The purpose of this paper is to present the methodology followed and the results obtained by the exploitation of UAS for rapid multi-temporal 3D mapping during the recovery phase of Russia's traditional settlement

Lesbos Island, Greece, which was highly damaged by the destructive earthquake magnitude 6.3 on 12 June 2017. By applying the above described methodology, it was possible to monitoring the recovery phase during July 2017 and

May 2020, which 302 from 340 buildings that had been severely damaged by the earthquake have been demolished. A small number of new buildings have also been rebuilt and a small number of buildings have just begun excavation of their construction.

The methodology of the present paper entails three steps, UAS data acquisition and 3D modeling on three different epochs, 19 May 2019, 29 September 2019 and 17 May 2020.

DSM difference and building volume calculation and evaluation of the results based on fieldwork and visualization of the change occurred during the post earthquake recovery phase. Structure for motion and multi-view stereo methods have been applied and produced, spatially accurate.

First, digital surface models. Second, 3D point clouds and 3 orthophoton maps of Russia. In parallel, GIS capabilities have been explored to calculate building volumes based on first DSM produced by UAS image processing.

Second, dam produced by 233 RTK measurements and third, building footprints derived by the digitization of the orthophoton map of 25 July 2017.

The cartographic visualization of the estimated volumes on the four dates aims to document the progress of the post earthquake recovery phase of the settlement of Russia.

Here you can clearly see the changes in the volumes of the buildings in the four different epochs with the three UAS flight campaigns.

The condition of various buildings during the three flight campaigns.

Buildings that did not present changes in time. This is a significant number of buildings in the settlement which either did not suffer any serious damage and suffered very light damages. Damage categories one and two according to the EMS 98 European code.

And consequently, these damages did not make it demolishable. It is worth noting that this category also includes several buildings which while they have suffered more serious damage,

however, their owners did not carry out restoration procedures through demolition. Buildings that were demolished. This is a critical number of buildings in the settlement which due to the seriousness of the damage suffered by the earthquake were demolished either until May 2019 or later.

Buildings that have been rebuilt. This is a limited number of buildings that have been rebuilt in the settlement. The following cases are distinguished. A. Buildings that were built in a very short period of time, one year, changing

not only the construction material but also the original design and area form of the building. B. Buildings that were built and retained the original plan and area. And C. Buildings that have just begun excavation for the construction.

The categories of buildings presented in the following charts created based on the volumes of the buildings for the periods between the three flight campaigns that took place in Vrisa, applying the described methodology.

The multi-temporal monitoring of the building's volume as calculated by the 3D mapping using UAS is an important indicator of monitoring the post-earthquake recovery phase of the traditional settlement. However, in order to better understand the changes in the mapping volumes it is necessary to

have a good knowledge of the areas that the buildings present in the specific settlement of Vrisa. More analytically, the traditional settlement of Vrisa consists mostly of small under 100 cubic meters to medium 100 to 150 cubic meters, single-story and two-story buildings with roofs.

The average floor height is about 3 meters, while the average height of the roof is 1.5 meters. In the volume chart between July 2017 and May 2019, the large number of demolition, 253 to 340, are found mainly of small

volume of buildings that constitute the majority of the buildings due to the traditional character of the settlement of the island of Lesvos.

The same diagram shows the early two buildings that were rebuilt shortly after the earthquake effect. The diagonal shows the buildings that were not damaged, while below the diagonal are the buildings that were demolished.

Above the diagonal are the two buildings were rebuilt. In the volume chart between May 2019 and September 2019, there is a reduced number of demolition of buildings that have been severely damaged by the earthquake and without the construction of the new buildings.

The small increase in the volume of a small number of buildings is due to the reconstruction of the roof, which was either severely damaged or collapsed. The roof is a basic feature of the buildings due to the traditional character of the settlement of the island of Lesvos.

In the diagram, it can be seen that the results are almost identical with the application of the above-described methodology with the results from the fieldwork. In the volume chart C between September 2019 and May 2020, we observe that demolition continues at a slow pace.

At the same time, the construction of buildings has begun, which have largely completed the static frame as well as the construction of roofs in buildings that had not been severely damaged.

This is damage category 3 according to EMS 98 European Code. This volume chart shows the nine new buildings that rebuilt, the small number of the reconstruction roofs, as well as the small number of buildings that were demolished.

Changes in volumes smaller than 100 cubic meters are due to the gradual removal of debris from the already destroyed buildings.

The evaluation of the results obtained from the application of the proposed methodology was carried out with fieldwork, which took place on the same date of the UAS image acquisition flights. In the present study, the methodology developed and applied for 3D mapping of the changes that took

place until May 17, 2020, achieves reliable results in the relatively easy, fast and economically feasible way.

By applying the above-described methodology, it was possible to monitor the recovery phase during July 2017 and May 2020, which 302 from 340 buildings that have been severely damaged by the earthquake have been demolished.

A small number of new buildings, 11, have also been rebuilt, and a small number of buildings, about five, that have just begun excavation for the reconstruction.

An important parameter of obtaining reliable data and comparable results is the proper selection of flight parameters, and they are maintained until epochs when the data collection is decided. The flight height, flight speed and front overlapping and the side overlapping are the most important parameters in the flights.

The above methodology proved that shooting video or images does not affect from creation of DSM, neither the calculation of the building's volume.