Yes Flashcards
What are the three pillars of modern Geodesy/ requirement of consistent reference system?
Geometry and Kinematics
Rotation and Orientation
Gravity Field
What are the advantages of classic photogrammetry?(5)
Contactless Measurements
Large range of sizes
Short time of Observation
3-D analysis
Extensive Documentation
What are the cons of classic photogrammetry?(3)
Sufficient Illumination required
Sufficient Visibility Required
Expensive Technology
What are the 3 types of data acquisition?
Terrestrial, Aerial, and Satellite
What are the four types of images?
Single Image (Orth projection)
Image Pair (Stereo Triangulation)
Image Block (Block Triangulation)
Image Sequences (Movement)
What are the three technology levels of Photogrammetry?
Analog, Analytical, and Digital
What is a necessity for ortho image generation?
A surface model
What are Vector Products / Orthophoto useful for?
Map updates and plotting of sealed areas
What is DTM and what is it useful for?
Digital Terrain Model, useful for wire frame representation, 3d Visualization and height variation
What is the pinhole camera defined by?
Interior orientation
- Calibrated Focal Length
- Perspective center
What are three important features of working of pinhole camera?
Image rays are straight lines
Perspective center as point
Image points in a plane
What are some model errors for pinhole cameras (5)?
Distortion
Blurring caused by diffraction
Lens errors
spherical aberration
chromatic aberration
Blurring caused by motion
Filter / Color
How much larger is minimum recognition size usually?
4 - 5 times the GSD
How do you reduce radial displacement?
Bigger calibrated focal length
What are direct geo-references?(6)
Directly measuring position and altitude
GNNS Global Navigation Satellite Systems
Inertial Measurement Units IMU
Star Tracker
Position is fixed in parallel data acquisition
Synchronization Necessary
What are Indirect Geo References? (5)
Computing absolute position from image data
Spatial Resection / Bundle Block adjustment
Needed are known points and Ground Control Points
Position is computed in post-processing
Sufficient amounts of known points neccessary
What is photogrammetry?
The science of obtaining reliable information about the earth and its environment using non-contact sensors.
What are analog ariel images useful for?
Updating building footprints
What is GSD useful for?
For getting an estimation of the resolution of the system
What is swath width important for?
Satellites
What is Remote sensing and Earth Observation?
The science of acquiring information about the earths surface without being in contact with it
What are the two types of sensors with examples?
Passive sensors that don’t emit radiation: Multispectral Sensor, Hyperspectral Sensor
Active sensors that emit radiation: LIDAR sensor, Radar Sensor
What are the three resolution trade offs?
Spectral
Geometric
Temporal
What are some EO Satellite Missions? (Optical) (7)
Nasa: Landsat
ESA: Copernicus Sentinal-2
Digital Globe: Geo-Eye
Planet: RapidEye/SkySat
Sentinal-5
DLR DESIS
EnMAP
What are the types of scattering?(3)
Single Bounce
Double Bounce
Multi Directional
What are some Radar EO Missions?(2)
ESA: Copernicus Sentinel-1
TerraSAR-X
What are some LiDAR EO Missions?
ICESat-2
ESA: Aeolus
What are Soma Applications of EO?
Environmental monitoring
Agriculture and Vegetation Modeling
-Disaster monitoring
Climate change modeling Monitoring water balance mapping informal settlements
What are the Working Principles of a Laser Tracker?
Detect Reflector
Measure angle and distance
Follow Reflector when moving
What is a technique in inferometry?
Using 2 frequencies
What is a measuring arm
Measuring arm with contact or no contact triangulation scanner
What are the steps for quality inspection?
Data acquisition
Data pre-processing
Processing target values
How do beats relate to range in measurement of time of flight?
Beats = 2 range
What is the summary of TOF?
Longer range, no reflector needed
What is the summary of triangulation?
Higher accuracy, no reflector but only close ranged
What is the summary of Interferometry?
Highest accuracy, mid range, reflector needed
What is IMU?
Inertial measurement unit
What is LiDAR
Light detection and ranging
What does Geometry and Kinematics include?
Point Positions
Deformations
Sea Surface
What does Gravity Field Include?
Static
Time Variable
What are some important atmospheric variables?
Surface Pressure and Surface Precipitation
What are some important Oceanic Variables?
Surface Sea Level, Surface Current, Sub-Surface Current
What are some important Terrestrial Variables?
River Discharge, water use, groundwater, lakes, glaciers and ice caps, ice sheets, terrestrial water storage, moisture
What are properties of terrestrial data bases? 3
Hetrogeneous data distribution
Hetrogeneous accuracy
Contain high-frequency signals
What are properties of Altimetric graivity databases 3
Alternative method to derive gravity from mean sea surface with MDT corrections
Covers oceans
Contains high frequency signals
What are key observables for SST in high-low mode?
GPS orbit
What are key observables in SST low-low?
Inter-satellite ranging
GPS orbits
What are key observables in Satellite Gravity Gradiometry?
Gravity gradients
GPS orbits
How is gravity measured using satellites?
Satellite orbits
satellite orbit differences
acceleration differences
What are properties of SST high-low?
physical quantity (gravity) derived from geometric quantity (orbit perturbation)
not direct functional of gravity potential
highly non-linear
What measurement principle does GRACE use?
SST low-low
16
q
What is one use of Satellite Altimetery?
Global Monitoring of sea level
What are the requirements for highly accurate measurement of sea level?
Highly accurate measurement of distance
Highly accurate Measurement of Satellite Orbit
How can Satellite orbit and distance of satellite from sea level be measured?
Satellite Laser Ranging (SLR)
and
Radar Altimetery
What is an alternative methods for determining satellite height?
Doppler Orbitography (DORIS)
Global Navigation Satellite Systems (GNSS)
What is GGOS?
Global Geodetic Observation System
What is an important GGOS Core Sites?
Geodetic Observatory Wettzell
What is ITRS
International Terrestrial Reference System
What are some uses of ITRS?
Global positioning/navigation
Surveying and mapping
Geo-referencing
What is ITRF
International Terrestrial Reference Frame
Name four parts of the ITRF
Radio Telescopes
GNSS Stations
Satellite Ranging Stations
Doppler Antennas
What id target accuracy of ITRF?
1mm for position
-0.1 mm for change of position/year
What are some Scientific Applications of GNSS
Plate Motion
Continental Drift
Earthquakes
What is TRANSIT and when was it developed?
Doppler based satellite navigation system, 1958
What is NAVSTAR Global Positioning System
Important Program in history of GNS
How is signal travel time determined??
By replicating the satellite code sequence on the local device
What is the basic setup of the GPS constellation?
6 orbit planes
4 satellites per orbit
about 20,000 km height
Name GNSS Systems of each nation
GPS - Merica
GLONASS- Russia
Galileo - EU
BeiDou - China
How many GPS satellites does the U.S. have ?
32
What in Interoperability?
Signals from different systems being used together
What is compatibility?
Signals from different systems designed so they don’t interfere with each other
What is integrity?
Measure of correctness of system
How can different signals differ?
Modulation: energy and polarization
What are the parts of the Earth System?
Lithosphere, Biosphere, Cryosphere, Hydrosphere, Atmosphere
How are the dynamics of the atmosphere described?
The Navier-Stokes Equations
What is the hydrosphere?
Liquid surface and subterrean water
What is the cryosphere described by?
Approximate laws eg. Glenn’s law
How is the temperature of the earth determined?
Balance between ingoing and outgoing radiation
What determines earths temperature?
Orbital eccentricity
Changes in tilt / obliquity
Axial precession / wobble
