Map Scales and Direction on Maps

Types of Map Scales

Bar Scale (Graphic Scale)

• A bar with divisions labeled to represent distance.
• Useful on modern computer maps where numerical scales can vary with display size and zoom level.
• Expands or shrinks consistently with the map.
• Common in computer applications like Google Maps.

Ratio Scale on US Geological Survey Maps

• Example: Long Beach map with 1 to 24,000 ratio.
• Includes three bar scales: miles, feet, and kilometers.

Classification of Map Scales

Large Scale

• 1 to 24,000
• Example: Long Beach map.
• High detail, small area.
• Shows individual streets and some building shapes.

Medium Scale

• 1 to 62,500
• One inch approximately equals one mile.
• Intermediate detail, intermediate area.

Small Scale

• 1 to 250,000
• One inch equals about four miles.
• Covers large area, less detail.

Usage and Comparison of Scales

• Small Scale Map: Good for a general overview, major roads, and geography.
• Medium Scale Map: Better detail, some road intricacies.
• Large Scale Map: Most detailed view, individual streets and some buildings.

When to Use Bar Scale vs Ratio Scale

• Bar Scale: Quick approximations (e.g., eyeballing distances).
• Ratio Scale: Accurate measurements (e.g., infrastructure projects).

Map Direction

Determining North

• Maps commonly have "north" at the top, but not always (e.g., road atlases).
• North arrows help indicate direction; may be decorative or subdued.

Notable Example: Llandudno Beach Map

• Map printed upside down to suggest the north-facing beach is south-facing.
• North arrow is small and points down.

North Arrow on USGS Maps

• Indicates true north with a star symbol representing Polaris.

Conclusion

• Both bar scales and ratio scales have their uses depending on the need for precision.
• Understanding direction on maps is crucial and can vary based on map orientation.