GELE Reviewer 2026

Answer: B. The equipotential surface of Earth's gravity field that best fits global mean sea level

Step 1: Recall the three surfaces in geodesy — ellipsoid, geoid, and terrain. Step 2: The ellipsoid is a purely mathematical surface (e.g., WGS84, PRS92). Step 3: The terrain is the physical ground surface. Step 4: The geoid is defined by gravity — specifically, it is the equipotential surface of Earth's gravity field that coincides with mean sea level worldwide. Step 5: Options A and D describe the ellipsoid; Option C describes the terrain. Only Option B correctly defines the geoid.

Answer: A. To represent the curved surface of the Earth on a flat plane

Step 1: Recall the core problem in cartography — the Earth is an oblate spheroid (3D), but maps are flat (2D). Step 2: A map projection is a systematic mathematical transformation that 'flattens' the curved surface onto a developable plane. Step 3: Option A is correct — this is the defining purpose of any projection. Step 4: Option B is wrong because distortion is unavoidable; every flat map distorts something (area, shape, distance, or direction). Step 5: Options C and D describe other geodetic operations, not the definition of a map projection.

Answer: B. Cadastral survey

Step 1 – Recall the definition: A cadastral survey is a systematic, government-initiated survey of every parcel within a defined area (municipality or city). Step 2 – Distinguish from other types: An isolated survey covers only a single lot; a mineral survey is for mining claims; a relocation survey re-establishes existing boundaries. Step 3 – Key word: 'ALL parcels' is the defining characteristic of a cadastral survey. Step 4 – Legal anchor: Under CA 141 (Public Land Act) and implemented by DENR-LMB, cadastral surveys are conducted to support the Torrens registration system. Conclusion: The answer is 'Cadastral survey.'

Answer: C. Blunder (mistake)

Step 1: Recall the three categories of errors in surveying — blunders, systematic errors, and random errors. Step 2: A blunder is a gross mistake caused by carelessness, inattention, or misreading an instrument. Step 3: Misreading a tape by 5 m is far too large to be a random or systematic error; it is clearly a careless mistake. Step 4: Random errors are small and unpredictable; systematic errors follow a definable pattern. Neither fits here. Step 5: Therefore, the correct classification is a blunder, which must be detected and eliminated before any adjustment is performed.

Answer: C. h = H + N

Step 1: The three heights in geodesy are measured from different reference surfaces. Step 2: h (ellipsoidal height) is measured from the ellipsoid upward to the point. Step 3: N (geoid undulation) is the height of the geoid above the ellipsoid. Step 4: H (orthometric height) is measured from the geoid upward to the point. Step 5: Geometrically, h = H + N because the ellipsoidal height equals the orthometric height plus the height of the geoid above the ellipsoid. Rearranging gives H = h − N, which is the working formula for GNSS-to-elevation conversion.

Answer: B. Conformal (orthomorphic) projection

Step 1: The key term is 'preserves angles and local shape.' Step 2: Conformal (also called orthomorphic) projections maintain angular relationships at every point, meaning a small circle on the ellipsoid plots as a small circle on the map. Step 3: Equal-area projections preserve area, not angles — they are the opposite property. Step 4: Equidistant projections preserve distance only along certain lines, not angles. Step 5: Azimuthal refers to a type of developable surface (planar), not a preserved property — an azimuthal projection can be conformal, equal-area, or equidistant.

Answer: C. Isolated (individual) survey

Step 1 – Identify the scope: Only one (1) lot is involved. Step 2 – Apply the definition: An isolated or individual survey surveys a single parcel for titling, transfer, or development purposes. Step 3 – Eliminate wrong options: A cadastral survey involves all parcels in a locality — far broader than one lot. A public-land survey applies to alienable/disposable lands. A mineral survey is for mining areas. Step 4 – Remember: Even though it covers one lot, the isolated survey must still be tied to existing geodetic control (BLLM) on PRS92. Conclusion: 'Isolated (individual) survey' is the correct answer.

Answer: C. Random (accidental) errors

Step 1: Blunders must be detected and removed before any adjustment is attempted — least squares cannot handle them. Step 2: Systematic errors must be modeled and corrected through calibration or mathematical corrections before adjustment. Step 3: Random (accidental) errors are small, vary in sign, and follow the normal (Gaussian) distribution. They are unavoidable. Step 4: Least squares adjustment is specifically designed to distribute random errors optimally among all observations. Step 5: Therefore, only random errors are addressed by adjustment computations such as least squares.

Answer: C. Ellipsoidal height (h)

Step 1: GNSS (e.g., GPS, GLONASS, Galileo) computes positions using satellite ranging referenced to a mathematical ellipsoid (WGS84 globally; PRS92 for the Philippines). Step 2: The height component output by GNSS processing is therefore the ellipsoidal height h — the vertical distance from the ellipsoidal surface to the point. Step 3: Orthometric height H (the engineering 'elevation above MSL') requires a geoid model to convert from h using H = h − N. Step 4: Dynamic heights and geopotential numbers are derived from spirit leveling plus gravity observations — not directly from GNSS. Step 5: Always remember: raw GNSS height ≠ usable elevation without a geoid model.

Answer: B. 9 996.00 m

Step 1: Recall the formula: grid distance = k × ellipsoidal distance. Step 2: Substitute values: grid distance = 0.99960 × 10 000.00 m. Step 3: Compute: 0.99960 × 10 000.00 = 9 996.00 m. Step 4: Since k < 1, the grid distance is shorter than the ellipsoidal distance — this is expected near the central meridian of a Transverse Mercator projection. Step 5: Option A (10 004.00 m) would result from k > 1 (zone edge), Option C assumes no correction (k = 1), and Option D uses an incorrect k.