Cons 127 Final Exam Questions PDF

Attributes of Position • • • • • • • What is latitude and longitude? Latitude is the angle that describes the north-south position. A line of latitude goes ‘horizontally’ – from east to west such as the equator. Longitude is the angle that describes the east-west position. A line of longitude...

Attributes of Position • • • • • • • What is latitude and longitude? Latitude is the angle that describes the north-south position. A line of latitude goes ‘horizontally’ – from east to west such as the equator. Longitude is the angle that describes the east-west position. A line of longitude goes ‘vertically’ from north to south forming a half-circle meridian such as the prime meridian, longitude is expressed in relation to how far a location is from the prime meridian. Where is the prime meridian? The Prime Meridian is the line of longitude at 0°, the reason why this line of longitude in particular is the starting point (0°) is largely an arbitrary decision. The Prime Meridian has been defined to be located at the Royal Observatory at Greenwich in London, England. However this definition is known to be slightly off and now a common reference meridian used is maintained by the IERS. What is a parallel? A parallel is a circle connecting all locations at a given latitude. For example, the 49th parallel lies on the circle of latitude 49° north of the equator. (This is much of the Canada-USA border) What are the three ways the earth’s shape can be mathematically defined? - The first way is by using a sphere representation, it is assuming the earth is perfectly round and the radius is constant (semi major axis = semi minor axis). - The second way is by using an ellipsoid, the earth is flattened at the poles and bulges at the equator due to its revolution, this works well for direct mathematical computations. (semi major axis ≠ semi minor axis) - The third way is by using a geoid representation, this is a physical approximation of the exact figure of the earth, making use of complex physical models and gravity readings of the earth’s surface. It can be used to measure surface elevations with a high degree of accuracy. What is the only correct representation of the Earth’s surface? A geoid representation, explained above. What is the main difference between an equivalent and conformal projection? - An equivalent/conic/equal-area projection will work to preserve area, however the shape of countries may become distorted. An example of such a projection is the gall-peters. - A conformal/cylindrical projection works to preserve angles between positions, however the size of areas will become distorted the farther from the equator they are. This is convenient for sea navigation, an example of such a projection is the Mercator. Considering the case of Africa and Greenland, describe how map projections might influence the perspective of the map viewer. On the Mercator projection, countries closer to the poles appear to have a significantly larger area than what they actually have. Greenland appears to be a similar size to the continent of Africa on the Mercator map, however it is actually 1/14th the area of Africa. Africa is huge – it has the same area as the US, China, India, Japan, much of Europe combined with room to spare, yet we would never know it based off of the Mercator map. Distance and Scale • What were some previously used measurement metrics? There are many, but they all tend to be linked to our bodies: Thumb-breadth, hand-breadth, span, fathom, furlong, cubits… • • • • • • • How was a metre first defined? The metre was first defined in 1793 as “one ten millionth of the distance from the equator to the north pole.” Then from 1889 to the 1960’s, the standard was a platinum and iridium bar stored in the International Bureau of Weights and measures in Paris. How is it defined now? The metre is now defined based of the speed of light – “the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second.” What is the name of the unit which is equal to 1000 nm? One micrometer (1 µm) = 1000 nm Example: Visible spectrum: 0.4 – 0.7 µm = 400 – 700nm Which covers more area, a small or a large scale map? Small scale maps cover a large area with coarse detail. Large scale maps cover a small area with great detail and accuracy. What are two ways scale can be indicated on a map? One way is to use a bar scale that is placed on the map. Another way is to have a fractional/ratio scale that shows how much area is represented by one inch/cm on the map. What kind of map scale would be appropriate for representing large countries and/or continents? For a city neighbourhood? Worldwide – 1:40,000,000 Continental – 1:20,000,000 National – 1:10,000,000 Provincial, regional, state – 1:1,000,000 Metropolitan Areas – 1:50,000 Cities – 1:30,000 Neighbourhood – 1:15,000 Cadastral – 1:1500 – 1:500 Name some devices which can measure distances at different scales? Electron microscope – Accelerated electrons used as a source of illumination, used to observe microorganisms, cells, molecules, metals and crystals. Optical microscope – Use visible light to magnify small samples, used for biotechnology, microbiology pharmaceutical research etc. Camera – Creates static/moving images of the observed scene. Telescope – Aids in the observation of remote objects, previously composed of lenses and mirrors but now senses EM spectrum such as radio, x-ray, gamma-ray, and high energy particles. History of Positioning • What is the difference between relative and absolute positioning? o Relative positioning – determining a location relative to other landmarks or features. One example of this is dead-reckoning where you calculate position by using a previously determined position, and advancing that position based upon estimated speed over time. Another example is pilotage where you use visual triangulation on known landmarks, this was often used with maps and nautical charts. o Absolute positioning – this is represented by coordinates of a point in space (lat/lon), also known as position fixing. • • • What is a geodetic marker? Geodetic markers are points whose relative and absolute positions are accurately established. Thus, a geodetic network is a network of points which we know the exact coordinates of. They can then be used to calculate other points through triangulation. In Ocean navigation which is easier to calculate, latitude or longitude? Latitude is easier to calculate, the height of any star in the sky will change with the observers latitude (observers will often will point to the north star in the northern hemisphere to determine latitude). Longitude is more difficult to calculate and requires a precise clock to calculate the difference in hours and minutes between the prime meridian and the current location because the earth will revolve once on its axis every 24 hours. That’s a change of 1° every four minutes, 15° every hour. What is the critical measurement to obtain an accurate longitude? Time – as mentioned above. Calculating longitude was an issue for a while that resulted in many shipwrecks as there were no precise clocks that could be placed on a ship. This clock issue was solved by John Harrison with the H4 marine chronometer design in 1761. Observations from Space, Orbits and the International Space Station • • • • • • • • What is an orbit? An orbit is a curved path around a celestial object. It is created from the gravitational attraction between two objects. Orbit is the effect of continuously falling towards the target. What are the ways that we can define space? Space is where there’s a lack of an atmosphere. There is no distinct boundary that marks the beginning of space. But at around ~400km the concentration of air molecules is very low and decreases logarithmically, so it is often said that is where space starts. What are the levels of atmosphere? Earth -> Troposphere -> Stratosphere -> Mesosphere -> Thermosphere -> Exosphere What are the 4 types of orbits, how far are they, and what are their uses? Low-Earth – 400km altitude. Not a stable orbit because it’s susceptible to atmospheric drag and orbital decay. It has the ISS, is good for microgravity experiments, human space flight, and ISS experiments on human health, plant growth, and genetic expression. Close Elliptical – 600 – 2000km altitude. This orbit is good for earth observation satellites such as, imaging, and spectral observation. Far Elliptical – ~20,000km altitude. This orbit is good for GPS/GNSS systems Geostationary – ~35,000km altitude. This orbit is interesting because it stays locked to the earths side and will orbit at the same rate as the earth’s axis. This is good for weather satellites, telecommunications, and satellite TV. Which type of orbit would be used to monitor weather? Geostationary. The good thing with geostationary is that it is locked in place so it can consistently provide weather information on the same areas. Which type of orbit is used for GPS tracking? Far elliptical Which orbit is best for getting to and returning from space easily? Low-earth orbit because gravity still has an effect at this location. The ISS has to be continuously boosted to remain in this orbit. Which orbit type are most remote sensing satellites in? Why? • • Most remote sensing satellites are in close elliptical orbit. In close elliptical orbit, the satellites are able to travel around the earth on a very predictable path, this results in satellite “trains” where multiple different satellite sensors will make measurements at a specific location at the same time every day. Name three types of satellites (i.e. performing different functions) that use geostationary orbits? Weather satellites, telecommunications, and satellite TV. What are some forms of space junk collection? Net capture, harpoon, and dragsail (inflatable boom). Also, newer satellites will have rockets in them that will launch themselves back into the earth’s atmosphere once they hit end of life. Observations from Space: Global Navigation Satellite Systems (GNSS) 1. What does GNSS stand for? How does it differ from GPS? GNSS stands for Global Navigation Satellite Systems. GPS (global positioning system / NAVSTAR) is just one system within GNSS as a whole. GNSS is comprised of GPS (USA) + GLONASS (Russia) + GALILEO (EU) + BEIDOU (China) + QZSS (Japan). Our mobile devices are able to read all of them, there will often be times where our devices are reading from multiple of these satellites at the same time. 2. What is the minimum number of satellite needed for an accurate positional location? We need a minimum cover of 4 visible satellites at any given time. 3 of these are for the trilateration computation, and the 4+ satellites are for confirmation, redundancy, and extra accuracy. 3. What two key types of information are sent by GNSS satellites to receivers that allow for the determining of position? The almanac is a data set that contains more coarse information such as the satellite constellation’s status, locations, and health. The almanac data is the same system wide and is valid for 90 days, this information is helpful for GPS receivers as it can make it faster to locate the first few satellites in the system. Almanac data is also available online, this makes it often easier and faster for internet-connected devices to find their location, while it may take a few minutes for non-internet-connected devices to retrieve the almanac from satellites. The ephemeris is a more critical piece of information as it provides accurate information on each individual GNSS satellite such as its exact location, time, clock corrections, orbit, and the age of its data. It is valid for 2 hours and is unique for each satellite. A GPS receiver must have ephemeris data to operate properly while the almanac is not critically needed, it is just helpful to get devices on the system coordinated and operating quicker. 4. Explain the causes of two different types of dilution of position error and how those errors can be minimized. DOP values are related to how close GNSS satellites are to each other – a higher DOP value means many satellites are close together and a lower DOP value means that the satellites are farther apart. Lower DOP values are better. Another factor impacting DOP is the number of satellites that are visible. DOP errors can be minimized by having the satellites follow orbits that have the least clustering and highest combined visibility at any given time. 5. How is distance from a GNSS satellite to a receiver measured? What are the steps of determining a position? The speed of light is used to calculate distances. The ranging measurements are based on the timing between the satellite transmitter and the users receiver being coordinated. The position is determined in 5 steps: download the almanac, download the ephemeris, measure ΔT to at least 4 satellites, determine range, calculate x,y,z. 6. What type of error is caused by GNSS signals bouncing off of objects near a receiver? Accuracy is influenced by: Number and position of satellites, Atmospheric effects, Obstructions (trees, buildings etc.), Receiver quality, Corrections / post-processing. Typically your GNSS receiver will be accurate ~3-15m, 95% of the time. 7. How does assisted GPS differ from differential GPS? Assisted GPS (A-GPS) is when almanac data is downloaded via data connections such as WiFi/LTE/4G/3G, this speeds up the process of locating satellites versus waiting for a satellite signal. This is why cellphones are faster at retrieving location with internet on, and it’s also why old-school car GPS systems are often so slow at getting started because it has to download all this information from a satellite vs. a data connection. Differential GPS is a method of increasing measurement accuracy, it requires having an additional receiver that is in a known position (the reference station), using a GPS receiver with this additional reference station can help increase the accuracy to just a few centimeters. 8. What spatial errors could you expect with a phone based GPS? Phone GPS receivers are not as accurate as more the expensive professional measurement devices, and you can expect an accuracy within 3-15 metres. Common forms of error could include signal bounce and distortion from buildings and mountains. 9. What are the three segments of GNSS systems? Space Segment, Control Segment, User Segment. 10. When will GPS not work? GNSS won’t work when inside tunnels, inside dense buildings, dense forests, between tall buildings, underwater, and underground. Essentially whenever the signal from a satellite cannot be received. Observing Systems in Space and Canada’s Role 1. In what decade were the first images collected from Space? From what platform? The first images from space came from unmanned rockets, the very first was an American V2 rocket in 1948. These images show a side view of New Mexico and the Gulf of California. Rockets then became a popular method of spy photography. 2. What are some disadvantages of acquiring images from rockets? It’s expensive to launch a rocket every time you want to take a photo. There is also the issue (back then) of having to retrieve the film imagery from the rocket afterwards which probably proved to be a costly and difficult procedure. There is also the issue of having to stitch together and process these images, and an issue of quality. 3. What was the first remote sensing based application? The first application of remote sensing earth observation was weather satellites. This helped greatly with monitoring weather patterns, systems, and storms. The first televised photo from space was from the TIROS weather satellite in 1960. 4. Explain some of the earth observation systems • WorldView o Owned privately by DigitalGlobe, there are currently 4 WorldView satellites o Provide high spatial resolution, as low as 30cm pixel. Primarily visible and NIR spectrum. • ICESAT o 70m ‘footprint’ o Space-borne laser ranging, monitor ice, cloud, and land elevation • Landsat o 30m pixel, 60 day return period o 8 satellites comprised of 4 sensors • MODIS (TERRA/AQUA) o 250-500m pixel for land research, 1000m pixel for ocean and atmosphere research o 1-2 day return period 5. Select a Canadian innovation relevant to observing the Earth. Why is it important? • CanadARM: A series of robotic arms for use on the ISS. It is used to deploy, maneuver and capture payloads. • RADARSAT constellation: Provides remote sensing data at 3-8m pixels, to help monitor ice, surface wind, oil pollution, ships, disasters, and ecosystems. • Urthecast: Provides the first instances of video recordings from space. 6. What are three useful characteristics of the data provided by Earth observing systems? Earth observation systems allows us to monitor resources efficiently, repeatedly, and constantly. It allows us to monitor a large amount much easier than any other method. 7. What is the name of the project on the International Space Station that provides high resolution video of the Earth? Urthecast Observing the Earth Using the Electromagnetic Spectrum 1. Define wavelength and frequency. Wavelength (λ) is the distance between peaks of a wave Frequency (f or v) is the number of wavelengths that fit within a 1 second window. 2. What is the symbol for the speed of light? c = 299 792 458 m/s 3. What is the shortest wavelength emitted by the sun? X-rays. (Gamma rays are produced in the sun but not emitted because they are converted to lower energy photons before being released, however gamma rays are released by hotter objects in our universe such as neutron starts and black hole regions.) 4. 100 nm is now many micrometers (or microns)? 1 nm = 1*10-9m 1 µm = 1*10-6m nm to µm -> divide nm by 1000 ∴ 100nm = 0.1 µm 5. What is the colour of the longest wavelength of visible light? The longest wavelength of visible light (~700nm) corresponds to the color red. The shortest wavelength of visible light (~400nm) corresponds to the color violet. 6. What happens to near infrared light when it hits water? Water in NIR has a high absorption (low reflectance), this makes bodies of water easy to detect and locate using NIR remote sensing data. 7. What are the three interactions that can happen when a photon intercepts vegetation? Upon striking any surface the incoming radiation can be: 1. Transmitted • Some fraction (up to 100%) of the radiation penetrates into and through the certain surface materials such as water 2. Reflected • Some radiation reflects (moves away from the target) and scatters away from the target at various angles depending on the surface roughness and angle of incidence of the rays 3. Absorbed • Some radiation is absorbed through electron or molecular reactions within the medium; a portion of this energy is then re-emitted, usually at longer wavelengths. These three are represented by dimensionless numbers [0,1], but are often represented using percentages. 8. What is the most important and dominant vegetation pigment? Chlorophyll. This is the most important and dominant because low amounts of chlorophyll mean low absorption and reflectance leading to low NDVI which is a sign of an unhealthy plant. High amounts of chlorophyll mean a high NDVI and a healthy plant. Chlorophyll has a unique spectral signature that is highly responsive to red and NIR wavelengths. 9. What colours of light (wavelengths) does this pigment absorb? Chlorophyll absorbs all wavelengths but green. This is why it makes plants green because green is the only color it reflects. 10. What happens to near infrared photons when they intercept healthy vegetation NIR photons are highly reflected by chlorophyll, so with healthy vegetation, they will be reflected more than unhealthy vegetation. 11. What does NDVI stand for? 𝑁𝐼𝑅 − 𝑟𝑒𝑑 𝑁𝐷𝑉𝐼 = 𝑁𝐼𝑅 + 𝑟𝑒𝑑 NDVI stands for the normalized difference vegetation index. It is a method of estimating the overall health of a plant by comparing the levels of measured NIR and red wavelengths. 12. Draw a spectral signatures graph showing reflectance curves for clouds, wet and dry soil, vegetation and water. Include axis labels and wavelength values for the Visible, NIR and MIR (a.k.a. SWIR) regions of the spectrum. The Resolutions 1. Give a definition of spatial resolution. Spatial resolution is the smallest unit of distance that can be determined by a sensor measurement of the target (how much area is represented by a pixel). 2. Give a definition of spectral resolution. The number and dimension of specific wavelength intervals in the electromagnetic spectrum to which a remote sensing instrument is sensitive 3. What are the three components of spectral resolution? • The number of spectral channels/bands used • Their location in the electromagnetic spectrum • The bandwidth of each channel/band 4. Why would Canada want its own receiving station? Canada has 3 receiving stations (Cantley QC, Prince Albert SK, Inuvik NWT). This is beneficial because it allows us to receive data in real-time from polar orbiting satellites for scientific, mapping, weather, surveillance, and other purposes for Canada’s land mass and most of the continental U.S. as well. 5. What are the most recent Landsat satellites? Approximately how long does the Landsat record go back (years or decades)? Landsat goes back into the 1970’s with Landsat 1 being launched in 1972. The most recent Landsat satellites are Landsat 7, 8 and 9. Landsat 7 was launched in 1999, Landsat 8 was launched in 2013, and Landsat 9 will be launched in 2020/2021. 6. Name and generally describe the sensor bands on a satellite with sub-metre spatial resolution. Name three things this satellite is best suited to observe. Finer pixel satellites are often maintained by private sector companies such as Digital Globe’s WorldView satellites. It is often the visible and NIR spectrums that are observed on these satellites to create detailed satellite imagery that firms such as Google will purchase. This fine detail is good for military use, monitoring buildings, urban infrastructure, trees etc. 7. Give two examples of objects or phenomena that can be observed at different spatial resolutions: • 1km: Gives a good image of the atmosphere and oceans, land, earth as a whole. • 250m – 500m: Good for getting a general view of land. • 30m: Forest cover, insect infestations, crop forecasting, wetland erosion. • <1m: Tree based insect infestations, urban mapping, road mapping Active Remote Sensing 1. Explain the difference between active and passive remote sensing. Passive remote sensing measures energy that is naturally emitted – sensing energy that ultimately would be coming from the sun, such as a passive camera system (no flash), or thermal infrared sensors. Active remote sensing is when the systems provide their own source energy for illumination, emitting radiation directed towards a target – the radiation that is reflected back is then measured by the sensor. Active remote sensing could include: LiDAR, RADAR, and SONAR. 2. What are 2 advantages and 2 disadvantages of active remote sensing technologies? Advantages: Weather and sunlight independent, can penetrate vegetation and soil to gain information about surface layers Disadvantages: Power of pulse is low so it can be influenced and interfered by other forms of radiation, there’s limited spectral information, and it is cost-intensive and complicated to analyze. 3. What portion of the EM spectrum is used by RADAR, LiDAR, SONAR? • RADAR uses the microwave portion of the EM spectrum to measure distances. o RADAR is good for detecting metal, water freeze/thaw, salt content, iron oxides, and clay in soils, the size of the wavelength needs to be matched to the size of the surface feature (seen with the XCLP bands in the question below). • LiDAR uses light waves to measure the distance to an object o LiDAR is good for accurate elevation and terrain data, architecture structural information, measuring forest canopy height, identifying plant species. • SONAR uses sound waves to navigate, communicate, and detect objects under the water surface. o SONAR is good for mapping the sea floor, locate fish, detect other vessels in the sea, seismic exploration, and echoscopy. 4. How does the size of the RADAR wavelength being used relate to the size of what RADAR can sense? There are multiple bands (X,C,L,P) used in radar that are good for matching various sizes of objects: X: 2.4 - 3.75 cm, used for mapping and surveillance C: 3.75 – 7.5 cm, used for viewing/penetrating the top layers of vegetation and solids, good for sea-ice surveillance L: 15-30cm, penetrates surfaces, good for observing vegetation surfaces and monitoring ice sheets and glaciers. P: 30-100cm, used for research and experimental applications, this has significant penetration capabilities for estimating vegetation biomass, sea ice, soil, and glaciers. For the exam, you’ll need to know the general size of these wavelengths: X: ~3cm, C: ~5cm, L: ~20cm, P: ~80cm 5. What three key components are used in a LiDAR remote sensing system? 1. GPS system using satellites position to determine the geographic position and height of the sensor 2. Laser system for accurate distance measurement. 3. Altitude measurement using an inertial measurement unit (IMU) to record the precise orientation of the sensor. Canada from Space 1. What percentage of the world’s freshwater lies within Canada? Canada has some 20% of the world's total freshwater resources. 2. What are the 3 areas of Canada that have the most glacial coverage? Nunavut, Northwest Territories, and the Arctic Archipelago. 3. Name and describe 5 of the 15 ecozones in Canada? The 5 ecozones we focused in on class are: Arctic: Above the tree line, most of Nunavut/NWT, many mammals live here such as polar bear, arctic wolf, wolverine. Concerns about the rate of change within the arctic due to climate change (good job for remote sensing to measure). Taiga Shield: Stretches east-west just south of the arctic. It’s a patchwork of wetlands, forests, meadows, and shrublands. Flat or rolling hills with many depressions forming lakes, ponds, wetlands etc. Most human impact is from hydroelectric use and mining. Species of interest include barren-ground and woodland caribou (their habitat is monitored using earth observation). Prairies: The most greatly altered ecozone largely because of agricultural development. Wheat fields, grain elevators, remote farmsteads. Earth observation can monitory cropland health, crop classification, yield estimation, soil characteristics and management, and farming compliance monitoring. Mixedwood Plains (Great Lakes): Has the highest natural biological diversity in Canada: songbirds, reptiles, and amphibians, many migratory birds. It’s also the most populated ecozone, having major Canadian cities such as Toronto and Montreal. There are 5 lakes which are the largest surface of freshwater systems in the world. Earth observation is used to monitor the great lakes ecosystems: higher water temperatures could alter the timing of phytoplankton blooms, different algae development may be detrimental to native species. Boreal Shield: The largest ecozone in Canada – about 20% of Canada’s land mass. 10% of the shield is fresh water. Forest fires are a major disturbance here. Very diverse and productive area in Canada: caribou, lynx, black bear, blue jays. Earth observation imagery can be used here to study wildfire disturbances and evaluate carbon emissions to the atmosphere 4. Describe 3 ways that remote sensing technology can be used to asses Canada’s natural resources. Explained in greater detail above but summarized here: Arctic: measure change in climate, ice levels. Taiga shield: Monitoring of species such as caribou. Prairies: monitoring farm productivity and compliance. Mixedwood Plains: Monitoring the great lake ecosystems and changing water temps. Boreal Shield: Observing wildfire disturbances. 5. Choose one of the following case studies covered in class, and briefly explain how remote sensing was used in the study design: mosaic, barren ground caribou, agriculture, Great Lakes monitoring, fire. Answered in Question 3. Biosphere 1. What is the biosphere? The biosphere is the sum of all ecosystems on Earth, it includes both terrestrial (land) and marine (ocean) ecosystems. 2. What are biomes? Biomes are large naturally occurring communities of flora and fauna occupying a major habitat, e.g. forest or tundra. 3. What is albedo? How much of the light from the sun is reflected? The proportion of the light or radiation that is reflected by a surface. The earth generally has around 29% of light reflected as albedo. 4. What are the inputs to photosynthesis? Energy + 6 CO2 + 6 H2O -> C6H12O6 + 6 O2 Energy, Carbon Dioxide, and Water. 5. What are the inputs to respiration? C6H12O6 + 6 O2 -> Energy + 6 CO2 + 6 H2O Sugar and oxygen. The equation of respiration is exactly the opposite of photosynthesis! 6. How do you measure productivity in the biosphere? • Net primary production (NPP) is the energy stored by plants, GPP is the amount of energy created by plants. o NPP = GPP – respiration energy. • Measure biomass: the dry weight of living organic matter over an area • LiDAR can help measure height of trees. • Eddy-flux towers measure the difference of carbon at ground level to above ground. 7. What is the effect of temperature on the rate of photosynthesis and respiration? Higher water temperature induces water-related stress in plants. Gross and net photosynthesis increases quite a bit and peaks up at around 20°C, past that point respiration will increase exponentially with temperature and decrease the net photosynthesis. Because of this, much of British Columbia has the most productive forests on the planet. 8. Give an example of a carbon source and carbon sink. What causes each example to be a source or sink? Carbon sources: forest fires, harvesting, land clearing. These are carbon sources because they are releasing carbon, but not taking much carbon in. Carbon sinks: new-growth forests and agriculture. They are carbon sinks because they will absorb carbon in the atmosphere to grow, and importantly they are taking more carbon in than is released. Unknown: Forest infected with pine beetle. These trees aren’t 100% alive or dead, it may become a sink after 3 years of attack. Neutral: Old growth forests Cryosphere 1. What does the cryosphere include? The cryosphere includes snow, ice, ice caps and ice sheets, and glaciers. 2. Describe why time series data is useful for understanding glacial changes. Time series data is useful as it provides hard data evidence of historical changes happening in cryospheric conditions (in our glaciers) such as glacial mass balance, glacial extent, sea-ice thickness. 3. List 3 factors that influence the spectral reflectance of snow/ice. The spectral reflectance of snow and ice is dependent on: Grain size, shape, depth, surface roughness, impurities, and near-surface liquid water content. Fresh snow tends to have the highest reflectance, and dirty glacier ice tends to have the lowest. Smaller particles -> greater albedo (reflectance), Larger particles -> smaller albedo. 4. Provide an example of how satellite time series are being used to monitor the cryosphere and how the information collected is pertinent to understanding the cryosphere The freely available MODIS time series data (from TERRA/AQUA satellites) can be used to identify melt ponds on arctic sea ice, track surface features to measure break up and speeds of ice shelf, and measure albedo trends. This information is helpful because TERRA and AQUA have a high temporal resolution (1-2 days), allowing us to get a very full dataset to analyze change in our cryosphere and understand where we are heading under climate change. Landsat has over 40 years of continuous time series observations. 5. What is the difference between Landsat and MODIS imagery compared to RADAR and LIDAR for looking at snow? First, Landsat and MODIS are passive sensor systems and retrieve this data based off reflected sun and thermal data (only works when the sun is shining on the area). Secondly, Landsat and MODIS imagery is freely released and easy to retrieve. 6. Choose one of the sensors covered in class, and explain how it senses cryospheric features and/or phenomena. What are some applications of the data this sensor gathers? • SEASAT o Microwave radiometer – sea surface temperature o Radar altimeter – water levels o IR/Visible radiometers – identify land, water, atmospheric features. o Microwave scatterometer – wind speed and direction o SAR – monitors sea ice conditions o Was only operational for ~100 days, conspiracy. • TERRA/AQUA o Capture 36 spectral bands, have a high temporal resolution and a pixel size 250m – 1km. o Ice sheet trends, breakage and movement of ice shelf • ICESAT o Has the ability to show elevation changes resulting from glacial melt/retreat and snowfall over time. Monitoring Change from Space, Patterns 1. Explain the cyclical, abrupt, and gradual patterns of change. Cyclical change pattern is a pattern that repeats over time. e.g., the change of the seasons, daily tides, tree leaves, the growing and shrinking of sea ice each year (called a seasonal cycle as it occurs annually.) Abrupt change is a rapid shift from one state or condition to another. e.g., forest fires, forest harvesting, land cover/land use change. Gradual change is a slow shift from one state or condition to another, or a trend over time – e.g., climate warming, rising sea surface levels and temperature, slow mortality of trees due to disease/insects, regrowth and reforestation. Afforestation which is a growth there there wasn’t previously – “woody encroachment”. 2. What types of cyclical patterns on Earth can we observe from space? Many cyclical patterns are driven by the change of the seasons, this happens because earth spins on a tilted axis and the sun’s rays will be strongest at different latitudes. Without a tilted axis, earth’s seasonal cycles wouldn’t exist! Some more examples of seasonal cycles include day length, greening and browning of vegetation, animal migration and hibernation, and the times in which we can ski and bike. 3. How do we measure cyclical patterns? (Focus on: Vegetation cycles, Animal migration) With vegetation cycles we measure how green the vegetation changed through the year through use of a phenology camera – which is just a regular RGB camera but we run calculations using this RGB data such as calculating the 2GRBI. 2GRBI = 2*Green – (Blue + Red). Brown vegetation will have a low 2GRBI while green vegetation will have a high 2GRBI. If we plot the 2GRBI for every day of the year there is a pattern, 2GRBI is very low before the leaves come out, it increases sharply once leaves emerge, it remains stable while the leaves are green, and it drops when the leaves change color and die. From there we can identify the 3 key phenology events (question below.) Another way to monitor vegetation cycles is by using MODIS data (daily satellite images, 250-500m resolution), by plotting NDVI just like we did 2GRBI, it will result in a similar plot showing the times of greenup, maturity, and senescence, this helps when we want to analyze broad scale information on the entire planet and use the past information to collect information on how climate change is affecting these areas. With animal migration we use GPS collar data that can determine the location of animals at a specific interval of time, it’s difficult and expensive to do this so usually a small sample is collared. Some examples of GPS collaring is tracking the seasonal patterns of caribou: they move north each summer and return to the same locations to give birth. Leatherback sea turtles migrate from Canada to the tropics each year. Another way to track animal migration is based off citizen science data such as from the eBird mobile app where people record when they spot birds. 4. What are the 3 key phenology events? Greenup: When the leaves emerge Maturity: This is when 2GRBI is at its maximum. Senescence: this is when leaves change color and die 5. What are the 4 data considerations do you need to make when using remote sensing to assess environmental change? Explain each 1. Level of spatial detail - The smallest ground object that can be resolved in the image (pixel size). More detail implies less area covered by a single image and a bigger file size. You will need to match the phenomena to the correct pixel size - Moderate resolution (>25m) is suitable to detect amount of forest lost/gained in an area - Very fine resolution (<1m) is needed to detect changes at a single tree level. 2. Region of the electromagnetic spectrum - Specific regions of the electromagnetic spectrum where the change occurs. - Broad classes such as dead or live vegetation can be separated using very few broad wavelength ranges - More specific classes such as different rock types require comparison of many narrow wavelength ranges. 3. Frequency of re-visit - How often do you need to see an area to characterize the change? - To detect fire scars, a moderate re-visit ~(16 days) is sufficient. - To detect crop green-up or fire progression, something with much higher resolution is needed (daily or hourly). 4. Temporal dimension - How long do you need to collect data to be able to characterize the image? - This varies with the scope of study for example changes in climate are slow and thus require long term information (>10 years). Area burned after a fire is a fast change and requires shorter term information. We have aerial/photographic imagery from the past 85+ years, satellite for only the last 40 years. Cyclical patterns, abrupt and gradual changes 1. Label the following changes as cyclical, abrupt, or gradual a. Animal migration - cyclical b. Broadleaf phenology - cyclical c. Decline in forest health - gradual d. Fire - abrupt e. Flowering of plants - cyclical f. Shift north in animal range due to climate change - gradual g. Insect damage (such as mountain pine beetle) - gradual h. Land conversion from forest to a road - abrupt i. Reforestation following the abandonment of a city block - gradual 2. Which spectral signature might you see before a fire, and which might you see after a fire? 3. What data source is best for locating active fires? a. Landsat data b. Camera time-lapse data c. MODIS temperature data d. GPS data C. MODIS temperature data. 4. What data source is best for mapping the total area burned in a year across British Columbia? a. Landsat data b. Camera time-lapse data c. MODIS temperature data d. GPS data A. Landsat data. 5. What is the easiest way to distinguish fire and harvest disturbances using Landsat imagery? a. Spectral signature b. The size and shape of the disturbance c. The duration of the disturbance d. The forest regrowth following the disturbance B. The size and shape of the disturbance, because fires usually have irregular perimeters and occur over large areas. Harvesting has regular shapes and occurs in small areas 6. What data would you use if you wanted measure phenology for the whole planet in 2015? a. Camera time-lapse b. Landsat data c. MODIS data d. GPS data C. MODIS data - because MODIS has a temporal resolution of 1-2 days, allowing you to plot the phenology change over the year. Landsat is too slow for this. 7. What data would you use if you wanted to measure the phenology of specific trees in your backyard? a. Camera time-lapse b. Landsat data c. MODIS data d. GPS data A. Camera time-lapse Label the following patterns/changes as plant phenology, fire, insect disturbance, land conversion (forest converted to a road), or reforestation. Fire Land conversion Plant Phenology Insect disturbance Reforestation 8. Label the points on the phenology curve as maturity, senescence, or greenup Green point – greenup Blue point – maturity Red point - senescence 9. How can you calculate the growing season length from satellite imagery? a. Length of time between greenup and maturity b. Length of time between greenup and senescence c. Length of time between maturity and senescence B. The growing season is the length of time between greenup and senescence. 10. True or false: When a broadleaf tree puts on leaves in the spring, more blue and red light is absorbed by the tree True, leaves will absorb all light on the visible spectrum besides green 11. Which of the following is an example of land conversion? a. Forest harvesting b. Forest fire c. Clearing a forest for agriculture C. 12. Which disturbance moves large amounts of carbon into the atmosphere immediately? a. Insect disturbance b. Forest harvest c. Forest fire d. Forest clearing to build a road C. 13. Which disturbance only affects specific tree species? a. Insect disturbance b. Forest harvest c. Forest fire d. Forest clearing to build a road A. 14. An outbreak of which insect in BC affected > 18 million hectares and killed > 700 million cubic metres of timber between the 1990s-2000s? a. Western spruce budworm b. Tent Caterpillar c. Eastern spruce budworm d. Mountain Pine Beetle D. 15. Describe how you could use GPS data to protect the migration path of caribou in Canada. We can use the GPS collar data to see where caribou tend to migrate through the cyclical changing of the seasons. We can use this data to protect the migration routes caribou tend to visit more often, and limit any disturbances in these areas. 16. How can you use GPS data to determine where and when wolves are eating prey? Wolves tend to move a lot when they are hunting and then have little movement when they are eating. This would be an abrupt change. We would see in the GPS data that there will be a cluster of wolves not moving very much at the kill site (eating their prey), and then they will start moving again until the next kill site. 17. Do insect outbreaks appear gradual or abrupt in satellite imagery? Explain why. In satellite imagery, insect outbreaks will often appear abrupt in satellite imagery due to the large pixel size in a lot of remote sensing applications. By the time a significant change in the forest has occurred due to an insect infestation, it is already quite far into the outbreak, and the pixel colors will change all at once versus gradually if we were to see a larger amount of detail such as in a ground-level camera or fine pixel private satellite. 18. Describe how you can tell the difference in satellite imagery between a forest harvest and an area that was cleared to build a neighborhood. A forest that has been harvested will show a significant drop in NDVI followed by a gradual increase as regrowth appears. A forest that has been cleared to build a neighborhood will too have a significant drop in NDVI but will remain at this dropped level because no regrowth is occurring (land use has changed). Observing the Human Footprint 1. What is the human footprint and what indicators of the human footprint are commonly assessed using remote sensing? The Human footprint is a geographic extent of land under human use, a measure of how much we are using the Earth’s natural resources, and a metric that allows us to calculate human pressure on earth. It can be assessed by the size of the population, the amount of human settlements such as cities, and the degree of resource extraction such as deforestation, oil extraction, and mining. It’s a global phenomenon and is changing every day but there’s no universal definition for it, and there’s an absence of a detailed data source with global coverage. 2. Why is aerial photography a good way to assess the impact of human development? Aerial photography and remote sensing is a good way to assess the impact of human development because it helps us avoid confusions defining what a footprint is, it offers a consistent measurement over time and space, and enables iterative revisiting and measurement at a global extent. This photography allows us to answer questions on urban morphology, urban growth, traffic monitoring, and assessment of populations. Aerial photography in particular has been around longer than satellite imagery so it gives us the longest available record of landscape change (~90 years), it works well has a comparative investigation with more recent satellite imagery. 3. How can nightlights be related to the human footprint? Using what socio/economic variables? We can detect city lights, gas flares, and fires by analyzing nighttime lights data collected from satellites such as DSMP-OLS and the newer VIIRS. It provides an interesting perspective on the spread of humans across the earth. Since it has such a high coorelation to human activities, it is used to measure population, energy consumption, economic activities such as GDP, urban extent, gas flaring volume, and CO2 emissions. 4. What might you expect to see from a nightlight image of western Canada? The southern portion is more populated so I would expect to see a higher amount of light there, with less density of light outside of the urban regions. Observing the Earth using Big Geo-Data. 1. What is a definition of big data? Extremely large data sets that may be analyzed computationally to reveal patterns, trends, and associations. It’s data that is expanding and growing at a high rate that the only realistic way to manage and analyze it is by use of computers. 2. What is the difference between data, information, and knowledge? Data – “things given” in Latin, facts and descriptions of the world we are living in (i.e. this tree is 20m tall) Information – recorded data or captured facts (i.e. an image) Knowledge – organized information (i.e. a map) 3. What are the 4 “V’s of big data? Give an example of how each of the 4 “v”s can be related to remote sensing big data. 1. Volume The main characteristic that makes data “big” is the sheer volume. The total amount of information is growing exponentially every year. Close to 900 exabytes and would grow by 50 percent every year. No one really knows how much new data is being generated, but the amount of information being collected is huge. 2. Variety With application to CONS 127, there’s many different types of remote sensing data that is collected. Active sensor – information is obtained by transmission and reception of radio waves , such as: LiDAR, Microwave, Radar Passive sensor – information is obtained by reception of natural origin (e.g. sunlight), such as Cameras, Imagers, Spectrometers 3. Velocity Velocity is the frequency of incoming data that needs to be processed. Think about how many SMS messages, Facebook status updates, or credit card swipes are being sent on a particular telecom carrier every minute of every day, and you’ll have a good appreciation of velocity. 4. Veracity (Uncertainty), Veracity refers to the trustworthiness of the data. Can the manager rely on the fact that the data is representative? Every good manager knows that there are inherent discrepancies in all the data collected. Remote sensing data can be used to ground truth existing maps and confirm their accuracy. Remote sensing data can be used as an audit tool to assess if changes in management were in fact undertaken. Move towards dynamic monitoring of illegal logging in tropical countries which can then be compared to national estimates of timber lost. 4. Describe one big data network in detail: What remote sensing datasets does it use? What qualifies that network as a Big data Network? Meteorological networks There’s a huge volume of meteorological data from many locations and sources such as governments and private sector. All of this data is coming in at a fast velocity as weather measurements are taken and recorded at very close intervals. The data comes in a large variety because of the many locations and forms of weather measurement such as surface, marine, upper air, aircraft, satellite, and weather radar observations. This data is veracious because there is so many extraneous measurements being made that allows us to fact check and verify any given measurement. 5. What forms of meteorological observations are there? A bit more detail on the different forms of weather observations: Marine Observations • Record sea surface temperature, wave height/period • Voluntary Observing Ships (VOS): ~4000 observing ships (25% record on a daily basis) • Drifting Buoys recording around 27,000 sea surface termperatures every day Surface Observations • ~ 11,000 weather stations around the globe, collect data at least every 3 hours. • Commonly recorded data are: Temperature, Humidity, Atmospheric pressure, Wind velocity. Upper Air Observations • ~ 1,300 upper air stations, mostly using balloons up to 30 km from the ground • ~ 100 to 200 of these stations collect daily records • Commonly use balloons with a radio transmitter—radiosonde with onboard GPS units that collects a vertical profile of the lower atmosphere up to 35 km. o These have a questionable sustainability as many of these balloons and their expensive equipment are difficult to recover after they pop, falling into oceans, mountain ranges, and private property. Aircraft-based Observations • ~ 130,000 observing aircraft including commercial airlines • Since 1979 automatic reports of basic meteorological variables and turbulence at cruising level • Participants in US including 6 major commercial airline– American, Delta, FedEx, Northwest, United, and UPS. Canada: Air Canada and WestJet. • However, as aircraft do not fly when major storm occurs, there is often a gap for collecting data of extreme weather. Satellite Observations • Monitors water, weather, and climate using visible and NIR images. • Currently 15 functioning satellites and 33 planned satellites (up to 2030) The Future of Observing the Earth from Space 1. Explain some of the future planned satellite missions • Landsat 9 will be launched in 2020 and will have similar specs to LandSat 8. With each Landsat mission, the sensors become more sensitive and see more detail 2. 3. 4. 5. 6. o Future Landsat missions may become smaller and more specialized. • The European Space Agency Sentinel Series of satellites have 6 satellites. Weather RADAR and “land services” multispectral satellites have been launched already – this data is publicly available and complements Landsat data.. Planned satellites include ocean and land monitoring (multiple instruments), atmospheric composition monitoring, and global sea surface height for climate studies using RADAR. • LiDAR satellites such as the Geoscience Laser Altemeter System (GLAS) or the Global Ecosystem Dynamics Investigation Lidar (GEDI) help provide global high-res (25m footprint) LiDAR data. • Constellation satellites are a group of satellites that work together, such as the continued development of the Galileo GPS system, or Internet satellite constellations What are the future trends of satellite missions? The trend of future satellite missions is that they are now going to become smaller and more specialized such as future Landsat missions and the LiDAR specific satellites. Many more satellites will start to be developed by the private sector and not just by government programs such as SkyBox and Urthecast. What, in your view, is more important: data continuity with new versions for old programs, or new, innovative satellite programs? (Why not both?) I believe that we should pursue new and novel satellite programs and attempt to do things never done before with satellites. However the measurements given by old programs are still valuable and continue to be valuable as we need to measure change and compare with past data, so it is also important to continue to support the measurement of this kind of data. If I had to pick one option, I would choose data continuity because it is very important we continue to compare future data to the past. What is a constellation network of satellites? As written above, constellation satellites are a group of satellites that work together, such as the continued development of the Galileo GPS system, or Internet satellite constellations. To me this seems like the next logical step as we make our satellites smarter by connecting them. What are two benefits and two downsides of Google deciding to blur certain locations in Google Earth? What do you think about their decision to blur locations? Benefits - Protect the security of sensitive areas such as military defense bases and prisons - Prevent groups with malicious intent from making use of such imagery Downsides - Makes it questionable whether or not the skies are really open. - Could encourage even more censorship by governments, degrading freedom (before you know it, every government building may be censored) My opinion: I fully understand why they have decided to blur locations and there are very real reasons for doing so such as protecting national security and avoiding malicious attacks. However, there is so much satellite imagery data available nowadays I am not sure if enforcing this blurring is even feasible. Google Maps blurs this area? Okay, I will go to Bing, OpenStreetMap, Apple Maps, or some other database that likely has an uncensored image of what I want to look at. What are some issues associated with small cube sat programs? These cubesats have variable quality of sensors and may not be good enough to compare between different satellites. These are also built from off-shelf sensors that may not be built with durability in mind, these cubesats only remain up for around a year so there’s a question of sustainability as these boxes won’t last forever. These are also much cheaper to setup and launch, resulting in more of these being launched, creating more possible space junk. 7. If you were to build a satellite, what things in class that you have learned give you an idea of an application, how would you go about making it work? Now with innovations such as SkyBox cubesats, it’s easier than ever to have our own satellites built and placed into orbit. One form of satellite we could launch is to build one for monitoring any space we want such as agriculture or insurance modelling. We could source more easily available sensors to place into our box and then rely on NASA or private companies to launch these cubesats into space. 8. Why should we care about sustainability of space science programs? One issue we face with space satellite programs is how we are going to manage space-junk once these satellites fail and/or get destroyed in collisions. We could render our orbits nonfunctional within a few years if we do not manage space junk and build our space programs with sustainability in mind. This could result in societies in the future not being able to use any space technology that we benefit from today such as GPS because our orbits have become too polluted to function properly. So we should absolutely care about the sustainability of these programs to ensure future generations get to benefit from and innovate upon these technologies.