EC2 F2 Tipos de nivelación Nivelación Diferencial

Differential Leveling Techniques

Introduction to Differential Leveling

• Differential leveling is a topographic method used to determine the elevation difference between one or more points on the terrain.

• It can be categorized into two cases: short-distance leveling and long-distance leveling.

Short-Distance Leveling

• In short-distance leveling, the instrument (level) can see the stadia rod from a single position, allowing for direct readings of elevation differences.

• The observer can visualize numbers on the stadia rod when positioned correctly between two points (A and B).

Long-Distance Leveling

• For long distances, if there are obstructions or if the instrument cannot see the stadia rod directly, additional steps must be taken.

• If visibility is obstructed, it may require setting up intermediate points called "points of liga" to take measurements effectively.

Points of Liga and Instrument Setup

• Points of liga are established where the level instrument will be set up to take readings between distant points. Each point allows for separate measurements to calculate elevation differences accurately.

• As you move from point A to point B, positive and negative readings will occur based on how you orient your equipment during measurement sessions. This process involves changing positions frequently for accurate data collection.

Calculating Elevation Differences

• Elevation differences can be calculated using two methods:

• The sum of positive readings minus negative readings.

• The difference in elevations between two points (Elevation at B minus Elevation at A).

Data Collection Process

• During fieldwork, a table is created that includes observed points, positive/negative readings, and corresponding elevations; this data is essential for later calculations in an office setting (referred to as "gabinete").

• Arbitrary elevations may also be used; these are not officially referenced but can still serve practical purposes in certain projects. An example would include using arbitrary values like 100 meters without official reference levels.

Example Measurement Procedure

• In practice, while measuring:

• Positive readings indicate an increase in elevation towards point A.

• Negative readings indicate a decrease towards point B.

Understanding Instrument Elevation Calculations

Elevation Calculation Methodology

• The elevation of the instrument is marked, and the negative reading from the next line is subtracted to determine the elevation of point B. This process illustrates how negative readings are utilized in calculations.

• When multiple points are involved, the same method applies. For example, starting with an elevation of 100 at point A and adding a positive reading of 1.836 results in an elevation of 101.836 for point B.

• The height of the instrument is crucial; subtracting the next negative reading from this height gives the elevation for subsequent points, confirming that point B's calculated elevation is 101.141 meters.

• To calculate differences in elevations (denivel), one can use either method: summing positive readings minus negative readings or directly calculating by subtracting elevations between two points.

• Both methods yield consistent results; for instance, using either approach confirms that the difference in elevations between points A and B equals 1.141 meters.

Practical Application and Example

• An exercise involves completing a table to determine denivel based on field data collected during differential leveling across multiple points.

• The provided example includes observed points, back readings, instrument heights, forward readings, and corresponding elevations—essentially what needs to be measured in the field.

• Empty spaces in calculations indicate where no data exists; these should be canceled out when performing summations or calculations.

• To compute values accurately, it’s essential to consider that instruments are placed between two points rather than directly on them; thus adjustments must be made accordingly.

• The calculation begins with determining instrument height at Point A plus back readings (positive), leading to an initial value used for further computations regarding Point B's elevation.

Continuing Calculations

• For Point B's elevation calculation: start with an initial value (e.g., 101.652), then subtract any forward reading (negative), resulting in a new calculated height for subsequent evaluations.

• As calculations progress through various points (like Liga 2), each step involves taking previous heights and adjusting them based on forward readings until all necessary values are derived systematically.

• Each new calculation builds upon prior results; for instance, if you have a previous height of 100.829 plus a forward reading leads to another adjusted height needed for future steps.

• Consistency is key throughout these calculations as they rely heavily on accurate subtraction of forward readings from previously established heights to maintain integrity across all measurements taken during leveling exercises.

Understanding Elevation Differences

Key Concepts of Elevation and Results

• The discussion begins with a prompt for questions regarding the exercise, indicating that the results obtained are negative. This negativity suggests a difference in elevation between two points.

• Two points, referred to as A and B, can yield either positive or negative results based on their elevations. A positive result indicates point B is higher than point A.

• If the result is negative, it implies that point A is at a higher elevation compared to point B. The speaker clarifies this by referencing specific values: Point A has a value of 100 while Point B has 99.

• The importance of notation is emphasized; stating "elevation AB" differs from "elevation BA," which can lead to different interpretations of height differences.

• The order of letters in denoting points significantly affects interpretation. For example, if "AB" is used positively, it means B is lower than A; conversely, if "BA" is used positively, then A is lower than B.

Clarifications on Notation and Interpretation

• It’s crucial to maintain clarity in notation since changing the sign alters the meaning of the results. Different notations may yield identical numerical values but convey opposite meanings depending on how they are presented.