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.
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
Contour Line
Example
The 100 m contour connects all points 100 m above datum.
An imaginary line joining all points of equal elevation on the ground surface.
Contour Interval (CI)
Example
A 5 m contour interval means each contour line is 5 m higher than the next.
The vertical distance between successive contour lines; constant across a map.
Slope (from contours)
Example
5 intervals × 5 m CI over 100 m horizontal = 25 m / 100 m = 25% slope.
Rise over run, calculated as (number of intervals × CI) / horizontal distance.
Ridge
Example
Hilltops have contours that point downslope.
A line of high points where contours V downhill (away from the ridge).
Valley
Example
Stream channels have contours pointing upstream (uphill).
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).
Photogrammetry
Formulas
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.
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.
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)
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
Photogrammetry
Example
Using aerial photos from a drone at 500 m altitude to create a contour map of a road corridor.
Science and technology of obtaining measurements, maps, and spatial data from photographs (aerial or terrestrial).
Vertical Aerial Photo
Example
Standard topographic mapping method; assumes flat ground for uniform scale.
A photograph taken with the camera pointed straight down (nadir) from an aircraft; scale is uniform across the photo.
Focal Length (f)
Example
Typical aerial cameras: 150 mm, 210 mm, 300 mm focal lengths.
Distance from camera lens to the image plane (film or sensor); measured in mm.
Flying Height (H)
Example
Flight at 2400 m MSL over terrain at 600 m elevation = H = 1800 m.
Height of aircraft above the ground surface being photographed.
Ground Sampling Distance (GSD)
Example
A 1:10,000 scale photo with 0.1 mm pixel size = GSD ≈ 1 m on ground.
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).
Hydrographic Surveying
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
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
Hydrographic Survey
Example
Surveys for port approaches, river dredging, bridge foundations in tidal areas.
Survey of water bodies: depth (soundings), shoreline, bathymetry, flow direction, hazards for navigation/dredging.
Sounding
Example
A sounding of 12.5 m means water depth is 12.5 m below the chart datum.
Depth measurement of water body, referenced to a chart datum (e.g., Mean Lower Low Water).
Echo Sounder / Fathometer
Example
Doppler sounder in a hydrographic launch; outputs soundings automatically.
Electronic instrument that transmits a sound pulse and measures the time to echo return; calculates depth = (velocity × time) / 2.
Chart Datum
Example
Philippine hydrographic surveys use MLLW as the standard datum.
Reference water level for soundings, typically Mean Lower Low Water (MLLW) in tidal areas.
Bathymetry
Example
A bathymetric map of Manila Bay showing shipping channels and depth zones.
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.
Modern Positioning Systems
Formulas
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.
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)
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
GNSS (Global Navigation Satellite System)
Example
GPS differential or RTK GNSS for control point establishment with cm accuracy.
Positioning system using signals from orbiting satellites (GPS, GLONASS, Galileo, BeiDou); provides latitude, longitude, elevation.
GPS (Global Positioning System)
Example
Handheld GPS unit for reconnaissance; survey-grade GPS for control establishment.
U.S. satellite positioning system (constellation of ~30 satellites); standard absolute accuracy ±5–10 m, differential/RTK ±1–5 cm.
RTK (Real-Time Kinematic)
Example
Field crew with RTK rover stake out building corners to ±3 cm without classical traverse.
GNSS technique using ground-based reference station broadcasting corrections; mobile receiver achieves cm accuracy in real time.
Total Station
Example
Leica Viva or Sokkia series; measures horizontal distance, horizontal angle, zenith angle; calculates ΔE, ΔN, ΔH in real time.
Electronic surveying instrument combining electronic theodolite (angle measurement), EDM (distance), onboard computer, and data logger.
EDM (Electro-Optical Distance Measurement)
Example
Typical EDM accuracy: ±(5 mm + 5 ppm × distance); measures up to 2–5 km.
Method of measuring distances using modulated light (infrared or laser) and phase or pulse measurement; operates in total station.
GIS (Geographic Information System)
Example
ArcGIS or QGIS; receives survey data, contours, orthophotos; produces planning maps, thematic overlays.
Software system for storing, analyzing, visualizing, and managing spatial data (vector or raster) referenced to coordinate system.
Control Point
Example
Primary control from GNSS adjustment; secondary control from total station traverse; used to reference all detail survey.
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).
Route Surveying Fundamentals
Formulas
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.
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.
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.
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.
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
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
Route Survey
Example
Surveying a new 50 km highway: horizontal alignment (curves, tangents), vertical profile (grades, sags), typical sections (pavement, shoulders, slopes).
Survey of a corridor (road, railroad, pipeline) establishing centerline alignment, profile (elevation), and cross-sections.
Chainage (Stationing)
Example
Chainage 5 + 234 m means 5234 m from the start (5 km + 234 m).
Distance measured along the centerline from a reference point (usually start, = 0 + 00 m).
Point of Curve (PC)
Example
Road tangent ends at PC 2 + 100; circular curve begins.
Start of a horizontal curve; transition point from straight tangent to circular arc.
Point of Tangent (PT)
Example
Curve ends at PT 2 + 350; new tangent direction begins.
End of a horizontal curve; transition point from circular arc back to straight tangent.
Intersection Point (PI)
Example
PI at chainage 2 + 225; curve inserted symmetrically with PC before and PT after.
Where two tangents (or extended tangents) meet; defines the curve transition geometry.
Deflection Angle (Δ)
Example
A 90° curve means tangents are perpendicular; a 45° curve = gentler change.
Central angle of horizontal curve; angle change from first tangent direction to second.
Vertical Curve
Example
Crest curve (summit) where upgrade meets downgrade; sag curve (valley) where downgrade meets upgrade.
Parabolic arc connecting two grades (inclines); creates smooth elevation transition.
Grade
Example
A +3% grade = 3 m rise per 100 m horizontal distance; common on highways.
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).
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
Geographic Information System (GIS)
Example
ArcGIS Desktop, QGIS used to manage survey data, create contours, overlay thematic maps, generate design outputs.
Integrated software suite for collecting, storing, manipulating, analyzing, and visualizing spatially referenced data (vector or raster).
Vector Data
Example
Survey points (points), road centerlines (lines), building footprints (polygons).
Geographic data represented as points, lines (polylines), or polygons with associated attributes.
Raster Data
Example
Orthophoto (image), Digital Elevation Model (DEM), land-cover classification map.
Geographic data represented as grid of cells (pixels), each with a value; used for continuous phenomena.
Coordinate Reference System (CRS)
Example
Philippine Coordinate System Zone 3 (PCS Zone 3), UTM Zone 51N, WGS 84.
Framework defining how geographic locations are represented (projection, datum, units).
Datum
Example
Philippine Datum 1992 (PD 1992), based on WGS 84 ellipsoid, for national surveys.
Reference surface (ellipsoid or geoid) and reference point for coordinate measurements.
Map Projection
Example
Universal Transverse Mercator (UTM), Philippines uses transverse Mercator projection.
Mathematical transformation from curved 3D Earth surface to flat 2D map; introduces controlled distortion.
Layer (GIS)
Example
Survey points layer, contours layer, design layer stacked for analysis and visualization.
Thematic collection of geographic data; each layer represents a feature class (e.g., roads, utilities, topography).
Attribute
Example
A survey point may have attributes: Point ID, Easting, Northing, Elevation, Description.
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
GNSS vs. Total Station for Survey Control
| Aspect | GNSS (RTK) | Total Station |
|---|---|---|
| Accuracy | ±1–5 cm (RTK); ±5–10 m (standard GPS) | ±5 mm + 5 ppm × distance |
| Range | Global; 10–30 km from base (RTK) | 2–5 km typical; line-of-sight |
| Setup | No backsight; real-time solution | Requires backsight to known point |
| Cloud/obstruction | Requires clear sky; poor under dense vegetation | Works in heavy forest; no sky needed |
| Equipment cost | Base + rover: ₱500k–2M (RTK) | Total station: ₱300k–800k |
| Staking convenience | Very fast; visual feedback on rover screen | Slower; requires angle/distance to compute position |
| Data output | E, N, H (absolute coordinates) | Relative positions; requires known station reference |
Contour Spacing vs. Slope Steepness
| Terrain Type | Contour Spacing (typical) | Slope (approx.) |
|---|---|---|
| Flat / Very gentle | >20 mm on map (at 1:5000) | <2% |
| Gently rolling | 10–20 mm on map | 2–5% |
| Rolling hills | 5–10 mm on map | 5–15% |
| Steep / mountainous | 1–5 mm on map | 15–50% |
| Cliffs / very steep | <1 mm on map; hachures used | >50% (near vertical) |
Photo Scale vs. Flying Height (f = 150 mm camera)
| Flying Height (m) | Photo Scale | Ground footprint (5 km × 5 km photo) |
|---|---|---|
| H = 600 m | 1:4,000 | 20 km × 20 km |
| H = 1,500 m | 1:10,000 | 50 km × 50 km |
| H = 2,400 m | 1:16,000 | 80 km × 80 km |
| H = 3,000 m | 1:20,000 | 100 km × 100 km |
Horizontal Curve Parameters (Common Road Designs)
| Design Speed (km/h) | Min Radius (m) | Typical Superelevation (e) | Max Grade (%) |
|---|---|---|---|
| Urban residential (30) | 25–40 m | 3–4% | 4–6% |
| Urban arterial (50) | 80–150 m | 5–6% | 6–8% |
| Rural (80) | 400–600 m | 6–8% | 5–8% |
| Expressway (100) | 800–1,200 m | 8–10% | 3–5% |
Diagrams
Photo Scale & Ground Distance Problem-Solving
Step-by-step decision tree for solving photo scale and ground distance problems. Handles given data scenarios and unit conversion checkpoints.
Route Surveying Key Concepts
Mind map organizing route surveying topics into horizontal alignment, vertical profile, cross-sections, and staking methods. Shows hierarchical relationships between elements.
Contour Interpretation Decision Tree
Decision logic for interpreting contour patterns: distinguishing hills from depressions, valleys from ridges, steep from gentle terrain, and calculating slope from contour spacing.
Survey Data Flow: Field to GIS
Sequence showing the flow of survey data from field instruments through post-processing to final GIS integration and output for design and planning.
Typical Exam Question Distribution - Route & Topographic Surveying
Distribution of question types in the PRC Civil Engineer Licensure Exam for this chapter. Contour interpretation and photo problems dominate; prepare accordingly.