# Portable and Easily-Deployable Air-Launched GPR Scanner
## 5 Conclusions  
This contribution presented a portable measurement setup, conceived to enable extensive GPR measurements and devoted to testing the hardware that composes the payload of a UAV-based GPR system, as well as validating new algorithms to improve the quality of the resulting radar images. The implemented setup allows taking into account some of the uncertainties and factors that will be present in the airborne system, providing a validation and testing scenario closer to the one to be faced with a UAV.  
Three validation examples have been presented: in the first two, the same payload configuration as the one described in [14] has been considered, aiming to assess the feasibility of the measurement setup to conduct experiments in different scenarios (loamy and sandy soils). The third example focuses on testing log-periodic antennas that can operate at lower frequencies than Vivaldi antennas, but at the expense of a larger phase center displacement. To overcome this issue, a phase center compensation technique that takes advantage of the measurements that can be carried out with the setup has been implemented and validated.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Section** & \begin{tabular}{c} **Target** \\ **(size, cm)** \\ \end{tabular} & \
\begin{tabular}{c} **Depth** \\ **(cm)** \\ \end{tabular} & **Soil** &
\begin{tabular}{c} **GFR Antennas** \\ **(Working BW)** \\ \end{tabular} & **Reflectivity** \\ \hline
3.1 & \
\begin{tabular}{c} Mortar grenade \\ (30 \(\times\)8) \\ \end{tabular} & \(15\) &
\begin{tabular}{c} Loamy (\(\epsilon_{e}\in[50,7.0]\)), \\ moisture (\(\epsilon_{0}\),50\%)\({}^{*}\)\({}^{*}\)\({}^{*}\)\({}^{*  
**Author Contributions:** Conceptualization, Y.A.L., M.G.-F. and F.L.-H.A.; methodology, M.G.-F., D.C.M. and Y.A.L.; software, M.G.-F., D.C.M., G.A.-N. and Y.A.L.; validation, A.D.M., D.C.M., G.A.-N., M.G.-F. and Y.A.L.; resources, Y.A.L., F.L.-H.A. and M.G.-F.; data curation, M.G.-F. and Y.A.L.; writing--original draft preparation, Y.A.L., A.D.M. and D.C.M.; writing--review and editing, M.G.-F., G.A.-N. and F.L.-H.A.; supervision, F.L.-H.A. and Y.A.L.; project administration, F.L.-H.A. and Y.A.L.; funding acquisition, F.L.H and Y.A.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Ministerio de Educacion--Gobierno de Espana under Grant FPU15/06341 and FPU15/06431; by the Ministerio de Defensa--Gobierno de Espana and the University of Oviedo under Contract 2019/SP03390102/0000204/CN-19-002 (\"SAFEDRONE\"); by the Xunta de Galicia - Axencia Galega de Innovacion (GAIN) under project 2018-IN855A 2018/10 (\"RadioUAV: drones para aplicaciones mas alla de lo visible\"); by the Government of the Principality of Asturias (PCTI) and European Union (FEDER) under Grant IDI/2018/000191; and by the Instituto Universitario de Tecnologia Industrial de Asturias (IUTA) under Project SV-19-GJION-1-17 (\"RadioUAV\").  
**Acknowledgments:** The authors would like to acknowledge the CIED-COE (Col. [PERSON]) for the lease of the mortar grenade used in the tests, and Cap. [PERSON] for the supervision.  
**Conflicts of Interest:** The authors declare no conflict of interest.