Control and Cadastral Surveys Flashcards

A surveyor needs to restore a lost interior section corner (a corner common to four sections) within the Public Land Survey System (PLSS). The original monument and its accessories are obliterated, but the four nearest quarter corners located to the north, south, east, and west are recovered and verified. Which of the following methods is the standard procedure for reestablishing the lost corner's position?

Answer: Double proportionate measurement from the four found quarter corners.

Double proportionate measurement is the standard method prescribed by the Bureau of Land Management (BLM) for restoring a lost corner common to four townships or four sections. [8, 26] It involves a proportionate measurement on the meridional line between the nearest found corners north and south to determine the latitude of the lost corner, and a separate proportionate measurement on the latitudinal line between the nearest found corners east and west to determine its longitude. The intersection of these two lines reestablishes the corner's position. [4, 21]

Which of the following describes the standard procedure for the legal subdivision of a regular section within the Public Land Survey System (PLSS) to locate its geographic center, known as the center quarter-corner?

Answer: Connecting the opposing quarter-section corners with straight lines and establishing the center at their intersection.

The legal center of a regular section is determined by the intersection of straight lines drawn between the opposing quarter-section corners. Specifically, a line is run from the north quarter-corner to the south quarter-corner, and another line is run from the east quarter-corner to the west quarter-corner. The point where these two lines cross is the legally recognized center quarter-corner of the section. [16]

In establishing a high-precision horizontal control network, a surveyor includes numerous redundant measurements, such as observing all angles in a quadrilateral and both of its diagonals. What is the primary benefit of incorporating this redundancy into the survey?

Answer: It allows for a rigorous statistical analysis and least-squares adjustment to increase overall accuracy.

Redundant measurements are essential for a robust control survey because they provide more data than is minimally required to determine the positions of the points. [12, 13] This over-determination allows for a least-squares adjustment, which is a statistical method that analyzes the measurements, distributes random errors, helps detect blunders, and computes the most probable coordinate values for the network stations, thereby increasing the overall precision and reliability of the survey. [19, 22]

What is the primary function of a Standard Parallel, also known as a correction line, within the framework of the Public Land Survey System (PLSS)?

Answer: To correct for the convergence of meridians and maintain the rectangular nature of the system.

Due to the curvature of the Earth, north-south lines (meridians) converge as they approach the poles. Standard Parallels are true east-west lines established at regular intervals (typically every 24 miles) to correct for this convergence. [2, 17] At each Standard Parallel, the range lines are reset to their proper six-mile spacing, which keeps the resulting townships as close to their intended six-by-six-mile square shape as possible. [28]

A surveyor is working along the northern boundary of a township and finds two sets of monuments at a section line intersection. One monument is identified as the 'standard corner' on the standard parallel, and a second monument, located slightly to the east, is identified as the 'closing corner' for the section line run from the south. What is the significance of this 'closing corner'?

Answer: It marks the intersection of a newly surveyed line with a previously established line, accounting for convergence.

In the PLSS, a closing corner is established when a survey line, such as a township or section line, intersects a previously established boundary like a standard parallel. [23] Because range lines converge towards the north, the line surveyed from the south will not typically intersect the standard parallel at the location of the standard corner already set on that line. The closing corner is monumented at the actual point of intersection, and the distance between the closing corner and the standard corner is recorded in the field notes. [3, 20]

When a surveying organization submits geodetic control survey data to the National Geodetic Survey (NGS) for inclusion in the National Spatial Reference System (NSRS), the data must be formatted according to a specific set of guidelines. What is this formal process and its associated user guide commonly called?

Answer: Bluebooking

The term 'Bluebooking' refers to the process of preparing and submitting geodetic data to the NGS in the standard format required for inclusion in the NSRS. The name comes from the user's guide, officially titled 'Input Formats and Specifications of the National Geodetic Survey Data Base,' which was historically published with a blue cover. [7, 11] This process ensures that submitted data is complete, properly described, and meets the accuracy standards necessary for the national database. [14]