Part XII — Advanced Surveying and Remote Sensing
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Chapter 12: Photogrammetry, Total Stations, GPS/GNSS, and GIS
12.1 Photogrammetry
Photogrammetry derives measurements and maps from photographs, typically aerial photographs, using principles of overlap between successive photographs (typically 60% forward overlap and 20-30% side overlap) to enable stereoscopic (3D) viewing and measurement. It is widely used for topographic mapping over large areas more efficiently than ground-based methods.
12.2 Total Station
A total station combines an electronic theodolite (for angle measurement) with an Electronic Distance Measurement (EDM) instrument (for distance measurement) in a single unit, along with onboard data storage/processing. It allows rapid, accurate measurement of horizontal and vertical angles plus slope distance, from which horizontal distance and elevation differences are computed automatically.
12.3 GPS/GNSS
The Global Positioning System (GPS), part of the broader category of Global Navigation Satellite Systems (GNSS), determines position using signals from a constellation of satellites, requiring signals from at least four satellites for a three-dimensional position fix (three for position, one to resolve receiver clock error). Differential GPS (DGPS) improves accuracy by using a fixed reference station to correct for common errors.
12.4 GIS (Geographic Information System)
A GIS is a system for capturing, storing, analysing, and presenting spatial/geographic data, organising information into thematic layers (e.g., roads, land use, drainage) that can be overlaid and analysed together. GIS is widely used in urban planning, infrastructure management, and disaster management applications.
12.5 Remote Sensing
Remote sensing involves acquiring information about the Earth's surface from a distance, typically via satellite or aerial sensors, using reflected/emitted electromagnetic radiation. It supports applications including land-use mapping, crop monitoring, and disaster assessment, complementing conventional ground surveys.
12.6 Modern Levelling and Digital Instruments
Digital/electronic levels use electronic image processing of a bar-coded staff to automatically determine and record readings, reducing reading errors compared to conventional levels. Auto levels (automatic levels) use a compensator to automatically maintain a horizontal line of sight once roughly levelled, speeding up levelling work compared to dumpy levels requiring manual bubble centring for each reading.
Practice Set — Advanced Surveying and Remote Sensing (25 MCQs)
- Photogrammetry derives measurements primarily from:
(a) Photographs, typically aerial photographs (b) Only ground-based tape measurements (c) Only satellite radio signals with no photographs (d) Only historical maps with no photographic input - The typical forward overlap between successive aerial photographs for stereoscopic viewing is approximately:
(a) 60 percent (b) 5 percent (c) 95 percent (d) 0 percent - The typical side overlap between adjacent flight-line photographs is approximately:
(a) 20-30 percent (b) 90-100 percent (c) 0 percent (d) 60 percent, identical to forward overlap always - A total station combines an electronic theodolite with:
(a) An Electronic Distance Measurement (EDM) instrument (b) Only a barometer (c) Only a compass with no distance measurement (d) Only a magnetic sensor - A total station can directly measure:
(a) Horizontal/vertical angles and slope distance (b) Only magnetic bearing with no angle measurement (c) Only temperature (d) Only soil moisture - GPS position fixing in three dimensions requires signals from at least:
(a) Four satellites (b) One satellite (c) Two satellites (d) Twenty satellites - Of the four satellite signals needed for a 3D GPS fix, one is primarily used to resolve:
(a) Receiver clock error (b) Atmospheric pressure (c) Soil type (d) Magnetic declination - Differential GPS (DGPS) improves accuracy by using:
(a) A fixed reference station to correct common errors (b) No reference station at all (c) Only a single uncorrected satellite signal (d) A purely mechanical correction with no electronic component - GNSS is best described as:
(a) A broader category including GPS and other satellite navigation systems (b) A synonym exclusively for the US GPS system with no other system included (c) A ground-based system with no satellites (d) A purely historical, now-discontinued system - A Geographic Information System (GIS) primarily organises spatial data into:
(a) Thematic layers that can be overlaid and analysed (b) A single undifferentiated dataset with no layering (c) Only textual reports with no spatial component (d) Only historical archives with no analytical function - GIS applications commonly include:
(a) Urban planning and disaster management (b) Only recreational mapping with no practical application (c) Only historical research with no modern use (d) Only military applications exclusively - Remote sensing acquires information about the Earth's surface using:
(a) Reflected/emitted electromagnetic radiation, typically via satellite or aerial sensors (b) Only ground-based physical contact measurement (c) Only historical written records (d) Only underground seismic sensors exclusively - Remote sensing supports applications including land-use mapping and:
(a) Crop monitoring and disaster assessment (b) Only entertainment media production (c) Only currency printing (d) Only judicial recordkeeping - Digital/electronic levels determine readings using:
(a) Electronic image processing of a bar-coded staff (b) Manual estimation with no electronic component (c) Only magnetic compass readings (d) Only satellite signals with no staff reading - Auto (automatic) levels maintain a horizontal line of sight using a:
(a) Compensator (b) Manual bubble adjustment for every single reading with no automation (c) Magnetic needle (d) Barometric sensor - Compared to a dumpy level, an auto level's main practical advantage is:
(a) Faster levelling work due to automatic horizontal-line maintenance (b) Higher cost with no speed benefit (c) Complete elimination of any need for a levelling staff (d) No practical difference at all - Total stations, compared to older theodolite-plus-chain surveys, offer the advantage of:
(a) Faster, more accurate, integrated angle and distance measurement (b) No measurement capability at all (c) Only angle measurement with no distance capability (d) Only distance measurement with no angle capability - GIS overlay analysis allows engineers/planners to:
(a) Combine multiple spatial data layers for integrated analysis (b) Analyse only a single, non-combinable dataset (c) Perform no spatial analysis at all (d) Replace the need for any field survey entirely and permanently - Photogrammetry is particularly efficient, compared to ground surveys, for:
(a) Topographic mapping over large areas (b) Measuring a single small room's dimensions (c) Testing concrete strength (d) Measuring soil permeability - EDM (Electronic Distance Measurement) instruments determine distance by measuring:
(a) The travel time/phase shift of a transmitted electromagnetic signal (b) Only manual tape readings (c) Only barometric pressure differences (d) Only magnetic field strength - A key advantage of GNSS-based surveying over conventional traversing is:
(a) The ability to determine position without requiring intervisibility between all points (b) A complete elimination of any need for satellites (c) Reliance solely on magnetic compass bearings (d) No advantage at all over conventional methods - Remote sensing data is commonly captured by sensors mounted on:
(a) Satellites or aircraft (b) Only handheld ground instruments (c) Only underwater submarines exclusively (d) Only stationary ground-based towers with no aerial or satellite platform - GIS thematic layers might commonly include roads, land use, and:
(a) Drainage (b) Only unrelated financial data (c) Only sports statistics (d) Only literary records - The combination of a total station's angle and distance data allows automatic computation of:
(a) Horizontal distance and elevation difference (b) Only soil bearing capacity (c) Only concrete slump value (d) Only cement grade - Modern surveying technologies (total stations, GPS/GNSS, GIS, remote sensing) collectively have made surveying work:
(a) Faster and more accurate compared to traditional manual methods (b) Entirely obsolete with no ongoing engineering relevance (c) Impossible without ground-based chains (d) Irrelevant to civil engineering practice
Answer Key with Explanations
1.(a) Photogrammetry uses photographs, typically aerial.
2.(a) Forward overlap is typically about 60 percent.
3.(a) Side overlap is typically about 20-30 percent.
4.(a) A total station combines a theodolite with an EDM instrument.
5.(a) Total stations measure horizontal/vertical angles and slope distance.
6.(a) 3D GPS fixing needs at least four satellites.
7.(a) The fourth satellite signal resolves receiver clock error.
8.(a) DGPS uses a fixed reference station for error correction.
9.(a) GNSS is the broader category including GPS and other systems.
10.(a) GIS organises data into overlay-able thematic layers.
11.(a) GIS supports urban planning and disaster management, among other uses.
12.(a) Remote sensing uses reflected/emitted electromagnetic radiation via satellite/aerial sensors.
13.(a) Remote sensing supports crop monitoring and disaster assessment.
14.(a) Digital levels use electronic image processing of a bar-coded staff.
15.(a) Auto levels use a compensator for automatic horizontal line maintenance.
16.(a) Auto levels speed up levelling versus manual dumpy-level bubble centring.
17.(a) Total stations offer faster, integrated, accurate angle/distance measurement.
18.(a) GIS overlay analysis combines multiple layers for integrated analysis.
19.(a) Photogrammetry is efficient for large-area topographic mapping.
20.(a) EDM measures distance via signal travel time/phase shift.
21.(a) GNSS surveying doesn't require intervisibility between all points, unlike traversing.
22.(a) Remote sensing sensors are mounted on satellites or aircraft.
23.(a) GIS layers commonly include drainage alongside roads and land use.
24.(a) Total station data yields horizontal distance and elevation difference.
25.(a) Modern surveying technologies have made surveying faster and more accurate.