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Interactive Audio Lesson
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Understanding EDM and Height Corrections
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Today, we'll look at a practical problem involving Electronic Distance Measurement, or EDM. Who can tell me the basic principle of how EDM operates?
EDM measures the distance by calculating the time it takes for a signal to travel to a target and back.
Exactly! And we also need to consider the instrument's height. Why do you think height matters?
Because it can affect the true distance if we don't correct for it!
Right! The height of the EDM and the reflector above the ground must be accounted for in our calculations. Can anyone share how we find the horizontal distance?
We need to use trigonometry based on the vertical angle!
Correct! Remember to keep your triangle definitions in mind, particularly how they relate to the angle of elevation. Let's summarize: When measuring, always adjust for equipment height and apply trigonometric principles for accuracy.
Calculation of Horizontal Distance
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Now, let's dive into the actual problem. We have a total measured distance of 714.652 m. Who remembers how to apply height corrections here?
We need to deduct the heights of the EDM and the reflector because we want the horizontal length.
Exactly! Good job! Now, we also need to deal with the vertical angle of +4°25′15″. How does this fit into our calculations?
We'll use the tangent function because we need to find the opposite side in relation to our angle.
You're on the right track! By calculating the horizontal distance using the cosine of the angle, we can effectively find the length. So, to summarize, we first adjust our measured distance, then apply our angle to get the horizontal measurement.
Introduction & Overview
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Quick Overview
Standard
An unsolved numerical question involves calculating the horizontal length of a line measured with an EDM along a slope and corrected for various factors using a theodolite for vertical angle measurement. The exercise tests knowledge of geometric relationships and measurement corrections.
Detailed
In this section, we are presented with a numerical problem that requires understanding of distance measurement techniques. The example outlines a scenario where a distance is measured along a slope using an Electronic Distance Measurement (EDM) instrument. The measured distance must be corrected for the height of the instrument and the reflector above ground, as well as the vertical angle measured to the target. The key approach to solve this problem involves applying trigonometric principles and geometric relations to derive the horizontal length of the line in question. Understanding how to incorporate corrections for atmospheric conditions and equipment constants is critical in achieving accurate results. This section emphasizes the practical application of surveying principles to real-world measurement situations.
Audio Book
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Introduction to the Problem
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A distance is measured along a slope with an EDM which when corrected for
meteorological conditions and instrument constants, is 714.652 m. The EDM is 1.750 m above
the ground, and the reflector is located 1.922 m above ground.
Detailed Explanation
This first part of the problem is setting up the scenario for a distance measurement using an EDM (Electronic Distance Measurement) device. Here, the distance measured along a slope is stated as 714.652 meters. It's important to note that this measurement is corrected for meteorological conditions and instrument constants, which makes it usable for further calculations. The heights of both the EDM and the reflector above the ground are also given, which will be critical in the next steps of solving for the horizontal length.
Examples & Analogies
Imagine you are on a hill and you want to measure the distance to a tree below. Using a tool similar to an EDM, you can determine the distance to the base of the tree. However, you also need to consider how high you are above the ground and the height of the tree itself, much like the way we need the heights above ground here to understand the real distance to the ground point.
Vertical Angle Measurement
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A theodolite is used to measure a vertical angle of +4°25′15″ to a target placed 1.646 m above ground.
Detailed Explanation
This chunk introduces the use of a theodolite, an instrument used for measuring vertical and horizontal angles. The vertical angle measured is +4°25′15″, meaning the target is elevated slightly above the horizontal line of sight of the instrument. The height of the target is specified as 1.646 meters above the ground. This angle will help us determine how much the line of sight deviates from a straight path horizontally, which is essential for calculating the effective horizontal distance.
Examples & Analogies
Consider you are aiming a laser pointer at a balloon hanging above you. As you tilt your laser pointer up toward the balloon, you create an angle with the horizontal line from your pointer to the ground. The vertical angle tells you how 'steep' your pointer needs to be aimed to hit the balloon.
Calculating Horizontal Length
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Determine the horizontal length of the line. (Ans: 712.512 m)
Detailed Explanation
This final chunk poses the question that needs to be solved using the given measurements. To find the horizontal length of the line, we apply trigonometric concepts. The measured distance (714.652 m) represents the hypotenuse of a right triangle, where one leg is the horizontal distance we are trying to find, and the other leg accounts for the height difference between the EDM, the reflector, and the target. The vertical angle and the known heights are key to setting up this calculation, and using the sine and cosine functions appropriately will yield the horizontal length.
Examples & Analogies
Think of this process like using a ladder to reach a high window. The ladder (like the measured distance) forms a triangle with the ground. The base of the wall (horizontal distance) and how high you reach (the vertical distance) create two sides of a triangle. By knowing how long your ladder is and the angle it rests at, you can figure out how far away from the wall the base of the ladder is.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Height Corrections: Adjusting measurements based on the height of the instrument and target.
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Trigonometry in Measurement: Using sine, cosine, and tangent ratios to solve for distances.
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Horizontal vs. Slope Distance: Understanding the difference and why corrections are necessary.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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When you measure 500 m up a hill with the EDM from a height of 1.5 m, to find the horizontal distance, you’ll need to apply height corrections.
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In a scenario measuring a vertical angle of 30 degrees, you can use the cosine function to determine how much distance is 'lost' due to the angle.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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To find the length that's straight, cosine helps us relate.
📖 Fascinating Stories
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Imagine hiking up a slope, you measure and hope. But first, correct for height, then find your way with trigonometric might.
🧠 Other Memory Gems
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H.A.T. stands for Height, Angle, and Trigonometry - the key to finding true distance!
🎯 Super Acronyms
H.E.A.D. - Height, EDM, Angle, Distance - Remember these four for sonic precision!
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: EDM (Electronic Distance Measurement)
Definition:
An electronic device used to measure distances by transmitting a signal to a target and back.
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Term: Theodolite
Definition:
A surveying instrument for measuring horizontal and vertical angles.
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Term: Vertical Angle
Definition:
The angle measured with respect to a horizontal plane, indicating the height of an object.
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Term: Slope Distance
Definition:
The distance measured along a slope which requires correction to obtain horizontal distance.
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Term: Horizontal Length
Definition:
The straight line distance on a horizontal plane, typically found using trigonometric calculations.