1 | $NO.pk$ | This is the number of peaks. | $M$ |

2 | $P-f$ | This is the amplitude of the first echo peak. | ${A}_{1}$ |

3 | $P-s$ | This is the amplitude of the second echo peak. When only two echo signals are detected, this parameter is 0. | ${A}_{2}$ |

4 | $P-l$ | This is the amplitude of the last echo peak. When only one echo signal is detected, this parameter is 0. | ${A}_{M}$ |

5 | $T-f$ | This is the time of the first echo peak. | ${T}_{1}$ |

6 | $T-s$ | This is the time of the second echo peak. When only two echo signals are detected, this parameter is 0. | ${T}_{2}$ |

7 | $T-l$ | This is the time of the last echo peak. When only one echo signal is detected, this parameter is 0. | ${T}_{M}$ |

8 | FWHM | This is the full-width at half-maximum of the first echo. | $2{\omega}_{1}\sqrt{2\mathrm{l}\mathrm{n}2}$ |

9 | $Va$ | This is the variance of the first echo. | $E[\{g({x}_{1}|\theta )-E[g({x}_{1}|\theta )]{\}}^{2}]$ |

10 | $E-f$ | This is the energy of the first echo. | $E\left[\{g{({x}_{1}|\theta )}^{2}\right]$ |

11 | $E-l$ | This is the energy of the last echo. When only one echo signal is detected, this parameter is 0. | $E\left[\{g{({x}_{M}|\theta )}^{2}\right]$ |

12 | $Ku-f$ | This is the kurtosis of the first echo. | $\frac{1}{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}1}-{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}1}}\sum \left[{\left(\frac{(y(x|\mathrm{p}\mathrm{a}\mathrm{r}{\mathrm{t}}_{1})-{\mu}_{1})}{{\sigma}_{1}}\right)}^{4}\right]$ |

13 | $Ku-l$ | This is the kurtosis of the last echo. When only one echo signal is detected, this parameter is 0. | $\frac{1}{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}M}-{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}M}}\sum \left[{\left(\frac{y(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{M})-{\mu}_{M}}{{\sigma}_{M}}\right)}^{4}\right]$ |

14 | $RM$ | This is the root mean square of the first echo. | $\sqrt{\sum \frac{g{({x}_{1}|\theta )}^{2}}{{n}_{1}}}$ |

15 | $F-f$ | This is the form factor of the first echo. | $\frac{E\left[\{g{({x}_{1}|\theta )}^{2}\right]}{E\left[{\{g({x}_{1}|\theta )-E\left[g({x}_{1}|\theta )\right]\}}^{2}\right]}$ |

16 | $F-l$ | This is the form factor of the last echo. | $\frac{E\left[\{g{({x}_{M}|\theta )}^{2}\right]}{E\left[{\{g({x}_{M}|\theta )-E[g({x}_{M}|\theta )]\}}^{2}\right]}$ |

17 | $Pf$ | This is the crest factor of the first echo. | $\frac{{A}_{1}}{E\left[\{g{({x}_{1}|\theta )}^{2}\right]}$ |

18 | $I$ | This is the impulse factor of the first echo. | $\frac{{A}_{1}}{E\left[{\{g({x}_{1}|\theta )-E\left[g({x}_{1}|\theta )\right]\}}^{2}\right]}$ |

19 | $M$ | This is the margin of the first echo. | $\frac{{A}_{1}}{{\left(\frac{1}{{n}_{1}}{{\sum}_{1}^{{n}_{1}}}_{\sqrt{|g({x}_{1}|\theta )|}}\right)}^{2}}$ |

20 | $Sk-f$ | This is the skewness of the first echo. | $\frac{1}{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}1}-{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}1}}\sum \phantom{\rule{negativethinmathspace}{0ex}}\left[{\left(\frac{y(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{1})-{\mu}_{1}}{{\sigma}_{1}}\right)}^{3}\right]$ |

21 | $Sk-l$ | This is the skewness of the last echo. | $\frac{1}{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}M}-{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}M}}\sum \left[{\left(\frac{y(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{M})-{\mu}_{M}}{{\sigma}_{M}}\right)}^{3}\right]$ |

22 | $\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}-f$ | This is the pulse area of the first echo. | $\int g({x}_{1}|\theta )\mathrm{d}x$ |

23 | $\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}-l$ | This is the pulse area of the last echo. | $\int g({x}_{M}|\theta )\mathrm{d}x$ |

24 | ${L}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}}$ | This is the left side of the first return waveform, which consists of all points that lie between the first element of the first-return signal and its maximum. | ${{\int}_{{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}1}}^{{T}_{1}}}_{\sqrt{1+{y}^{\mathrm{\prime}}{(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{1})}^{2}\mathrm{d}x}}$ |

25 | ${L}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}}$ | This is the right side of the first-return waveform, which consists of all points that lie between the first element of the first-return signal and its maximum. | ${{\int}_{{T}_{1}}^{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}1}}}_{\sqrt{1+{y}^{\mathrm{\prime}}{(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{1})}^{2}\mathrm{d}x}}$ |

26 | ${L}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}-\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}}$ | This is the deviation between ${L}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}}$ and ${L}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}.}$ | ${\int}_{{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}1}}^{{T}_{1}}\sqrt{1+{y}^{\mathrm{\prime}}{(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{1})}^{2}}\mathrm{d}x$$-{\int}_{{T}_{1}}^{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}1}}\sqrt{1+{y}^{\mathrm{\prime}}{(x|{\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}}_{1})}^{2}}\mathrm{d}x$ |

27 | ${A}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}}$ | This is the ratio of the width to the height of the left waveform of the first echo. | $\frac{{T}_{1}}{{T}_{1}-{T}_{\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{t}\mathrm{\_}1}}\phantom{\rule{thickmathspace}{0ex}}$ |

28 | ${A}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}}$ | This is the ratio of the width to the height of the right waveform of the first echo. | $\frac{{T}_{1}}{{T}_{\mathrm{r}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{\_}1}-{T}_{1}}$ |

29 | $Pr$ | This is the percentage of waveforms exceeding a certain amplitude threshold. | $\sum T(\mathrm{w}\mathrm{h}\mathrm{e}\mathrm{n}\phantom{\rule{thinmathspace}{0ex}}y(\theta )>\phantom{\rule{negativethinmathspace}{0ex}}1500)$ |

30 | $P-fl$ | This is the amplitude deviation of the first and last echo. | ${A}_{1}-{A}_{M}$ |

31 | $T-fl$ | This is the time interval between first and last echo. | ${T}_{1}-{T}_{M}$ |

32 | $PR-fl$ | This is the ratio of the amplitude of the first and last echo. | ${A}_{1}/{A}_{M}$ |

33 | $P-fs$ | This is the amplitude deviation of the first and second echo. When only two echo signals are detected, this parameter is 0. | ${A}_{1}-{A}_{2}$ |

34 | $T-fs$ | This is the time interval between first and second echo. When only two echo signals are detected, this parameter is 0. | ${T}_{1}-{T}_{2}$ |

35 | $PR-fs$ | This is the ratio of the amplitude of the first and second echo. When only two echo signals are detected, this parameter is 0. | ${A}_{1}/{A}_{2}$ |

36 | Nose | This is the mean value of environmental noise. | $\overline{N}$ |

37 | Nose-st | This is the standard deviation of environmental noise. | $E[{N}^{2}]$ |

38 | Length | This is the duration of the signal higher than ambient noise. | $T(|y(\theta )>(N+3\sigma )|)$ |