Land Surveyor Interview Questions (GPS & Topography)

Before the First Stake

Land surveyor interview questions are built to find out if you can be accurate in the real world, not just in perfect conditions. You might be working in tall grass, near traffic, or on a site where the “corner” is buried under decades of stories and assumptions.

Hiring managers look for someone who can collect clean data, document decisions, and explain boundary logic without drama. They want to hear how you set control, check your setup, and handle conflicting evidence without creating a legal mess.

This guide leans into the practical side of geomatics: instruments, coordinate systems, and field judgment. Use it to show you can measure carefully, process data responsibly, and communicate results that contractors, owners, and inspectors can rely on.

Geodesy & Coordinate Systems

Q: Explain the difference between the Geoid, the Ellipsoid, and Orthometric Height.

This is the most critical concept for modern GPS surveying. The Ellipsoid is a smooth, mathematical model of the earth (like the WGS84 or GRS80) used by GPS satellites to calculate height ($$h$$). However, the earth is not smooth; gravity varies due to density. The Geoid is the equipotential surface that represents “Mean Sea Level” – where water would settle if stopped by nothing but gravity.

Orthometric Height ($$H$$) is what we traditionally call “elevation” above sea level. The relationship is $$H = h – N$$, where $$N$$ is the Geoid Height (separation). GPS natively measures Ellipsoid height. To get a useful elevation for construction (water flow), we must apply a Geoid Model (like GEOID18). Failing to apply the correct geoid model can result in elevation errors of 30 meters or more, which is catastrophic for drainage design.

Q: Describe the “Hierarchy of Evidence” in boundary surveying.

When retracing a property line, evidence often conflicts (e.g., the deed says 100 feet, but the monuments are 101 feet apart). The legal hierarchy generally dictates the order of importance:
1. Senior Rights: The chronological sequence of conveyance. You cannot sell what you do not own.
2. Call for Natural Monuments: Rivers, trees, rocks (unlikely to move).
3. Call for Artificial Monuments: Iron pins, concrete posts set by original surveyor.
4. Call for Adjoiners: “To the land of Smith.”
5. Courses and Distances: Bearings and lengths.
6. Area: “10 Acres” is the least reliable indicator.
As a surveyor, I prioritize finding the original monuments over strictly following the math in the deed descriptions.

Q: What is the difference between “Grid” and “Ground” distances?

State Plane Coordinate Systems project the curved earth onto a flat mapping plane (Grid). Because of this projection, distances are distorted. A Grid Distance is the length measured on this flat mathematical plane. A Ground Distance is what you actually measure with your tape or Total Station on the surface of the earth.

The relationship is defined by the Combined Scale Factor (CSF): $$Ground = Grid / CSF$$. In high-elevation areas or large highway projects, the difference can be significant (e.g., 0.5 feet per mile). Construction layout must be done in Ground coordinates because a contractor’s tape measure reads Ground distances. Mixing these up leads to “short” buildings or bridges that don’t fit.

Q: How do you perform a “Two-Peg Test” (Collimation Test) on an automatic level?

The Two-Peg Test checks if the level’s line of sight is truly horizontal.
1. Set two pegs (A and B) about 200 feet apart.
2. Set the level exactly midway between them. Read rod A ($$a_1$$) and rod B ($$b_1$$). The difference ($$a_1 – b_1$$) is the true elevation difference because any error cancels out due to equal distances.
3. Move the level very close to peg A. Read rod A ($$a_2$$) and rod B ($$b_2$$).
4. Calculate the new difference ($$a_2 – b_2$$).
5. Compare the two differences. If they vary significantly (e.g., >0.005 ft), the crosshair needs adjustment. I perform this test weekly or after any rough transport of the instrument.

Field Techniques & Technology

Field Scenarios & Problem Solving

You are running a boundary survey and find an existing iron pin that is 0.5 feet off from your calculated deed position. Do you hold it or set a new one?

The contractor calls you angrily saying your column grid layout is “wrong” because it doesn’t match his tape measure.

You are midway through a traverse loop and the battery dies, or the weather turns severe. What do you do?

Advanced Legal & Computational Topics

Q: Explain “Adverse Possession” and your role in it.

Adverse Possession is a legal doctrine where a trespasser can gain title to land if they occupy it openly, notoriously, exclusively, and continuously for a statutory period (e.g., 10-20 years). As a surveyor, I do not decide adverse possession; only a judge can do that. My role is to locate the evidence of occupation.

If I see a fence line that is 5 feet over the deed line, I locate both the deed line and the fence. I show the encroachment clearly on the plat. I might note “Fence is 5′ North of Boundary Line.” I inform my client of the discrepancy, but I never tell them “You own up to the fence.” That is legal advice, which is outside my scope of practice.

Q: What is Least Squares Adjustment?

Least Squares is a statistical method used to adjust survey networks. Unlike the Compass Rule (which is a simple geometric average), Least Squares weights the observations based on their estimated quality. I can tell the software, “I trust my distances more than my angles” or “This GPS baseline is less precise than that Total Station shot.”

The algorithm minimizes the sum of the squares of the residuals (errors). It provides error ellipses for every point, telling me exactly how confident I can be in that coordinate (e.g., “Point 100 is accurate to +/- 0.02 ft at 95% confidence”). It is essential for high-precision geodetic control networks.

Q: How do you handle “Multipath” in GPS surveying?

Multipath occurs when the satellite signal bounces off a reflective surface (building, metal fence, water) before hitting the antenna. This delays the signal, causing the receiver to calculate a longer distance, resulting in a bad position solution (often moving wildly). To mitigate this, I use a Mask Angle (e.g., 15 degrees) to ignore low-horizon satellites. I avoid setting points right next to tall glass buildings. If I must shoot there, I increase the observation time (averaging out the noise) or switch to a Total Station for that specific area.

Q: Describe the Public Land Survey System (PLSS).

The PLSS (Sectional Systems) divides land into Townships and Ranges. A standard Township is 6 miles by 6 miles, containing 36 Sections (each 1 mile square, 640 acres). Descriptions look like “NW 1/4 of Section 12, T2N, R3E.” As a surveyor, I must know how to “break down a section” – finding the section corners and quarter-corners to subdivide the land legally. I understand the history of the GLO (General Land Office) surveys and how to handle the convergence of meridians (why sections aren’t perfectly square).

Land Surveyor Knowledge Check

❓ FAQ

Measure Carefully, Explain Clearly

When you study from this interview question hub, practice explaining your decisions, not just your tools. The interview is as much about judgment as it is about equipment.

Be ready to describe how you set control, verify backsights, and document boundary evidence. If you can communicate that calmly and precisely, you will stand out as the person who keeps projects and property lines out of trouble.