# update on Scott's article

fig. 7 - wouldn't this be better with opposite colour scale (i.e. darker should be lower values)

line 100: change from "interferograms at 0.001° resolution" to "interferograms at 0.001° resolution in WGS-84 coordinate system"

## Table 1:

### Coherence
A measure of stability of the scattering surface through time.
- Multiple potential sources of coherence change including vegetation,
snow, water, ground deformation. Therefore, interpretations should
consider these interacting sources and their change through time.
- The magnitude of coherence change is a function of time depending
on the source of change.
- Dependent on relationship between slope and satellite geometry so
consideration of topography is required during interpretation.
- Varies markedly with SAR wavelength such that changes in
coherence are sensor specific.

### Wrapped interferogram
Ambiguous measure of apparent surface deformation in cycles of phase (fringes).
- Observed signal could be ~~dominated by topographic or other~~ **affected by** atmospheric effects ~~such as~~ from the **troposphere and** ionosphere and be misinterpreted as a deformation signal. **Corrections using a variety of methods including weather models and GPS stations can remove the atmospheric effects; however, these techniques may not work or increase errors where the atmosphere is highly variable, for example over steep and high relief topography.**
- Observed signal is relative to the satellite along a single look
direction, without known 3D components. Therefore, determining
the direction of the deformation is non-intuitive and non-unique.
- Interferograms may contain ~~seasonal~~ **other** signals (e.g. related to
vegetation), which are overprinted on any observed deformation
signal.
- **Filtering methods influence the observed signal and
therefore user interpretation.**

### Unwrapped interferogram
Cumulative measure of apparent surface deformation in the satellite line of sight.
- **Dependent on quality of wrapped interferogram and coherence**
- **Unwrapping errors cause steps dependent on SAR wavelength that influence user interpretation**
- ~~Observed signal could be dominated by topographic or other
atmospheric effects such as from the ionosphere and be
misinterpreted as a deformation signal.~~
- ~~Observed signal is relative to the satellite along a single look
direction, without known 3D components. Therefore, determining
the direction of the deformation is non-intuitive and non-unique.~~
- ~~Filtering and unwrapping methods influence the observed signal and
therefore user interpretation.~~
- ~~Interferograms may contain seasonal signals (e.g. related to
vegetation), which are overprinted on any observed deformation
signal.~~

### Time series
Temporal deformation change derived from a network of interferograms.
- **Reliability of time series depend on method, quality of interferograms and their network.**
- Measurements are relative to a reference area, which is assumed to
contain no deformation (unless tied to another data source such as
GNSS).
- Long term biases may be present over some land covers in particular
those containing vegetation (phase bias), which may be
misinterpreted as a deformation signal.
- **Other non-considered signal sources or errors in their estimation may degrade quality of the time series, for example effect of topography is sensor specific and neglected by some tools.**
- ~~Time series may contain seasonal trends (e.g. related to vegetation or
atmospheric contribution), which are overprinted on any observed
deformation signal.~~
- ~~The atmosphere (water vapour) can introduce errors in the
timeseries. Corrections using a variety of methods including weather
models and GPS stations can remove the atmospheric effects;
however, these techniques may not work or increase errors where the
atmosphere is highly variable, for example over steep and high relief
topography.~~