our green and blue planet, remote sensing Flashcards
remote sensing
= the science of obtaining information about objects and areas from a distance, typically from aircrafts or satellites
- originally for military purposes
- satellite resolution and coverage has increased over time
Landsat satellites
- first non military earth monitoring satellite NASA 1972
ESA satellites
- european space agency
- sentinel satellites take pictures of almost everywhere on earth every 5-6 days
radiation sensors, vegetation
- sensors can measure radiation, break down light reflected into bands of certain wavelengths
- false colours can be added to satellite images
- leaves absorb most visible light, especially blue and red
- Vegetation appears green because leaves absorb less in the green region of the spectrum
- leaves reflect ~50% near-infrared (high reflectivity of high wavelengths)
- immediate contrast between the absorbed visible light and the reflected near-IR gives a distinctive ‘red edge’ to the spectral signature of vegetation detectable by satellites
- reflectivity depends on the species, identification is possible
measuring NPP at a global scale
- NPP = net primary productivity, amount of carbon uptake
- subtract plant respiration (RES) from gross primary productivity (GPP)
- measured in kg/C/m^2/y
- figure out potential for carbon sequestration and hotspots for carbon uptake
GPP
= gross primary productivity, the total rate at which an ecosystem captures and stores carbon as plant biomass for a given length of time
global NDVI
= normalised difference vegetation index
- assesses whether the surface contains live green vegetation or not, calculated from the difference between the level of reflectivity between red and near infrared bands
- useful for calculating rate of growth, senescence (tracking phenology) and ocean productivity
monitoring coastal upwelling of phytoplankton via chlorophyll concentration
- algal blooms can be toxic
- chlorophyll concentration can be monitored by satellite images
- productivity and therefore chlorophyll concentration linked to upwelling as upwelling increases nutrient availability
monitoring sea surface salinity
- influenced by rainfall, evaporation, river estuaries and melting
- movement and mixing of water can be monitored
monitoring environmental change
- historical remote sensing images
- clear evidence and documentation of changes such as glacial retreat and coastal erosion
wildfire detection
- useful for large uninhabited landscapes, high latitude areas can burn indefinitely (peat) without detection
- infrared heat sensors detect abnormal heat sources
- probability of spread can be estimated from neighbouring land cover and soil moisture content
detecting soil moisture
- can be combined with weather data and hydrological models
- flooding and vegetation growth predictions
remote sensing of biodiversity
- using satellites, aircraft, drones, UAV, citizen science (phone images), camera traps, sound recorders, transmitting collar, eDNA collection
- combining satellite data with GPS collars to track migrations, show animal behaviour and evolution
- computer algorithm trained to automatically detect surfacing whales from satellite imaged
- monitor species indicators such as habitats/vegetation/landscape
GB LCM
- first digitised land cover map of UK in 1990s
- increased in resolution since
- still made substantial use of ground cover surveys
- showed agricultural production, integration of urban systems into landscape
national vegetation classification
- describes different types of habitats by identifying vegetation
- phase 1 map of Wales, identified different habitats and therefore animals associated with them, integration of satellite images, measures of terrain/topography etc
3D remote sensing
- LIDAR systems = light detecting and ranging
- send out pulses of lasers and measures time it takes reflected light to come back to sensor
- high resolution topographic maps
- estimation of carbon storage from biomass and tree height
- reliant on clear sky conditions
measuring environmental pollutants
- eutrophication (algal bloom) from organic pollutants increase turbidity of water (chlorophyll and absorbed organic carbon)
- track source and predict movement of pollutants
identifying disease vector hotspots
- malaria, anopheles mosquito
- larvae need source of standing water
- use off the shelf drones (cheaper) to identify larval habitats
- in future drones may automatically drop larvicide into water pools
future of remote sensing
- more sensors, more computing power
- higher resolution, more detailed images, more accurate differentiation and analysis
- easier to use software, large scale data
- arcGIS
european sentinel satellites
- publically funded, data free to access
- Sentinel 1, land and ocean monitoring
- Sentinel 2, land monitoring
- Sentinel 3, marine observation
- Sentinel 4, air quality monitoring
- Sentinel 5, atmospheric monitoring
- Sentinel 6, oceanography and climate change monitoring
COBWEB project
integrates survey data collected by the public on smartphones, EU, in UNESCO sites
georeferencing
- assigning real world coordinates to data
- facilitates machine learning
