Question 1 Image Detail and noise detection

[Part 1]  Explaination of Noise in Each Band

In the Original image, there are five bands. Due to the fact that these five bands are not in order, there, users has to make sure which band is which. Band 1 is TM1, band 2 is TM2, band 3 is TM3, band 4 is TM4 and band 5 is TM5.

[Noise]

The noise is particularly visible over homogeneous surfaces such as clouds and  waterbodies. In addition to the Atmospheric noise, Band 1 (TM1), band 2 (TM2) and band 3 (TM3) are experencing some atmospheric noises and sensor artifacts. But band 4 and 5 do not have any noises and artifacts.



TABLE 1-1  it shows which band contains what types of noise,

and this has discripstions of each noise that each band has.



Click the Table for Larger View

 



      

  

  

 

     

  








     To see the original image, click images

[Part 2] Details of Noises in Each Band

                           

[Part 3] Types of Noise

Coherent Noise

     Coherent Noise (CN) appears as a repeating pattern in satellite imagery. CN is most visible over dark homogenous regions. These patterns may appear in only one band or in several bands and may or may not be phase-locked to the instrument scan time. Although CN can be corrected, this correction often degrades other parts of the image, so correction is performed only for very high magnitude noise sources. Currently, no CN correction is performed for Landsat 5 Thematic Mapper (TM) or Landsat 7 Enhanced Thematic Mapper Plus (ETM+) Level 1 products, except for Nyquist Noise (described below).

     CN can arise from many electrical systems onboard the satellite, including the power supply, the detector circuitry, and every electrical system in between. All satellites have some CN sources that appear at a certain frequency and magnitude. These noise sources are often discovered before launch, but they may change over the life of an instrument. If significant changes occur, or if new CN patterns appear that were previously unseen, they may be cause for concern and further analysis. (Source: UGUS)

      Coherent noise (CN) is a low-level periodic noise pattern present in all Thematic Mapper imagery. It is most obvious in homogeneous regions such as water and desert areas. The periodic components are generally quite stable in terms of their period or frequency. In some cases, the phase of the component is also stable. (Source: PCI informaion)

Bit-Flip Noise

Bit-Flip Noise is a specialized form of IN that causes single-pixel shifts in the data that are set powers of 2—a pixel may be 128, 64, or 32 DN higher or lower than its actual value. (Smaller shifts occur—16, 8, 4, and 2 DN—but are generally too small to see.) This artifact arises from some digital source, often a transmission error or a problem in the ground processing systems. Unlike most sources of IN, Bit-Flip Noise is often correctable.(Source: UGUS)

Memory Effect

Memory Effect (ME) has been known by various names such as “banding,” “bright target recovery,” “bright target saturation,” “scan-to-scan striping,” and “radiometric hysteresis,” Thematic Mapper data often has the Memory Effect. By observation, it has alternating lighter and darker horizontal stripes that are 16 pixels wide in data that has not been geometrically corrected. These stripes are most intense near a significant change in brightness in the horizontal (along scan) direction, such as a cloud/water boundary. ME appears in Bands 1,2,3 or 4. (Law Y.N., 2000)

REFRENCE

Law, Y.N. 2000. Landsat 7 ETM+ Coherent Noise Characterization and Correction, South Dakota State University, Retrieved from http://iplab2out.sdstate.edu/Thesis/thesis/Law_Thesis.pdf