\[ \def\d{d} \def\D{D} \def\p{p} \def\t{t} \def\w{w} \]
How to convert flow direction between different encodings in GRASS GIS
- 1 degree to 45degree
- 2 degree to power2
- 3 degree to taudem
- 4 degree to whitebox
- 5 45degree to degree
- 6 45degree to power2
- 7 45degree to taudem
- 8 45degree to whitebox
- 9 power2 to degree
- 10 power2 to 45degree
- 11 power2 to taudem
- 12 power2 to whitebox
- 13 taudem to degree
- 14 taudem to 45degree
- 15 taudem to power2
- 16 taudem to whitebox
- 17 whitebox to degree
- 18 whitebox to 45degree
- 19 whitebox to power2
- 20 whitebox to taudem
1 degree to 45degree
\begin{equation} \D=\d/45 \end{equation}
r.mapcalc ex="45degree=int(degree/45)"2 degree to power2
\begin{equation} \p=2^{8-\D/45} \end{equation}
r.mapcalc ex="power2=2^(8-degree/45)"3 degree to taudem
\begin{equation} \t=1+(\d/45\bmod 8) \end{equation}
r.mapcalc ex="taudem=1+(degree/45)%8"4 degree to whitebox
\begin{equation} \w=2^{(9-\D/45)\bmod 8} \end{equation}
r.mapcalc ex="whitebox=2^((9-degree/45)%8)"5 45degree to degree
\begin{equation} \d=45|\D| \end{equation}
r.mapcalc ex="degree=abs(45degree)*45"6 45degree to power2
\begin{equation} \p=2^{8-|\D|} \end{equation}
r.mapcalc ex="power2=2^(8-abs(45degree))"7 45degree to taudem
\begin{equation} \t=1+(|\D|\bmod 8) \end{equation}
r.mapcalc ex="taudem=1+abs(45degree)%8"8 45degree to whitebox
\begin{equation} \w=2^{(9-|\D|)\bmod 8} \end{equation}
r.mapcalc ex="whitebox=2^((9-abs(45degree))%8)"9 power2 to degree
\begin{equation} \d=45(8-\log_2{\p}) \end{equation}
r.mapcalc ex="degree=45*int(8-log(power2,2))"10 power2 to 45degree
\begin{equation} \D=8-\log_2{\p} \end{equation}
r.mapcalc ex="45degree=int(8-log(power2,2))"11 power2 to taudem
\begin{equation} \t=1+[(8-\log_2{\p})\bmod 8] \end{equation}
r.mapcalc ex="taudem=1+(8-int(log(power2,2)))%8"12 power2 to whitebox
\begin{equation} \w=2^{(1+\log_2{\p})\bmod 8} \end{equation}
r.mapcalc ex="whitebox=int(2^((1+log(power2,2))%8))"13 taudem to degree
\begin{equation} \d= 45\times\begin{cases} \t-1&\text{if }\t-1>0\\ 8&\text{otherwise} \end{cases} \end{equation}
r.mapcalc ex="degree=45*if(taudem-1,taudem-1,8)"14 taudem to 45degree
\begin{equation} \D= \begin{cases} \t-1&\text{if }\t-1>0\\ 8&\text{otherwise} \end{cases} \end{equation}
r.mapcalc ex="45degree=if(taudem-1,taudem-1,8)"15 taudem to power2
\begin{equation} \p=2^{(9-\t)\bmod 8} \end{equation}
r.mapcalc ex="power2=2^((9-taudem)%8)"16 taudem to whitebox
\begin{equation} \w=2^{(10-\t)\bmod 8} \end{equation}
r.mapcalc ex="whitebox=2^((10-taudem)%8)"17 whitebox to degree
\begin{equation} \d= 45\times\begin{cases} 9-\log_2{\w}&\text{if }\w>1\\ 1&\text{otherwise} \end{cases} \end{equation}
r.mapcalc ex="degree=45*if(whitebox>1,9-log(whitebox,2),1)"18 whitebox to 45degree
\begin{equation} \D=\begin{cases} 9-\log_2{\w}&\text{if }\w>1\\ 1&\text{otherwise} \end{cases} \end{equation}
r.mapcalc ex="45degree=if(whitebox>1,9-log(whitebox,2),1)"19 whitebox to power2
\begin{equation} \p=2^{(\log_2{\w}+1)\bmod 8} \end{equation}
r.mapcalc ex="power2=2^((log(whitebox,2)+1)%8)"20 whitebox to taudem
\begin{equation} \t=\begin{cases} 8&\text{if }\w=4\\ (10-\log_2{\w})\bmod 8&\text{otherwise} \end{cases} \end{equation}
r.mapcalc ex="taudem=if(whitebox==4,8,(10-log(whitebox,2))%8)"