Details

	None	do not include a scale
	Automatic	include an automatic scale
	"Metric","Imperial"	include a scale for a unit system
	unit	include a scale in a particular unit
	{d₁,d₂,…}	include a scale with scale divisions d₁, d₂, etc.
	{scale₁,scale₂}	include a scale with two sets of divisions
	Placed[scale,pos]	position the scale at position pos

The possible positions are:
{x,y} scaled position in the map

GeoPosition[lat,lon] specific geographic location

{pos₁,pos₂} end points for the scale
Scales are most accurate near the middle of the map and become distorted near the edges.
By default, scales are not shown if there would be too much distortion for the map.

Examples

Show a map of Champaign, IL with a scale in the bottom-left corner:

Wolfram Language code: GeoGraphics[Entity["City", {"Champaign", "Illinois", "UnitedStates"}], GeoScaleBar -> {"Imperial", "Metric"}]

Show the scale in kilometers:

Wolfram Language code: GeoGraphics[Entity["City", {"Champaign", "Illinois", "UnitedStates"}], GeoScaleBar -> "Kilometers"]

Show a map of the United Kingdom with a scale in the top-right corner:

Wolfram Language code: GeoGraphics[Entity["Country", "UnitedKingdom"], GeoScaleBar -> Placed["Kilometers", {Right, Top}]]

Show a scale of 100 kilometers:

Wolfram Language code: GeoGraphics[Entity["Country", "UnitedKingdom"], GeoScaleBar -> Placed[Quantity[{0, 100}, "Kilometers"], {Right, Top}]]

Top

	{x,y}	scaled position in the map
	GeoPosition[lat,lon]	specific geographic location
	{pos₁,pos₂}	end points for the scale