Lab 3 Flashcards
What regions of the electromagnetic spectrum are useful for remote sensing?
ultraviolet or UV,
the visible spectrum (i.e., blue, green, red),
reflected and thermal IR,
and microwave.
What is the difference between atmospheric scattering and absorption?
Scattering occurs when particles or large gas molecules present in the atmosphere interact with and cause the electromagnetic radiation to be redirected from its original path. Absorption is the other main mechanism at work when electromagnetic radiation interacts with the atmosphere. In contrast to scattering, this phenomenon causes molecules in the atmosphere to absorb energy at various wavelengths.
What is the difference between specular and diffuse reflection?
When a surface is smooth we get specular or mirror-like reflection where all (or almost all) of the energy is directed away from the surface in a single direction. Diffuse reflection occurs when the surface is rough and the energy is reflected almost uniformly in all directions.
What is the difference between passive and active sensors?
Passive sensors can only be used to detect energy when the naturally occurring energy is available. For all reflected energy, this can only take place during the time when the sun is illuminating the Earth. Active sensors, on the other hand, provide their own energy source for illumination. The sensor emits radiation which is directed toward the target to be investigated. The radiation reflected from that target is detected and measured by the sensor.
Typically, how wide are satellite imaging swaths?
Imaging swaths for spaceborne sensors generally vary between tens and hundreds of kilometres wide.
For satellite images, generally speaking, what’s the relationship between resolution and ground area coverage?
Sensors onboard platforms far away from their targets, typically view a larger area, but cannot provide great detail.
What is spectral resolution?
Spectral resolution describes the ability of a sensor to define fine wavelength intervals.
In terms of satellite data, what is temporal resolution?
The revisit period of a satellite sensor is usually several days. Therefore the absolute temporal resolution of a remote sensing system to image the exact same area at the same viewing angle a second time is equal to this period.
What portions of the electromagnetic spectrum were included with the Landsat TM sensor that were NOT included with the MSS sensor?
Blue, shortwave and thermal IR bands are included with TM but not with MSS.
Why are there two identically-named “Clip” tools? Which toolboxes are they in?
One is for vector (Analysis Toolbox) and the other is for raster (Data Management Toolbox)
Why would you want to combine single raster datasets into multiband raster datasets?
The following are some examples of why you would want to combine single raster datasets into multiband raster datasets:
1. You may have received some satellite data where each band of data is contained in a
single file—for example, band1.tif, band2.tif, and band3.tif. To render these raster
datasets together to create a color composite, each band needs to be contained within a single raster dataset (for example, allbands.tif).
- You may have several raster datasets of the same area captured at various times. By
displaying these raster datasets as a color composite, you can detect change in the area, such as urban growth or cut forests. To create this color composite, each raster dataset needs to be contained as individual bands within a single raster dataset. - In some cases, the output of an analysis operation is a single-band raster dataset. To do
further visual analysis, you may need to combine the outputs by rendering your data as a
color composite. - Combining bands into one raster dataset can help you organize many related single-band rasters
What are the four resampling techniques? What type of data are each of the resampling
techniques primarily used for?
There are four options for the Resampling Technique parameter:
Nearest—It is used primarily for discrete data, such as a land-use classification, since it
will not change the values of the cells.
Majority—It is mainly used with discrete data just as the nearest neighbor method;
Majority tends to give a smoother result than Nearest.
Bilinear—It is useful for continuous data and will cause some smoothing of the data.
Cubic—It is appropriate for continuous data, although it may result in the output raster
containing values outside the range of the input raster.
What are pyramids?
Pyramids are reduced-resolution representations of your dataset and are used to improve
performance.
What pixel types are not compatible with raster attribute tables?
It is not possible to build a raster attribute table for a raster dataset that is a pixel type of 32-bit point
When are statistics required for a raster dataset?
Statistics are required for your raster and mosaic datasets to perform certain tasks, such as applying a contrast stretch or classifying your data.
