Presented by Dane Courville, PLS
Session Materials
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Meeting summary for Mentoring Mondays for the Land Surveying Profession (04/28/2025)
Quick recap
Dane presented a new presentation on one-point, two-point, and three-point problems in surveying, aiming to fine-tune his understanding of the topic. The team discussed various methods for determining lost corners in land surveying, including the use of trigonometry, two-point control, three-point control, and single proportioning. The conversation also touched on the importance of understanding coordinate systems, the history and pass rates of surveying exams, and the potential requirement for survey crew members to have LSIT certification on certain city projects in Southern California.
Next steps
- Dane: Update the presentation to include a caveat about the rotation between assumed and true coordinates when using cardinal equivalents
- Rob: Continue discussions with Southern California city regarding LSIT requirements for survey crew members
- Rob: Continue working with company to connect employees with Dane’s program for LSIT preparation
- Dane: Present the tech track at the upcoming Arizona-New Mexico Conference
- Jerry: Follow up with Mike regarding the latitude and longitude spreadsheet discussion
- Trent: Share the presentation PDF in Dropbox and on the website for all attendees to access
- Trent: Share Jerry’s diagram for lost corners in the Dropbox folder for future reference
- Trent: Forward Mike’s email contact information to Jerry
- Trent: Share the 2005 California PLS exam materials with Dane and Kyle Brooks
- Dane: Review the shared 2005 California exam materials for exam preparation purposes
Summary
Surveying Problems: One-Point, Two-Point, Three-Point
Dane introduces a new presentation on one-point, two-point, and three-point problems in surveying. He explains that this topic has been a point of confusion for him and his colleagues, which prompted him to create this presentation to fine-tune his understanding. Dane plans to cover all three types of problems, starting with one-point problems. The presentation is being shared for the first time, and Dane acknowledges that he may need to refine it further. Trent mentions that this is the 150th episode of Mentoring Mondays, and the presentation PDF is being shared with attendees.
1 Point Control Method in Surveying
Dane discussed the use of 1 point control method in surveying, emphasizing that it should only be used when all other evidence is unavailable. He explained that this method is used when only one direction (north, south, east, or west) has usable information, while the other three directions lack any bearings or distances. Dane stressed that this method should not be the first choice and should only be used when all other methods fail. He also highlighted the importance of understanding right triangles and proportioning in surveying operations.
Calculating Lost Corner Latitude and Departure
Dane explained the process of using trigonometry to calculate the latitude and departure of a lost corner in a survey. He demonstrated how to use the angle and hypotenuse length to determine the latitude and departure values, and how to use these values to calculate the position of the lost corner. He also discussed how to handle situations where the lost corner is located in a different direction. The team was able to follow along and understand the process.
Latitude and Departure Value Process
Dane explained the process of finding latitude and departure values, and how to use them to determine the location of a lost corner. He emphasized the importance of understanding the orientation of the situation, as it affects whether to add or subtract values. Dane also discussed the concept of 2-point control, where two known points are used to generate a lost corner. He noted that this situation is better than having only one known point, but still not ideal. Trent added that declination based on position at the time of the original survey could affect the calculations. Dane also mentioned the possibility of using a 3-point method if a monument is found before reaching the township line.
Two-Point Control for Township Information
Dane discussed the process of using two-point control to generate information within a township. He explained that a township acts as a unit and that information from all townships is used to generate a position. Dane also clarified that a township is a barrier that cannot be crossed to help generate information within it. He demonstrated how to use two-point control to generate a lost corner, emphasizing the importance of understanding the positive and negative directions in the process. Dane also provided a chart to help organize the information needed for the two-point control method.
Three-Point Control in Land Surveying
Dane explains the concept of three-point control for determining lost corners in land surveying. He describes it as a combination of single proportioning and one-point control. The process involves first single proportioning along one line where two opposing known points are available, then using one-point control for the other direction. Dane emphasizes that this method is more mathematically accurate than one-point or two-point control, but still not ideal. He provides examples of scenarios where three-point control might be used, such as for a lost section corner on a township line with three known quarter corners.
Single Proportioning for Lost Corner
Dane explains the process of single proportioning to locate a lost corner using known points and record information. He describes a step-by-step approach, starting with calculating latitudes for north and south lines to determine the total latitudinal distance per record. This is followed by measuring the actual distance in the field. Dane then uses a matrix to solve for the measured proportional distance, which helps determine the northing of the lost corner. He emphasizes that this method can be applied to both north-south and east-west orientations. Finally, Dane explains how to calculate the easting of the lost corner using departure values, resulting in the complete coordinates of the lost point.
Index Correction in BLM Manual
Dane’s phone died during the meeting, causing a brief interruption. Dane then discussed the concept of index correction in the BLM manual, which allows surveyors to make subjective decisions based on their observations rather than strictly following mathematical operations. The team agreed that they had not encountered such extreme methods in their work. Trent then proposed to discuss the 2005 California PL&S exam state-specific exam before the conversation ended.
Compensating for Convergence in Grid Systems
Jerry explains that when working with grid systems, it’s crucial to compensate for the convergence between the assumed and true meridians. He cautions that simply adding latitude and departure components to assumed coordinates may not accurately represent the original system. Dane acknowledges the importance of this point and agrees to add a caveat to his presentation. Jerry further discusses the complexities of varying bearings along lines and the challenges of working with Wisconsin plats that lack record directions. The conversation highlights the intricacies of surveying and the need for careful consideration of coordinate systems and bearings.
Survey Exam Pass Rates and LSIT
The group discusses the history and pass rates of surveying exams, particularly in California. Steven recalls that in the late 1990s, there was a year when only 9 people passed the exam, leading to complaints about its difficulty. In 2005, the entire exam was released, allowing people to see it was fair and doable. Rob mentions that this release enabled CLSA chapters to create more effective exam review classes, which helped increase pass rates from around 10% to 21-25%. The conversation then shifts to current exam pass rates and the potential requirement for survey crew members to have LSIT certification on certain city projects in Southern California.
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