areas for habitat protection –
what some land trusts do.
• Sometimes work in remote areas with no
previously prepared GIS. Physical map
may be all you start with.
• As a planner, you can create new features in
GIS by sketching features on the scanned
map
But First… You Have to Get
Scanned Map Set Up in ArcGIS
How to do this:
• Open scanned image in ArcMap, click yes
to build pyramids.
• Set coordinate system
• Determine x,y coordinates for control points
- Zoom in enough so that you can read the
coordinates
- Coordinates along the top and ycoordinates down the left side
Adding Coordinates:
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Zoom in
Display the Georeferencing toolbar.
Click the View Link Table button
Click the Add Control Points button
Position the crosshair so that it lines up
precisely with the intersection of the blue tic
mark and the black line of the map border.
• Right-click and choose “input X and
Y.”
• Enter x and y coordinates
• Once all four coordinates added, to
permanently apply the transformation
to the data, you must use the “Rectify”
command from the Georeferencing
menu