# Generation of Persistent Scatterers in Non-Urban Areas: The Role of Microwave Scattering Parameters

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Method

_{E}, y

_{N}} and SAR {x, y} coordinates. Radar antennas in S1 and S2 points illuminate the ground surface, shown in gray, corresponding to the same pixel on the co-registered SAR images. The variables ϑ, R and ξ give, respectively, the mean radar look angle, the range distance between the spaceborne SAR interferometer and the ground and the satellite track angle. This is modelled as a rough planar surface

_{1}and E

_{2}as

_{12}and M

_{11}(M

_{22}) are the Hankel transforms, respectively, of the joint and self-characteristic functions of ε and ε’ [10]. Hence, the interferometric coherence is obtained as a function of terrain slope S and aspect A angles, by substituting the values of α and β derived from the following Equations (8) and (9) (see Appendix A for details) in (4)–(7)

## 3. Geological and Geomorphological Settings

^{2}. Figure 2 displays an orthophoto of the study area, characterized by sparse vegetation which facilitates the SAR interferometry analysis. Figure 3 shows the lithological maps of the study area. All LUs are summarized in Table 2. However, it is also possible to discriminate within a LU the relative weight of each lithological type. For instance, in the case of LU # 2 (limestones and marls) the order of lithological units means that limestones are more abundant than marls. Hence, LUs from # 1 to # 6 are all characterized by an overwhelming presence of limestones. This “hierarchy” has a great relevance when the mechanical properties of materials are taken into account or when interpreting phase stability properties of InSAR signals scattered by those materials. The elevation ranges from 440 m at Alqueidão (teschenite batholith intrusion, LU 21 as shown in Figure 3) and 0 m in the southeast sector of the study area (Tagus river alluvial plain, LU 25 as shown in Figure 3).

## 4. Results and Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

_{E}, y

_{N}} as

## References

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**Figure 1.**Geometrical configuration of InSAR data acquisition (see text for the definition of variables).

**Figure 5.**Normalized frequency distributions of LU units (

**a**), slope (

**b**) and aspect angles (

**c**); normalized frequency distributions of PS (ERS 1992–1997) as a function of lithological units (

**d**) slope (

**e**) and aspect classes (

**f**).

**Figure 6.**Frequency distribution of PS (1992–1997) as a function of slope and aspect classes (

**a**), slope class and lithology (

**b**), and aspect class and lithology (

**c**).

Sensor | N. of Images | Time Interval | Look Angle | Orbit |
---|---|---|---|---|

ERS-1/2 | 29 | 1992–1997 | 23° | Descending |

ENVISAT | 14 | 2003–2005 | 23° | Descending |

Lithological Unit ID | Lithology | Lithological Unit ID | Lithology |
---|---|---|---|

1 | Limestones | 14 | Sandstones, mudstones, limestones and dolomites |

2 | Limestones and marls | 15 | Sand |

3 | Limestones and sandstones | 16 | Clays |

4 | Limestones, marls and sandstones | 17 | Volcanic complex of Lisbon |

5 | Limestones, sandstones and mudstones | 18 | Basalt |

6 | Limestones, marls, sandstones and mudstones | 19 | Basalt breccia |

7 | Marls and mudstones | 20 | Dolerite |

8 | Conglomerate | 21 | Techenite |

9 | Conglomerates, sandstones and mudstones | 22 | Riolite |

10 | Conglomerates, sandstones and claystones | 23 | Traquite and traqui-basalt |

11 | Sandstones | 24 | Weathered or not defined rocks |

12 | Sandstones and mudstones | 25 | Alluvium, terrace deposits and anthropogenic terraces |

13 | Sandstones, mudstones and dolomites |

Time Series | NTOT of PS | Man-Made Structures | Bare Soil |
---|---|---|---|

1992–1997 (ERS) | 4756 (100%) | 2027 (43%) | 2729 (57%) |

2003–2005 (ENVISAT) | 8003 (100%) | 2734 (34%) | 5269 (66%) |

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**MDPI and ACS Style**

Nico, G.; Oliveira, S.C.; Catalão, J.; Zêzere, J.L.
Generation of Persistent Scatterers in Non-Urban Areas: The Role of Microwave Scattering Parameters. *Geosciences* **2018**, *8*, 269.
https://doi.org/10.3390/geosciences8070269

**AMA Style**

Nico G, Oliveira SC, Catalão J, Zêzere JL.
Generation of Persistent Scatterers in Non-Urban Areas: The Role of Microwave Scattering Parameters. *Geosciences*. 2018; 8(7):269.
https://doi.org/10.3390/geosciences8070269

**Chicago/Turabian Style**

Nico, Giovanni, Sérgio C. Oliveira, Joao Catalão, and José Luis Zêzere.
2018. "Generation of Persistent Scatterers in Non-Urban Areas: The Role of Microwave Scattering Parameters" *Geosciences* 8, no. 7: 269.
https://doi.org/10.3390/geosciences8070269