1
CONS 127 Final Exam Open Notes 2024|2025 with complete
solutions|University of British Columbia
Map Projections and Distortions
1. Types of Projections:
○ Conformal: Preserves shape/direction; distorts area and distance.
■ Example: Mercator projection.
○ Equivalent/Equal Area: Preserves area; distorts distance and
shape/direction.
■ Example: Mollweide projection.
○ Equidistant: Preserves distance (from a single point); distorts area and
shape/direction.
■ Example: Azimuthal equidistant projection.
○ Compromise: Distorts all (distance, area, and shape/direction) but minimizes
errors overall.
■ Example: Robinson projection.
2. Mercator vs Mollweide Projections:
○ Mercator: Distorts area near poles (e.g., Greenland appears larger than
Africa).
■ Used for navigation due to straight-line trajectories.
○ Mollweide: Better for relative area accuracy; often used in thematic maps for
global datasets.
3. Scale:
○ Large Scale Maps: Zoomed in; more detail (e.g., 1:10,000 city maps).
○ Small Scale Maps: Zoomed out; less detail (e.g., 1:1,000,000 world maps).
Practice Question Answer:
● Question: Compare the types of distortions between Mercator and Mollweide
projections. Why might one be preferred for environmental studies?
○ Answer: Mercator distorts area near the poles, making it unsuitable for
representing global area data accurately. Mollweide minimizes these
distortions, preserving relative areas, which is preferable for environmental
studies like deforestation mapping.
GNSS (Global Navigation Satellite System)
1. Steps for Finding Location:
○ Download almanac.
○ Download ephemeris and synchronize receiver clock.
, 2
○ Measure time delay from at least 4 satellites.
○ Determine range (distance to each satellite).
○ Calculate X, Y, Z coordinates using trilateration.
2. GNSS Errors:
○ Receiver Errors: Quality of the receiver affects precision.
○ Clock Errors: Timing inaccuracies between receiver and satellite clocks.
○ Ephemeris Errors: Incorrect satellite position data due to orbital drift.
○ Tropospheric/Ionospheric Delays: Atmospheric interference affecting signal
speed.
○ Multipath Error: Signal reflection from buildings or terrain causing
inaccuracies.
3. Error Reduction Strategies:
○ Before Measurement: Plan mission during optimal satellite visibility.
○ During Measurement: Avoid obstructions, take multiple readings.
○ After Measurement: Use post-processing software to correct errors.
4. GNSS Systems:
○ GPS (Global Positioning System): US-owned, globally used.
○ DGPS (Differential GPS): Uses base stations for correction.
○ RTK (Real-Time Kinematic): Provides real-time corrections for higher
accuracy.
○ A-GPS (Assisted GPS): Reduces time to first fix by using cellular networks.
Practice Question Answer:
● Question: What are the primary differences between DGPS and RTK GPS, and in
which applications would each be preferred?
○ Answer: DGPS uses base stations for post-processed corrections, ideal for
applications like general surveying. RTK GPS provides real-time corrections,
preferred for precision tasks like construction or agriculture.
Spectral Signatures
1. Definition: The unique pattern of reflected energy from a material across different
wavelengths, typically visualized as a graph.
2. Factors Controlling Leaf Reflectance:
○ Visible Spectrum: Reflectance governed by pigments (e.g., chlorophyll
absorbs blue/red, reflects green).
○ Near-Infrared (NIR): High reflectance due to spongy mesophyll structure in
healthy leaves.
○ Mid-Infrared (MIR): Reflectance inversely related to water content; low water
content = high MIR reflectance.
CONS 127 Final Exam Open Notes 2024|2025 with complete
solutions|University of British Columbia
Map Projections and Distortions
1. Types of Projections:
○ Conformal: Preserves shape/direction; distorts area and distance.
■ Example: Mercator projection.
○ Equivalent/Equal Area: Preserves area; distorts distance and
shape/direction.
■ Example: Mollweide projection.
○ Equidistant: Preserves distance (from a single point); distorts area and
shape/direction.
■ Example: Azimuthal equidistant projection.
○ Compromise: Distorts all (distance, area, and shape/direction) but minimizes
errors overall.
■ Example: Robinson projection.
2. Mercator vs Mollweide Projections:
○ Mercator: Distorts area near poles (e.g., Greenland appears larger than
Africa).
■ Used for navigation due to straight-line trajectories.
○ Mollweide: Better for relative area accuracy; often used in thematic maps for
global datasets.
3. Scale:
○ Large Scale Maps: Zoomed in; more detail (e.g., 1:10,000 city maps).
○ Small Scale Maps: Zoomed out; less detail (e.g., 1:1,000,000 world maps).
Practice Question Answer:
● Question: Compare the types of distortions between Mercator and Mollweide
projections. Why might one be preferred for environmental studies?
○ Answer: Mercator distorts area near the poles, making it unsuitable for
representing global area data accurately. Mollweide minimizes these
distortions, preserving relative areas, which is preferable for environmental
studies like deforestation mapping.
GNSS (Global Navigation Satellite System)
1. Steps for Finding Location:
○ Download almanac.
○ Download ephemeris and synchronize receiver clock.
, 2
○ Measure time delay from at least 4 satellites.
○ Determine range (distance to each satellite).
○ Calculate X, Y, Z coordinates using trilateration.
2. GNSS Errors:
○ Receiver Errors: Quality of the receiver affects precision.
○ Clock Errors: Timing inaccuracies between receiver and satellite clocks.
○ Ephemeris Errors: Incorrect satellite position data due to orbital drift.
○ Tropospheric/Ionospheric Delays: Atmospheric interference affecting signal
speed.
○ Multipath Error: Signal reflection from buildings or terrain causing
inaccuracies.
3. Error Reduction Strategies:
○ Before Measurement: Plan mission during optimal satellite visibility.
○ During Measurement: Avoid obstructions, take multiple readings.
○ After Measurement: Use post-processing software to correct errors.
4. GNSS Systems:
○ GPS (Global Positioning System): US-owned, globally used.
○ DGPS (Differential GPS): Uses base stations for correction.
○ RTK (Real-Time Kinematic): Provides real-time corrections for higher
accuracy.
○ A-GPS (Assisted GPS): Reduces time to first fix by using cellular networks.
Practice Question Answer:
● Question: What are the primary differences between DGPS and RTK GPS, and in
which applications would each be preferred?
○ Answer: DGPS uses base stations for post-processed corrections, ideal for
applications like general surveying. RTK GPS provides real-time corrections,
preferred for precision tasks like construction or agriculture.
Spectral Signatures
1. Definition: The unique pattern of reflected energy from a material across different
wavelengths, typically visualized as a graph.
2. Factors Controlling Leaf Reflectance:
○ Visible Spectrum: Reflectance governed by pigments (e.g., chlorophyll
absorbs blue/red, reflects green).
○ Near-Infrared (NIR): High reflectance due to spongy mesophyll structure in
healthy leaves.
○ Mid-Infrared (MIR): Reflectance inversely related to water content; low water
content = high MIR reflectance.
