1.11. Units of Measurements

Measurements/observations are assigned specific units. In surveying, most commonly employed units are for length, area, volume, and angle. Two different systems are in use for specifying the units of observed quantities; the English (FPS) system and Metric system (MKS). Because of its widespread adoption, the metric system is also called the International System of Units (SI).

In surveying, every measurement we take is expressed in specific units, which helps standardize how we communicate and record our observations. There are two major measurement systems used worldwide: the English system (also known as the FPS - Foot, Pound, Second system) and the Metric system (or MKS - Meter, Kilogram, Second system). The Metric system is also recognized globally as the International System of Units (SI), which is widely used due to its consistency and ease of conversion.

Think of it like different languages. Just as people can communicate in English, Spanish, or Mandarin, measurements can be expressed in the English or Metric systems. If you’re traveling to a country that uses a different language, it’s helpful to learn a few key phrases. Similarly, for civil engineers working internationally, knowing both measurement systems is essential.

According to Standards of Weights and Measurements Act, India in 1956 decided to replace English (FPS) system used earlier with the MKS. In 1960, SI unit was approved by the conference of weights and measures.

In 1956, India adopted the Metric system to standardize measurements, moving away from the English system. This change aimed to facilitate trade, education, and scientific research by using a system that is simpler and more coherent across various applications. The SI units were officially recognized in 1960, setting a global standard for measurements.

Imagine switching from an old mobile phone that doesn't connect well to a new smartphone that has all the modern features and better connectivity. Similarly, the transition to the Metric system was aimed at improving efficiency and communication in measurements.

The major difference between MKS and SI is in the use of unit of force. In MKS unit of force is kg-wt (which is commonly called as kg only) while in SI it is newton.

While the MKS system uses kilograms to measure force (as in 'kilogram-force'), the SI system specifies force in newtons. This distinction is important as it highlights the transition to a more precise measurement of force, where one newton is defined as the force required to accelerate one kilogram of mass by one meter per second squared. This change supports scientific clarity and reduces confusion in calculations.

Think of kg-wt like the amount of push needed to lift a heavy box. In your local gym, you might measure weights in kilograms, but in science, you might describe the same push needed to lift that box in newtons to convey the precise force applied. By using newtons, it’s like using the precise language in mathematics.

In FPS unit, the length is measured in foot and inches. 1 foot = 12 inches 1 yard = 3 feet (ft.) 1 inch = 2.54 cm (basis of international foot) 1 meter (m) = 39.37 inches (basis of U.S. survey foot) 1 rod = 1 pole = 1 perch = 16.5 feet 1 Gunter’s chain = 66 feet = 100 links = 4 rods 1 mile = 5280 feet = 80 Gunter’s chains 1 nautical mile = 6076.10 feet (nominal length of a minute of latitude, or of longitude at the equator)

In the FPS system, various units are used to measure length, beginning with the foot, which can be divided into inches, or scaled up to yards, miles, etc. For civil engineers in the U.S., understanding these conversions is essential in their work, especially when planning constructions or surveying land. These units create a hierarchy of measurements that can be adapted to different scales of work.

Imagine measuring a room. If you're buying new furniture, you might measure it in feet and inches. If the store gives measurements in square footage, knowing how to convert between these units helps ensure your new couch fits perfectly! It’s like having a toolbox where each tool serves a specific purpose—the right measurement helps build the right kind of project.

In SI unit, the length is measured in centimeter, meter, and kilometer. 1 m = 10 dm (decimeter) 1 m = 100 cm 1 m = 1000 mm (millimeter) 1000 m = 1 km (kilometer) 1 km = five eighths of a mile

In the SI system, lengths are measured in meters, with subdivisions (like centimeters and millimeters) and larger units like kilometers. This decimal-based system makes it straightforward to convert between units by simply moving the decimal point. For example, converting meters to kilometers requires dividing by 1000, making calculations easy and intuitive.

Think of the Metric system like a simple math problem where everything counts by tens. If you drove 1 kilometer to school, you could easily say you drove 1000 meters without having to do anything complicated. It’s as if everyone agrees to a simple rule that makes everything easier to understand, just like using a decimal system in everyday shopping!

In the English system, areas are given in square feet or square yards. The most common unit for large areas is the acre. 1 acre = 10 square chains (Gunter’s) 1 acre = 43,560 ft2 (10 x 662)

Measurements of area in the English system often use square feet or square yards, with acres being a common unit for representing larger plots of land, particularly in agriculture and real estate. One acre is defined as the area of a rectangle that is 1 chain long and 10 chains wide, which converts into a total of 43,560 square feet.

Consider a garden: if your garden is one acre, it’s about the size of a football field! When planning a community park or farm, using acres allows for easy comparisons and calculations that everyone can understand.

SI units used for finding the areas are square meter, square kilometre (km) and hectare (ha). Large tracts of land, for example, are given in hectares. Relations among them are: 1 ha = 100 m×100 m 1 ha = 1 × 104 m2 1 ha = 2.471 acres 1 square km = 1000 m×1000 m = 106 m2 1 square km = 100 ha

In the SI system, area measurements are primarily expressed in square meters, with larger areas often represented in hectares or square kilometers. A hectare is a convenient unit often used in agricultural practices, where 1 hectare equals 10,000 square meters. Understanding these relationships helps land surveyors and planners to accurately represent and use land areas.

Imagine measuring the field you want to plant. When using hectares, you’re calculating how many rows of crops will fit comfortably across that space. It’s like understanding how many plates can fit on a dinner table—knowing the area helps decide the best arrangement!

Volumes in the English system can be given in cubic feet or cubic yards. For very large volumes, for example, the quantity of water in a reservoir is designated in acre-foot. 1 acre-foot = 43,560 ft3 (area of an acre having a depth of 1ft)

In the English measurement system, volume is generally quantified in cubic feet or cubic yards, while larger volumes such as water reservoirs are often expressed in acre-feet. One acre-foot represents the volume of water that would cover one acre of land to a depth of one foot, providing a clear metric for water resource management.

Think of an acre-foot of water like a giant swimming pool filled with water sufficient to cover an entire football field to a depth of one foot. This helps understand how much water is available for usage, just like knowing how many liters are in a swimming pool helps plan for parties!

In the SI system, cubic meter (m3) is used for volume.

In the SI measurement system, volume is expressed in cubic meters. The cubic meter measurement is straightforward, reflecting the volume of a cube with one meter on each side, allowing for easy calculations in construction, space planning, and engineering.

Visualize a box that can contain 1 cubic meter of water. Knowing how many of these containers can fit into a larger space helps in transportation and storage planning, similar to your grocery shopping where you calculate how much food fits in your fridge!

The unit of angle used in surveying is the degree, defined as 1/360 of a circle. Degrees, minutes, and seconds, or the radian, are accepted SI units for angles. For measuring angles sexagesimal system is used, where: 1 circumference = 360° 1 degree = 60′ (minutes of arc) 1 minute = 60″ (seconds of arc)

Angles are measured in degrees in surveying, with a full circle divided into 360 parts. This system also incorporates subdivisions, such as minutes and seconds, to allow for precise angle measurements. In scientific contexts, radians may also be used, especially in higher mathematics and physics.

Think about navigating a car: when you turn the steering wheel, the angle you turn relates to the degrees of that turn. Just like how degrees help identify how much of a turn to take, understanding angles in surveying is crucial for mapping land and constructing buildings!

The recommended multipliers in SI units are given below: Giga unit = 1 × 10^9 units Mega unit = 1 × 10^6 units Kilo unit = 1 × 10^3 units Milli unit = 1 × 10^–3 unit Micro unit = 1 × 10^–6 unit

In the SI unit system, large and small measurements are often expressed using prefixes that indicate their scale. For example, 'kilo' represents a thousand, while 'milli' represents a thousandth. These multipliers are widely adopted for simplicity and clarity in large quantities or when dealing with very small measurements.

When measuring the distance to the nearest star, astronomers might say it's several million kilometers away—a measure you would simplify to 'mega' kilometers. Similarly, when measuring microscopic elements, terms like 'micrometers' apply. These prefixes make huge numbers easier to use, just like how abbreviations help us jot down notes quickly!

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