📚 CTEVT | Fundamental of Surveying & Geomatics – Chapter 5: Map Scale
(Full Notes + Practice Questions + Free PDF)
Map Scale is one of the most important and foundational topics in surveying and cartography.
Without scale, measurements on maps would have no meaning.
Chapter 5 teaches how scale is expressed, constructed, used, and corrected.
This chapter is heavily used in:
✔️ Map reading
✔️ Plotting
✔️ Measurement conversion
✔️ Engineering drawings
✔️ Cadastral & topographic mapping
🧩 Chapter Overview: Map Scale
Map scale = The ratio between a distance on the map and the corresponding distance on the ground.
Chapter 5 explains:
✔️ What a scale is and why it is important
✔️ Types of scales used in surveying
✔️ Construction of graphical scale
✔️ Shrunk scale & shrinkage factor
✔️ Errors due to wrong scale
✔️ Enlargement and reduction of scale
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🔍 5.1 Introduction to Map Scale
A map is a scaled representation of a large area.
⭐ Why Scale is Essential
✔️ Gives meaning to map distances
✔️ Helps calculate ground distance, area & location
✔️ Ensures uniformity in mapping
✔️ Allows comparison between maps
✔️ Needed for design, planning & fieldwork
Without a proper scale, a map becomes just a picture.
🔍 5.2 Expression & Types of Map Scale
Scale can be expressed in three common ways:
⭐ 1️⃣ Statement Scale
Expressed in words.
Example:
✔️ “1 cm represents 100 m”
✔️ “1 cm = 50 m”
✔️ “1 inch = 1 mile”
Easy to understand but not useful for calculations.
⭐ 2️⃣ Representative Fraction (RF)
Given as a ratio:
Example:
-
1 : 50,000
-
1 : 10,000
-
1 : 2,500
✔️ No units involved
✔️ Most precise form
✔️ Used in topographic maps
Formula:
RF = (distance on map) / (distance on ground)
⭐ 3️⃣ Graphical (Bar) Scale
A line or bar divided into distances.
✔️ Advantages
-
Useful even when the map is enlarged/shrunk
-
Easy to measure
-
Works even with photocopies
Graphical scale is the most practical type for field use.
🔍 5.3 Construction of Graphical Scale
Steps to draw a graphical scale:
1️⃣ Select suitable length (e.g., 10 cm).
2️⃣ Convert ground distance using RF.
3️⃣ Draw a line representing the scale.
4️⃣ Divide it into equal parts.
5️⃣ Show subdivisions for precise measurement.
6️⃣ Label the units clearly.
Example
RF = 1 : 50,000
1 cm = 500 m
10 cm = 5 km
→ Draw a 10 cm long bar scale representing 5 km.
🔍 5.4 Scale and Graphical Error
Even when a scale is drawn correctly, errors can occur due to:
✔️ Wrong plotting
✔️ Incorrect subdivision
✔️ Inaccurate measuring tools
✔️ Expansion or shrinkage of paper
This may distort measurements on the map.
🔍 5.5 Shrunk Scale & Shrinkage Factor
Maps shrink due to humidity, temperature, old age, or lamination.
If original length = L
Shrunk length = Lₛ
⭐ Shrinkage Factor (S)
S = Lₛ / L
⭐ Shrunk Scale
New RF = Old RF × S
Shrunk scale is used to adjust the measurements on an old or damaged map.
🔍 5.6 Importance & Uses of Map Scale
✔️ Helps calculate ground distance
✔️ Enables measurement of area and location
✔️ Used in plotting, map comparison, and fieldwork
✔️ Required for engineering drawings
✔️ Needed for cadastral surveying and mapping
✔️ Essential for GIS and cartography
Almost every surveying task depends on the scale.
🔍 5.7 Effect of Using Wrong Scale
Using a wrong scale can cause:
❌ Wrong distance
❌ Wrong area
❌ Incorrect plotting
❌ Misinterpretation of land parcels
❌ Engineering design failures
Example:
If scale used = 1 : 1000
But actual map scale = 1 : 2000
→ Distance and area will be double the real value.
🔍 5.8 Enlargement & Reduction of Scale
Maps may need to be enlarged or reduced.
⭐ Enlargement
Increasing map size → New scale becomes larger
Example: From 1:50,000 → 1:25,000
⭐ Reduction
Decreasing map size → New scale becomes smaller
Example: From 1:10,000 → 1:20,000
⭐ Formula
New RF = (old RF × multiplying factor)
Enlargement and reduction must maintain proportional accuracy.
🧪 Practical Uses
Map scale is directly applied in:
📍 Plotting survey data
📍 Field measurements
📍 Area calculation
📍 Drawing maps in practicals
📍 Using map for navigation
📍 Cadastral mapping
📍 Topographic mapping
📍 GIS digitization
Mastery of scale is essential for all surveyors.
📝 Short Questions
1️⃣ Define map scale.
2️⃣ What is representative fraction (RF)?
3️⃣ Give two examples of statement scale.
4️⃣ What is a graphical scale?
5️⃣ What is shrinkage factor?
6️⃣ Convert RF 1:25,000 into statement scale.
7️⃣ What is the effect of using wrong scale?
8️⃣ What is enlargement?
📝 Long Questions
1️⃣ Explain the types of scale with examples.
2️⃣ Describe the procedure for constructing a graphical scale.
3️⃣ Define shrunk scale and derive its formula.
4️⃣ Explain the errors caused by wrong map scale.
5️⃣ Discuss enlargement and reduction of scale.
🎯 Key Takeaways
✔️ Scale gives meaning to all map measurements.
✔️ Three main types: statement, RF, and graphical.
✔️ Shrinkage affects old/damaged maps.
✔️ Wrong scale leads to large errors.
✔️ Scale is essential for map reading, plotting, and analysis.
📂 Download Free PDF Notes – Chapter 5
🔽 [Download Notes – Chapter 5 (PDF)]
🎥 Watch the Full Chapter 5 Video
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📘 Explore More from Fundamental of Survey and Geomatics
📘 SYLLABUS – Download PDF
📘 Unit 1: Historical Background – Download PDF
📘 Unit 2: Introduction to Surveying – Download PDF
📘 Unit 3: Principles & Classifications – Download PDF
📘 Unit 4: Measurement Units – Download PDF
📘 Unit 5: Map Scale –Download PDF
📘 Unit 6: Linear Measurements – Download PDF
📘 Unit 7: Angular Measurements – Download PDF
📘 Unit 8: Map Reading – Download PDF
📘 Unit 9: Measurement Errors – Download PDF
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