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-**Figure 3.** An example interferogram from StaMPS processing, spanning nearly one year from September 1997 to August 1998.\\  A clear relationship between phase or range change and elevation can be seen in this interferogram indicating contribution from the atmosphere. Velocities are in the Line Of Sight with red (positive) moving towards the satellite and blue (negative) moving away from the satellite.
+**Figure 3.** An example interferogram from StaMPS processing, spanning nearly one year from September 1997 to August 1998.\\  A clear relationship between phase or range change and elevation can be seen in this interferogram indicating contribution from\\  the atmosphere. Displacements are in the Line Of Sight with red (positive) moving towards the satellite and blue (negative) moving\\  away from the satellite.
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-However, there is still much uncertainty about what physical features on the edifice the persistent scatterers correspond to. While it may appear that there is a distinct signal of uplift just off-center of the volcano, there is good reason to believe that the presented results are heavily influenced by atmospheric effects. In several of the interferograms created through StaMPS processing, a strong correlation between phase and elevation was present (Figure ##), indicating influence from atmospheric changes.
+**Figure 4.** Final StaMPS result showing average velocities over the time period of 1996-2002. Apparent uplift signal just\\  west of the crater is likely an artifact of the atmosphere removal process. Velocities are in the Line Of Sight with red \\ (positive) moving towards the satellite and blue (negative) moving away from the satellite.
+However, there is still much uncertainty about what physical features on the edifice the persistent scatterers correspond to. While it may appear that there is a distinct signal of uplift just off-center of the volcano, there is good reason to believe that the presented results are heavily influenced by atmospheric effects. In several of the interferograms created through StaMPS processing, a strong correlation between phase and elevation was present (Figure 5), indicating influence from atmospheric changes.
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-In generating the velocity map shown in Figure ##, a tool within StaMPS was used to try and estimate the atmospheric contribution to phase. This tool takes advantage of the fact that the atmospheric contribution to Interferometric phase, is often correlated with terrain elevation. Plots of phase versus elevation are displayed for each interferogram, and the user decides whether and how to fit a line to the data (Figure ##). The linear fit to the data is used to create an atmospheric phase mask which is subtracted from the interferogram after unwrapping phase. In some interferograms, however, the relationship between phase and elevation is less clear (Figure ##), and deciding how or whether to fit a line at all can be subjective, difficult, and substantially impact the final results.
+**Figures 5 (left) and 6 (right).** On the left is an example plot of unwrapped phase vs elevation for an interferogram heavily influenced by the atmosphere. The red line fit to the data is used to create and remove an atmospheric phase screen. On the right is an example of when fitting a line to the phase-elevation data may be subjective or not fully representative of the atmosphere in the interferogram.
+In generating the velocity map shown in Figure 4, a tool within StaMPS was used to try and estimate the atmospheric contribution to phase. This tool takes advantage of the fact that the atmospheric contribution to Interferometric phase, is often correlated with terrain elevation. Plots of phase versus elevation are displayed for each interferogram, and the user decides whether and how to fit a line to the data (Figure 5). The linear fit to the data is used to create an atmospheric phase mask which is subtracted from the interferogram after unwrapping phase. In some interferograms, however, the relationship between phase and elevation is less clear (Figure 6), and deciding how or whether to fit a line at all can be subjective, difficult, and substantially impact the final results.
 StaMPS processing of SAR data over Mount St Helens identifies pixels with low phase noise on the edifice and within the crater. This indicates that there is promise for Persistent Scatterers processing techniques like StaMPS to overcome decorrelation due to snow and trees and potentially image pre-2004 eruptive deformation. However, because of the possibility that StaMPS results are heavily influenced by atmospheric changes which are difficult to remove using the phase - elevation correlation alone, more work must be done before real signal can be differentiated from artifacts of the atmosphere removal process. It is this fact which motivates the second part of this study: an investigation of the effects of atmosphere on StaMPS processing at Mount St Helens.
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-The altitude of each pressure level is estimated for each climate data point. Example profiles are shown in figure ##. The Digital Elevation Model (DEM) used is from the NASA’s Shuttle Radar Topography Mission (SRTM).
+**Figure 7.** Example MODIS profiles of Pressure, Temperature, Water Vapor Pressure, and Refractivity with respect to Altitude are shown. The refractivity is integrated from the DEM height to the top of the profile in the calculation of phase delay.
+The altitude of each pressure level is estimated for each climate data point. Example profiles are shown in figure 7. The Digital Elevation Model (DEM) used is from the NASA’s Shuttle Radar Topography Mission (SRTM).
 **Methods**

mark/main.txt · Last modified: 2014/12/10 13:05 by mdw12

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