CELE Surveying (Geomatics) — Route, Topographic and Modern SurveyingCheat Sheet
Cheat sheet for CELE Surveying (Geomatics) — Route, Topographic and Modern Surveying. Compact, printable, and organised around the concepts Professional Regulation Commission (PRC) — Board of Civil Engineering tests most frequently in the CELE 2026. Perfect for the week before exam day.
Exam context
On the CELE 2026, the Surveying (Geomatics) subtest carries a "Core" weight in Professional Regulation Commission (PRC) — Board of Civil Engineering's pattern. Route, Topographic and Modern Surveying lands at position 9th out of 9 in the standard review order. Target score is 70% weighted average, no sub-test below 50%, and roughly a meaningful share of items come from Surveying (Geomatics) on a typical CELE paper.
Route, Topographic and Modern Surveying - Cheat Sheet
Your last-minute revision companion for topographic mapping, contour interpretation, photogrammetry, and modern positioning systems. Master formulas, definitions, and common pitfalls in 30 minutes before the PRC Civil Engineer Licensure Exam.
Sections
Section Title
Topographic Surveying & Contour Lines
Important Facts
- Closely spaced contours = steep terrain; widely spaced = gentle slope.
- Contour lines never cross (except in overhangs/cliffs, rare on standard maps).
- Contours always close on themselves (form closed loops around hills or depressions).
- V-point direction in valleys = upstream (uphill); in ridges = downhill.
- Hachure marks (short lines) perpendicular to contours point toward depression (downslope).
- Elevation increases from one contour to the next in the direction perpendicular to lines.
- Slope calculation counts INTERVALS between contours, not the number of lines.
- Depression contours are marked with hachures; normal contours are not.
Key Definitions
Term
Contour Line
Example
The 100 m contour connects all points 100 m above datum.
Definition
An imaginary line joining all points of equal elevation on the ground surface.
Term
Contour Interval (CI)
Example
A 5 m contour interval means each contour line is 5 m higher than the next.
Definition
The vertical distance between successive contour lines; constant across a map.
Term
Slope (from contours)
Example
5 intervals × 5 m CI over 100 m horizontal = 25 m / 100 m = 25% slope.
Definition
Rise over run, calculated as (number of intervals × CI) / horizontal distance.
Term
Ridge
Example
Hilltops have contours that point downslope.
Definition
A line of high points where contours V downhill (away from the ridge).
Term
Valley
Example
Stream channels have contours pointing upstream (uphill).
Definition
A line of low points where contours V uphill (upstream direction).
Diagrams To Know
- Contour pattern on a hilltop (concentric circles, closest at peak).
- Valley V pattern (contours V upstream).
- Ridge pattern (contours V downslope).
- Saddle point (two peaks connected by lower ground; contours saddle-shaped).
Formulas
Formula
Scale = f / H
Meaning
f = focal length of camera (mm, convert to same units as H); H = flying height above ground (m). Scale is dimensionless ratio.
Watch Out
H MUST be flying height ABOVE GROUND (terrain), NOT above sea level. A 1000 m MSL flight over terrain at 500 m elevation = H = 500 m, not 1000 m. Also: convert focal length to same units before division (e.g., 150 mm = 0.150 m).
When To Use
Always used to find photo scale from vertical aerial photos; basis for all distance measurements on photos.
Formula
Ground distance = Photo distance × (Scale denominator)
Meaning
Scale denominator = denominator of the photo scale (e.g., if scale = 1:10,000, denominator = 10,000). Photo distance in same units as used in photo (typically mm).
Watch Out
Ensure photo distance is in SAME UNITS throughout. If scale = 1:5,000 and photo distance = 40 mm, ground distance = 40 × 5,000 = 200,000 mm = 200 m. Do NOT mix mm and m without converting.
When To Use
To find real-world ground distance from a measurement on a photo.
Formula
Photo distance = Ground distance / (Scale denominator)
Meaning
Reverse calculation: finding photo measurement given ground distance and scale.
Watch Out
Same unit consistency issue as above. Answer will be very small (typically mm for ground features measured in tens/hundreds of m).
When To Use
Planning photo interpretation or checking if a known ground feature fits on a photo.
Common Values
Value
150 mm to 300 mm
Symbol
f
Quantity
Typical aerial camera focal length
Value
2 m (mountainous), 5 m (rolling), 10 m (flat)
Symbol
CI
Quantity
Standard contour interval (topographic photos)
Value
1500 m above ground
Symbol
H
Quantity
Typical flying height (1:10,000 scale, f = 150 mm)
Section Title
Photogrammetry
Important Facts
- Scale is UNIFORM on vertical photos; varies on oblique or tilted photos.
- Larger flying height H → smaller scale (1:20,000); smaller flying height → larger scale (1:5,000).
- Focal length f is a camera property, fixed for a given sensor.
- Photo scale must account for terrain relief; working scale is f/H above GROUND, not sea level.
- Stereoscopic pair of overlapping photos allow 3D measurement and height determination.
- Overlap between successive photos typically 50–60% along flight line; 30% between adjacent flight lines.
- Ground coordinates from photo measurements require control points (known lat/lon/elev on ground).
- Orthophoto = photo geometrically corrected to map projection; no scale variation due to relief or tilt.
Key Definitions
Term
Photogrammetry
Example
Using aerial photos from a drone at 500 m altitude to create a contour map of a road corridor.
Definition
Science and technology of obtaining measurements, maps, and spatial data from photographs (aerial or terrestrial).
Term
Vertical Aerial Photo
Example
Standard topographic mapping method; assumes flat ground for uniform scale.
Definition
A photograph taken with the camera pointed straight down (nadir) from an aircraft; scale is uniform across the photo.
Term
Focal Length (f)
Example
Typical aerial cameras: 150 mm, 210 mm, 300 mm focal lengths.
Definition
Distance from camera lens to the image plane (film or sensor); measured in mm.
Term
Flying Height (H)
Example
Flight at 2400 m MSL over terrain at 600 m elevation = H = 1800 m.
Definition
Height of aircraft above the ground surface being photographed.
Term
Ground Sampling Distance (GSD)
Example
A 1:10,000 scale photo with 0.1 mm pixel size = GSD ≈ 1 m on ground.
Definition
Linear size of ground area represented by one pixel (for digital photos); related to photo scale.
Diagrams To Know
- Vertical aerial photo geometry (camera, focal length, flying height, ground footprint).
- Stereomodel geometry (two overlapping photos, base/parallax, height calculation).
- Effect of terrain relief on photo scale (higher ground = larger scale locally).
Common Values
Value
1450 m/s (varies 1400–1540 m/s)
Symbol
c
Quantity
Speed of sound in seawater (typical)
Value
50 m to 200 m (depends on purpose: navigation, dredging, etc.)
Symbol
—
Quantity
Typical sounding line spacing
Section Title
Hydrographic Surveying
Important Facts
- Positions (latitude, longitude) of sounding points fixed by GNSS/RTK for accuracy.
- Water level must be recorded continuously (tide gauge); soundings are reduced to chart datum.
- Echo sounder velocity in water typically 1450 m/s (varies with salinity, temperature).
- Systematic grid of sounding lines (e.g., 100 m spacing) ensures complete depth coverage.
- Shoreline feature (jetties, rocks, wreckage) plotted separately from sounding grid.
- Isobaths (depth contours) drawn from interpolated soundings; spacing depends on seafloor slope.
- Hazards (shallow rocks, wrecks, cables) marked and noted separately on hydrographic chart.
- Philippine waters: Standard hydrographic datum is MLLW (low water ordinary spring tides).
Key Definitions
Term
Hydrographic Survey
Example
Surveys for port approaches, river dredging, bridge foundations in tidal areas.
Definition
Survey of water bodies: depth (soundings), shoreline, bathymetry, flow direction, hazards for navigation/dredging.
Term
Sounding
Example
A sounding of 12.5 m means water depth is 12.5 m below the chart datum.
Definition
Depth measurement of water body, referenced to a chart datum (e.g., Mean Lower Low Water).
Term
Echo Sounder / Fathometer
Example
Doppler sounder in a hydrographic launch; outputs soundings automatically.
Definition
Electronic instrument that transmits a sound pulse and measures the time to echo return; calculates depth = (velocity × time) / 2.
Term
Chart Datum
Example
Philippine hydrographic surveys use MLLW as the standard datum.
Definition
Reference water level for soundings, typically Mean Lower Low Water (MLLW) in tidal areas.
Term
Bathymetry
Example
A bathymetric map of Manila Bay showing shipping channels and depth zones.
Definition
Underwater topography shown by contours (isobaths) of equal water depth.
Diagrams To Know
- Hydrographic survey layout (sounding lines, spacing, control points).
- Echo sounder principle (pulse transmission, reflection, time-to-depth conversion).
- Tidal reference (chart datum, mean sea level, high/low water marks).
- Bathymetric contours (isobaths) around a navigation channel or port.
Formulas
Formula
Horizontal Accuracy (RTK GNSS) ≈ 1–5 cm + 1 ppm baseline
Meaning
RTK (Real-Time Kinematic) GNSS gives cm-level accuracy for control and staking; error grows with baseline distance.
Watch Out
Accuracy varies with satellite geometry, atmospheric conditions, and baseline. At long baselines (>30 km), error increases. Always verify by redundant measurements.
When To Use
When precision staking, control establishment, or high-precision contouring is required.
Formula
Total Station Position = Distance × cos(Hz) + known point E, Distance × sin(Hz) + known point N
Meaning
ΔE, ΔN are computed from measured horizontal distance and azimuth; add to known station coordinates.
Watch Out
Azimuth direction (Hz) MUST be measured from TRUE NORTH or a known bearing. Vertical angle (zenith or depression) required to reduce slope distance to horizontal. Instrument height and target height must be recorded.
When To Use
Setting out (stake-out) or calculating point coordinates from a known station.
Common Values
Value
±5–10 m (standard), ±2–5 cm (differential/RTK)
Symbol
—
Quantity
GNSS absolute accuracy (post-processed)
Value
2–5 km (typical); 10+ km with reflector
Symbol
R
Quantity
Total station EDM range
Value
±1–5 seconds of arc (surveygrade)
Symbol
—
Quantity
Total station angle accuracy
Value
10–30 km from base station
Symbol
—
Quantity
RTK GNSS baseline limit (practical)
Section Title
Modern Positioning Systems
Important Facts
- GNSS provides absolute coordinates (lat/lon/elev); no need for local control if accuracy allows.
- RTK GNSS ideal for staking: real-time feedback to cm level; no backsight required.
- Total station requires backsight to known point to establish orientation; then can radiate detail from setup.
- Vertical angle in total station must be zenith angle (0° at zenith) or vertical angle (±90° from horizontal), depending on instrument.
- Slope distance must be reduced to horizontal: Horiz. dist. = Slope dist. × cos(zenith angle).
- Data from total station or GNSS must be stored in standard format (ASCII, binary) for import to GIS.
- Control accuracy hierarchy: Primary (GNSS, ±1–5 cm) → Secondary (traverse, ±5–10 cm) → Tertiary (detail, ±10–50 cm).
- Differential GNSS (DGPS) gives ~0.5 m accuracy; RTK much better but requires base station within ~30 km.
- Base station for RTK should be on known control or operated long enough to converge.
Key Definitions
Term
GNSS (Global Navigation Satellite System)
Example
GPS differential or RTK GNSS for control point establishment with cm accuracy.
Definition
Positioning system using signals from orbiting satellites (GPS, GLONASS, Galileo, BeiDou); provides latitude, longitude, elevation.
Term
GPS (Global Positioning System)
Example
Handheld GPS unit for reconnaissance; survey-grade GPS for control establishment.
Definition
U.S. satellite positioning system (constellation of ~30 satellites); standard absolute accuracy ±5–10 m, differential/RTK ±1–5 cm.
Term
RTK (Real-Time Kinematic)
Example
Field crew with RTK rover stake out building corners to ±3 cm without classical traverse.
Definition
GNSS technique using ground-based reference station broadcasting corrections; mobile receiver achieves cm accuracy in real time.
Term
Total Station
Example
Leica Viva or Sokkia series; measures horizontal distance, horizontal angle, zenith angle; calculates ΔE, ΔN, ΔH in real time.
Definition
Electronic surveying instrument combining electronic theodolite (angle measurement), EDM (distance), onboard computer, and data logger.
Term
EDM (Electro-Optical Distance Measurement)
Example
Typical EDM accuracy: ±(5 mm + 5 ppm × distance); measures up to 2–5 km.
Definition
Method of measuring distances using modulated light (infrared or laser) and phase or pulse measurement; operates in total station.
Term
GIS (Geographic Information System)
Example
ArcGIS or QGIS; receives survey data, contours, orthophotos; produces planning maps, thematic overlays.
Definition
Software system for storing, analyzing, visualizing, and managing spatial data (vector or raster) referenced to coordinate system.
Term
Control Point
Example
Primary control from GNSS adjustment; secondary control from total station traverse; used to reference all detail survey.
Definition
Ground station with known coordinates (E, N, H in adopted datum); used as reference for survey measurements.
Diagrams To Know
- RTK GNSS configuration (satellite, base station, rover receiver, correction link).
- Total station setup (instrument station, backsight, foresight, angle/distance measurements).
- Stakeout with total station or RTK (known design point, measured point, residual, correction direction).
- Data flow in surveying workflow (GNSS/total station → GIS → design, planning documents).
Formulas
Formula
Horizontal Curve Radius: R = L / (180 × Δ / π) OR R = L × 180 / (π × Δ)
Meaning
L = arc length; Δ = central angle (degrees); R = radius (m).
Watch Out
Angle Δ MUST be in degrees, not radians, for this form. If using radians, use R = L / Δ_radians. Common error: forgetting to convert degrees to radians.
When To Use
Converting arc length and angle to horizontal curve radius for highway/railway alignment.
Formula
Tangent length: T = R × tan(Δ/2)
Meaning
Distance from PC (point of curve) or PT (point of tangent) along tangent to intersection point.
Watch Out
Δ/2 MUST be in same units as tan function (degrees if calculator in DEG mode). If Δ = 60°, then Δ/2 = 30°.
When To Use
Staking tangent points of horizontal curves; finding chainage of PC and PT from PI chainage.
Formula
Chord length: C = 2R × sin(Δ/2)
Meaning
Straight-line distance from PC to PT (shorter than arc length L).
Watch Out
Δ/2 in same unit mode. Chord is always shorter than arc; if values are reversed, recalculate.
When To Use
Field measurement of curve using chord method; setting out intermediate points on curve.
Formula
Chainage at PC = Chainage at PI − T; Chainage at PT = Chainage at PC + L
Meaning
Track the along-route stationing (chainage) through horizontal curves.
Watch Out
Chainage ALWAYS increases in direction of survey. At curve: PC < PI < PT in chainage terms. Forgetting this causes major staking errors.
When To Use
Route design and staking; ensuring design points align with chainage records.
Formula
Grade (slope) = (Elevation change) / (Horizontal distance) = ΔH / Horiz. Dist.
Meaning
Expressed as decimal (0.05 = 5%), percentage (5%), or ratio (1:20).
Watch Out
Must use HORIZONTAL distance, not slope distance. A 10 m rise over 100 m horizontal ≠ 10 m rise over 100 m slope distance.
When To Use
Determining suitability of proposed grade for vehicle operation, earthwork design.
Common Values
Value
30–50 m
Symbol
R_min
Quantity
Minimum horizontal curve radius (low-speed urban road)
Value
500–1000 m
Symbol
R_min
Quantity
Minimum horizontal curve radius (high-speed highway)
Value
100–500 m (depends on grade change and sight distance)
Symbol
L_v
Quantity
Typical vertical curve length (crest)
Value
8–12%
Symbol
G
Quantity
Maximum grade (steep terrain road)
Value
8–10%
Symbol
e
Quantity
Maximum superelevation
Section Title
Route Surveying Fundamentals
Important Facts
- Horizontal curves use circular arcs; defined by radius R and central angle Δ.
- Tangent length T increases with radius and angle; longer curves need longer tangents.
- Arc length L = (π × R × Δ) / 180, where Δ in degrees.
- Vertical curves are parabolic for smooth ride and visibility; length depends on grade change and sight distance.
- Chainage increases continuously along route; curves don't reset or compress chainage.
- Cross-section perpendicular to centerline at each chainage shows earthwork profile (embankment/cut).
- Road design standards (AASHTO, local code) specify minimum radius R for design speed and superelevation.
- Superelevation (banking) on horizontal curves reduces lateral forces; maximum ~8–10% on high-speed roads.
- Sight distance (stopping, passing) determined by vertical curve length and horizontal curves; critical for safety.
Key Definitions
Term
Route Survey
Example
Surveying a new 50 km highway: horizontal alignment (curves, tangents), vertical profile (grades, sags), typical sections (pavement, shoulders, slopes).
Definition
Survey of a corridor (road, railroad, pipeline) establishing centerline alignment, profile (elevation), and cross-sections.
Term
Chainage (Stationing)
Example
Chainage 5 + 234 m means 5234 m from the start (5 km + 234 m).
Definition
Distance measured along the centerline from a reference point (usually start, = 0 + 00 m).
Term
Point of Curve (PC)
Example
Road tangent ends at PC 2 + 100; circular curve begins.
Definition
Start of a horizontal curve; transition point from straight tangent to circular arc.
Term
Point of Tangent (PT)
Example
Curve ends at PT 2 + 350; new tangent direction begins.
Definition
End of a horizontal curve; transition point from circular arc back to straight tangent.
Term
Intersection Point (PI)
Example
PI at chainage 2 + 225; curve inserted symmetrically with PC before and PT after.
Definition
Where two tangents (or extended tangents) meet; defines the curve transition geometry.
Term
Deflection Angle (Δ)
Example
A 90° curve means tangents are perpendicular; a 45° curve = gentler change.
Definition
Central angle of horizontal curve; angle change from first tangent direction to second.
Term
Vertical Curve
Example
Crest curve (summit) where upgrade meets downgrade; sag curve (valley) where downgrade meets upgrade.
Definition
Parabolic arc connecting two grades (inclines); creates smooth elevation transition.
Term
Grade
Example
A +3% grade = 3 m rise per 100 m horizontal distance; common on highways.
Definition
Slope of the centerline in the vertical plane, expressed as percentage, ratio, or decimal.
Diagrams To Know
- Horizontal curve geometry (tangents, PC, PI, PT, radius, deflection angle).
- Vertical curve profile (crest and sag curves, grades, minimum length for sight distance).
- Chainage progression through route (tangent sections, curve sections, chainage increases).
- Route cross-section (centerline, pavement, shoulders, slopes, typical ditch/embankment).
Section Title
GIS and Data Management
Important Facts
- GIS is the final destination for survey data; all coordinates, elevations, and descriptions must be loaded accurately.
- Coordinate reference system (projection, datum) MUST be consistent across all layers; mismatches cause spatial errors.
- Vector data (survey points, roads) suitable for precise feature location; raster (photos, DEM) for continuous surfaces.
- Topological relationships enforced in GIS: nodes (intersections), edges (line segments), polygons (areas bounded by edges).
- Contours created in GIS from point data (TIN or grid interpolation); contour interval and appearance set in display properties.
- Spatial analysis in GIS includes buffer, overlay, proximity, network analysis; used for design, planning, environmental assessment.
- Data quality critical: field survey accuracy directly affects GIS outputs; errors in position or attributes propagate through analysis.
- Philippine national surveys use PCS (Philippine Coordinate System) Zones; local projects may use projected UTM or local grid.
- GIS exports for design (CAD), analysis (statistics), visualization (maps, 3D models) to stakeholders and contractors.
Key Definitions
Term
Geographic Information System (GIS)
Example
ArcGIS Desktop, QGIS used to manage survey data, create contours, overlay thematic maps, generate design outputs.
Definition
Integrated software suite for collecting, storing, manipulating, analyzing, and visualizing spatially referenced data (vector or raster).
Term
Vector Data
Example
Survey points (points), road centerlines (lines), building footprints (polygons).
Definition
Geographic data represented as points, lines (polylines), or polygons with associated attributes.
Term
Raster Data
Example
Orthophoto (image), Digital Elevation Model (DEM), land-cover classification map.
Definition
Geographic data represented as grid of cells (pixels), each with a value; used for continuous phenomena.
Term
Coordinate Reference System (CRS)
Example
Philippine Coordinate System Zone 3 (PCS Zone 3), UTM Zone 51N, WGS 84.
Definition
Framework defining how geographic locations are represented (projection, datum, units).
Term
Datum
Example
Philippine Datum 1992 (PD 1992), based on WGS 84 ellipsoid, for national surveys.
Definition
Reference surface (ellipsoid or geoid) and reference point for coordinate measurements.
Term
Map Projection
Example
Universal Transverse Mercator (UTM), Philippines uses transverse Mercator projection.
Definition
Mathematical transformation from curved 3D Earth surface to flat 2D map; introduces controlled distortion.
Term
Layer (GIS)
Example
Survey points layer, contours layer, design layer stacked for analysis and visualization.
Definition
Thematic collection of geographic data; each layer represents a feature class (e.g., roads, utilities, topography).
Term
Attribute
Example
A survey point may have attributes: Point ID, Easting, Northing, Elevation, Description.
Definition
Non-spatial characteristic of a feature stored in a database table.
Diagrams To Know
- GIS data flow (survey input → GIS processing → map output).
- Vector vs raster representation (points/lines/polygons vs grid cells).
- Map projection concept (spherical Earth → flat map, North arrow, scale bar).
- GIS layer structure (stacking thematic layers, attribute tables).
Must Remember
- CONTOUR V DIRECTION: In valleys, contours V UPHILL (upstream). In ridges, contours V DOWNHILL. This is tested constantly on route reconnaissance.
- PHOTO SCALE FORMULA: Scale = f / H, where H is flying height ABOVE GROUND (not above sea level). A 1000 m MSL flight over 600 m elevation terrain = H = 400 m, not 1000 m. Unit conversion (mm to m) is critical.
- GROUND DISTANCE = PHOTO DISTANCE × SCALE DENOMINATOR: If scale is 1:5,000 and photo distance is 40 mm, ground distance = 40 × 5,000 = 200,000 mm = 200 m. Do NOT mix units; convert consistently.
- HORIZONTAL CURVE CHAINAGE: PC (Point of Curve) chainage = PI chainage − T; PT chainage = PC chainage + L (arc length). Chainage ALWAYS increases; curves don't compress or reset the stationing.
- SLOPE CALCULATION FROM CONTOURS: Count INTERVALS between contours, not lines. If 6 contour lines span 100 m horizontal distance, that's 5 intervals. If each interval = 5 m (contour interval), slope = (5 × 5) / 100 = 25%.
- VERTICAL ANGLE IN TOTAL STATION: Zenith angle measured from straight up (0° = zenith, 90° = horizon). To get horizontal distance: Horizontal = Slope distance × cos(zenith angle). Not using cos incorrectly loses points on stakeout calculations.
- RTK GNSS BASELINE: RTK accuracy is typically ±(1–5 cm); baseline limit ~30 km from base station. Beyond 30 km, error increases. Base station must be on known control or converged long enough (30+ minutes).
- HACHURE MARKS: Short lines perpendicular to contours pointing DOWNSLOPE indicate a depression (closed low area). Normal contours have no hachures. Hachures are easily overlooked but critical for terrain interpretation.
- SUPERELEVATION & GRADE: Superelevation (banking) typically max 8–10%; grade (longitudinal slope) max 8–12% depending on terrain. They are different entities: superelevation is perpendicular tilt on a curve; grade is along-centerline slope.
- GIS COORDINATE REFERENCE SYSTEM: All survey data must be in the SAME projection (e.g., PCS Zone 3, UTM Zone 51N) and datum (e.g., PD 1992). Mixing projections causes invisible spatial errors. Always verify CRS before importing survey data.
Last Minute Tips
- EXAM TIP #1 — Contour Reading: Always check if contours increase or decrease with elevation direction. Mark the elevation of one line, count intervals, multiply by contour interval (CI), and add/subtract to find any line's elevation. This is a quick confidence check.
- EXAM TIP #2 — Photo Scale Calculation: Before doing the division, convert focal length (mm) to the same units as flying height (m). Write 150 mm = 0.150 m explicitly. This one-second unit check saves 90% of photo scale errors.
- EXAM TIP #3 — Total Station Stakeout: Always record BOTH slope distance and vertical angle (zenith or depression). Many students forget the vertical angle and cannot reduce to horizontal. Horizontal distance = Slope × cos(zenith); this is non-negotiable.
- EXAM TIP #4 — Route Chainage: When a curve question appears, immediately sketch PC → PI → PT and mark their chainage relationships: PC = PI − T, PT = PC + L. Visual layout prevents chainage mixups.
- EXAM TIP #5 — GNSS Baseline: If a problem says RTK GNSS is used, check if the baseline is realistic (<30 km typical). If >50 km is implied, flag it as a red flag—accuracy claims would be questionable. This shows you understand system limitations.
Comparison Tables
Rows
Values
- ±1–5 cm (RTK); ±5–10 m (standard GPS)
- ±5 mm + 5 ppm × distance
Property
Accuracy
Values
- Global; 10–30 km from base (RTK)
- 2–5 km typical; line-of-sight
Property
Range
Values
- No backsight; real-time solution
- Requires backsight to known point
Property
Setup
Values
- Requires clear sky; poor under dense vegetation
- Works in heavy forest; no sky needed
Property
Cloud/obstruction
Values
- Base + rover: ₱500k–2M (RTK)
- Total station: ₱300k–800k
Property
Equipment cost
Values
- Very fast; visual feedback on rover screen
- Slower; requires angle/distance to compute position
Property
Staking convenience
Values
- E, N, H (absolute coordinates)
- Relative positions; requires known station reference
Property
Data output
Columns
- Aspect
- GNSS (RTK)
- Total Station
Table Title
GNSS vs. Total Station for Survey Control
Rows
Values
- >20 mm on map (at 1:5000)
- <2%
Property
Flat / Very gentle
Values
- 10–20 mm on map
- 2–5%
Property
Gently rolling
Values
- 5–10 mm on map
- 5–15%
Property
Rolling hills
Values
- 1–5 mm on map
- 15–50%
Property
Steep / mountainous
Values
- <1 mm on map; hachures used
- >50% (near vertical)
Property
Cliffs / very steep
Columns
- Terrain Type
- Contour Spacing (typical)
- Slope (approx.)
Table Title
Contour Spacing vs. Slope Steepness
Rows
Values
- 1:4,000
- 20 km × 20 km
Property
H = 600 m
Values
- 1:10,000
- 50 km × 50 km
Property
H = 1,500 m
Values
- 1:16,000
- 80 km × 80 km
Property
H = 2,400 m
Values
- 1:20,000
- 100 km × 100 km
Property
H = 3,000 m
Columns
- Flying Height (m)
- Photo Scale
- Ground footprint (5 km × 5 km photo)
Table Title
Photo Scale vs. Flying Height (f = 150 mm camera)
Rows
Values
- 25–40 m
- 3–4%
- 4–6%
Property
Urban residential (30)
Values
- 80–150 m
- 5–6%
- 6–8%
Property
Urban arterial (50)
Values
- 400–600 m
- 6–8%
- 5–8%
Property
Rural (80)
Values
- 800–1,200 m
- 8–10%
- 3–5%
Property
Expressway (100)
Columns
- Design Speed (km/h)
- Min Radius (m)
- Typical Superelevation (e)
- Max Grade (%)
Table Title
Horizontal Curve Parameters (Common Road Designs)
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