Topic 4: Altimetry Flashcards
Altimeter
uses time delay relationship to range distance with great accuracy
measure surface topography
spaceborne altimeter have:
satellites
Nadir facing censor
orbit system
data processing system
two types of Altimeters
Radar and Laser
what is ICESat
a satellite laser altimeter that was used to measure ice
what two variables are required to measure altimetry
Time and range
what are two other measurements for altimetry
- intensity, called backscatter
- waveform. complex and difficult to interpret
what is footprint
the coverage a satellite has over the ground.
error sources of Altimetry
- satellite position
- atmospheric effects
- deriving true-height from a radar waveform.
how is sea level determined
With altimetry
two contributors to SLR
- thermal expansion
- freshwater addition
what is the current largest contributor to SLR right now
small melting terrestrial glaciers
ice sheets and sea ice are measured with what remote sensing device
Altimetry
ICESat -2
- Laser Altimeter
- raw data
- gridded surface height
how is sea ice thickness measured
Its only estimated, using archimedes principle. its measure using Altimetry
what is freeboard
freeboard is the amount of ice that is above the surface of water. must be floating
ice freeboard measurements with radar and Laser
snow sits on top of ice most of the time. having huge impacts on estimates.
- lasers cannot penetrate snow, therefore the overestimate freeboard
- Radar does penetrate snow but is less precise.
what is saline snow
its salty snow that is created when an ice frees it sends salt to the surface. this effects active sensor measurements as it impacts backscatter
what are other applications of Altimetry
Geodesy
tsunamis
large scale ocean circulation patterns
climate, el ninio
lake/river level monitoring
