1.22.5 - Triangulation survey work
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Field Work in Triangulation Surveys
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Today, we will explore the fieldwork involved in triangulation surveys. What do you think is the first step we need to take?
Is it to perform a reconnaissance survey?
Absolutely! The reconnaissance survey helps us examine the terrain and select suitable positions for baselines and triangulation stations. It's vital for proper planning. Can anyone name another step in the fieldwork?
Erecting signals for visibility?
Correct! Erecting signals allows for clear visibility between stations. Remember, visibility is crucial in triangulation. What follows after erecting signals?
Measuring the baseline?
Yes! After that, we proceed with measuring the horizontal and vertical angles. Let's recap: reconnaissance survey, signal erection, baseline measurement, and measuring angles. Good job, everyone!
Computational Work in Triangulation Surveys
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Now that we've covered fieldwork, let’s dive into computational work. Why do you think checking observed angles is significant?
To ensure our measurements are accurate?
Exactly! Checking observed angles helps identify any errors. What about triangulation errors? Why do we check those?
To minimize mistakes in our calculations?
Exactly! We need to ensure reliability in our results. Finally, we also compute the latitude and departure of each side in our triangulation network. Who can summarize the computational steps for me?
Checking angles, checking triangulation errors, computing the corrected length of the baseline, and calculating latitudes and departures.
Perfect summary! Accuracy is key in triangulation surveys.
Importance of Triangulation in Surveys
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What are some applications of triangulation surveys that we discussed in the previous chapters?
They can help establish control points for geodetic surveys!
Yes! Also, triangulation helps in determining accurate locations for civil engineering works like bridges and tunnels. Why else is triangulation preferred?
Because it reduces errors in measurement.
Exactly! Through triangulation, we can mitigate the accumulation of errors we often see in other surveying methods. Remember the key benefits of triangulation when applying it in various surveys.
Introduction & Overview
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Quick Overview
Standard
Triangulation survey work consists of fieldwork, which includes several stages from reconnaissance to measurement of angles, and computational work that verifies observations and calculates various triangulation components. The section emphasizes the importance of accuracy and thoroughness in both steps to ensure reliable survey results.
Detailed
Triangulation Survey Work
Triangulation survey work is a systematic method for establishing points in a geographic area using geometrical triangulation methods. It is segmented into two major parts: Field Work and Computational Work.
Field Work
The fieldwork includes crucial stages such as conducting a reconnaissance survey to examine the terrain and choose appropriate baseline and triangulation station locations, erecting signals for visibility, measuring the starting baseline, measuring horizontal and vertical angles, and concluding with a measurement of the closing baseline. Each of these steps plays a vital role in the overall survey process.
Computational Work
Computational work follows the fieldwork and involves verifying the observed angles, assessing triangulation errors, checking the closing horizon error, calculating the corrected baseline, computing triangle side lengths, and determining the latitude and departures of each side within the triangulation network. Overall, the precision in both the field and computational stages is essential to ensure that triangulation surveys yield accurate and reliable data.
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Overview of Triangulation Survey Work
Chapter 1 of 4
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Chapter Content
It involves two major steps; (i) Field work, and (ii) Computational work.
Detailed Explanation
Triangulation survey work is divided into two primary phases: field work and computational work. The field work encompasses the actual practice of surveying on-site, while the computational work involves processing the collected data to produce usable results.
Examples & Analogies
Think of the field work like taking measurements while building a house—you're checking dimensions and making sure everything is in the right place. The computational work is akin to drafting the blueprints based on those measurements to ensure that you have a clear plan moving forward.
Field Work Steps
Chapter 2 of 4
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Chapter Content
The field work involves (a) Reconnaissance survey, (b) Erection of signals, (c) Measurement of starting baseline, (d) Measurement of horizontal and vertical angles, (e) Observations to determine the azimuth of sides, and (f) Measurement of closing baseline.
Detailed Explanation
The field work consists of several key activities: 1. A reconnaissance survey helps in understanding the area better and planning the triangulation layout. 2. Erection of signals marks the locations for observation. 3. Measuring the starting baseline is critical as it forms the basis for triangulation. 4. Measuring horizontal and vertical angles allows for the precise calculation of positions. 5. Observations to determine the azimuth are necessary to know the direction of the sides of triangles formed. 6. Finally, the closing baseline is measured to check accuracy and ensure all points are connected properly.
Examples & Analogies
Imagine planning a treasure hunt in a park. First, you would walk around to see where to hide clues (reconnaissance survey). Next, you mark the spots where the treasure is hidden with flags (signals), then you would start measuring distances from point to point (baseline), observing directions (angles), and finally ensuring you can get back to the starting point to verify you haven't got lost (closing baseline).
Computational Work Procedures
Chapter 3 of 4
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Chapter Content
The computational work includes: • Checking the observed angles • Checking the triangulation errors • Checking the closing horizon error at each station (i.e., sum = 3600) • Computation of corrected length of baseline • Computation of sides of triangles • Computation of the latitude and departure of each side of the triangulation network, and • Computation of independent coordinates of the triangulation stations.
Detailed Explanation
In the computational stage, the first step is to check the angles observed during the measurements to confirm their accuracy. Next, any errors found in the triangulation process need to be accounted for and corrected. Each station should also indicate a total horizon error of 360°, ensuring the angles form a closed loop. Following this, the length of the baseline is corrected to reflect actual measurements, which leads to calculating the lengths of triangle sides, as well as the latitude and departure for each side. Finally, independent coordinates of all triangulation stations are computed to determine their exact locations.
Examples & Analogies
This stage is comparable to a chef checking the recipe after a meal is prepared (checking angles) to ensure everything was measured correctly. They might taste the dish (checking errors) and adjust ingredients accordingly (correcting baselines). Before serving, they ensure all flavors blend well together (checking closing error), and finally, they record which ingredients and quantities were used (calculating coordinates).
Reconnaissance Survey Importance
Chapter 4 of 4
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Chapter Content
The reconnaissance of the area involves; (i) proper examination of the terrain, (ii) selection of suitable positions for baselines, (iii) selection of suitable positions of triangulation stations, and (iv) determination of intervisibility of triangulation stations.
Detailed Explanation
During reconnaissance, surveyors examine the landscape to understand its features, which helps in determining the best locations for baselines and triangulation stations. It is crucial for the bases to be visible from one another; this is known as intervisibility. Each of these actions ensures that the survey can be conducted accurately.
Examples & Analogies
This process can be likened to planning a hiking route. Before starting, hikers will look at maps and the terrain (examining the landscape) to choose the best trails (selecting positions). They will also ensure that the next point on the trail is visible from the current point (intervisibility), to avoid getting lost.
Key Concepts
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Field Work: The initial phase involving reconnaissance, signal erection, and measurements.
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Computational Work: Following observations, computations and checks to ensure accuracy.
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Triangulation Importance: Critical for accurate survey results in civil engineering and geodetic surveys.
Examples & Applications
In a triangulation survey, fieldwork involved selecting three triangulation stations and measuring the baseline length, followed by angles to later compute the positions of new points.
Computationally, if the closing horizon error measured at the station equals 3600, the measurements are considered accurate and reliable.
Memory Aids
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Rhymes
In triangulation, start with a view, check your angles, it’s what we do.
Stories
Imagine a team of surveyors who first scout the land, set up their flags high, and measure angles just right, ensuring every triangle holds firm before they finish setting their map.
Memory Tools
Remember 'F-C-C' for Field - Compute - Check to secure your triangulated results.
Acronyms
F.C.C. stands for Field work, Computational work, and Corrections for triangulation accuracy.
Flash Cards
Glossary
- Triangulation
A surveying method using triangles to establish accurate control points based on known distances and angles.
- Baseline
A measured line in triangulation from which other distances and angles are computed.
- Reconnaissance Survey
A preliminary survey to assess the area and determine locations for triangulation stations.
- Triangulation Station
Specific points marked on the ground used as vertices in triangulation.
- Computational Work
The phase where observed data are processed, checked for accuracy, and computations made to derive triangulation results.
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