How to format equation description?

Question

A small piece of code after equation

  \begin{tabbing}    
    where \= $fTTsc$:~  traveling time (office to site and back to office).\\
           \>$fTIsc$:~time to get safety instructions (this is specially true in \\
          \>\; industrial environment)\\
           \>$fSNETtsc$:~setting up survey network.\\                   
    \end{tabbing}

about code

How can I use tab or something else so that (line 1 traveling,line 2 time,line 3 setting)comes in one vertical line.

where   
     fTTsc:     traveling time (office to site and back to office).

     fTIsc:     time to get safety instructions (this is specially true in 
                industrial environment)

     fSNETtsc:  setting up survey network. 

I 'm breaking manually (which took a lot of time for 15 sentences) but how to do it automatically so that it looks perfect and nice.

time to get safety instructions (this is specially true in \\
          \>\; industrial environment)\\

Answer 1

Silently stolen from this answer (click).

\documentclass[preview,border=12pt,12pt]{standalone} % change it back to your own document class
%\documentclass[12pt]{article}
\usepackage{array,tabularx}

\newenvironment{conditions*}
  {\par\vspace{\abovedisplayskip}\noindent
   \tabularx{\columnwidth}{>{$}l<{$} @{${}={}$} >{\raggedright\arraybackslash}X}}
  {\endtabularx\par\vspace{\belowdisplayskip}}

\begin{document}

An equation just to start
\begin{equation}
        fTTsc+ fTIsc + fSNEtsc = 0
\end{equation}
where:
\begin{conditions*}
        fTTsc       &   traveling time (office to site and back to office)\\
        fTIsc       &   time to get safety instructions (this is specially true in industrial environment) \\
        fSNETtsc    &   setting up survey network
\end{conditions*}

\end{document}

Answer 2

Here are two ways to do — to be adjusted according to the real data, equations, &c.

        \documentclass[ a4paper]{article}

        \usepackage[utf8]{inputenc}
        \usepackage[T1]{fontenc}
        \usepackage{lmodern}
        \usepackage[showframe, nomarginpar]{geometry} 
        \usepackage{array, mathtools}

        \begin{document}
        \[ \text{Some more or less complex equation, } \]%
        where:  \begin{tabular}[t]{!{\vrule width0.8pt}>{$ }l<{$}@{\ }l@{}}
        fTTsc:  & traveling time (office to site and back to office).\\
         fTIsc:   &    \parbox[t]{0.5\textwidth}{time to get safety instructions (this is specially true in
                    industrial environment)}\\
         fSNETtsc: &   setting up survey network.
         \end{tabular}
         \vskip 2ex

         \begin{align*}
         \text{Some}  & \enspace \text{more or less complex equation} \\
           \text{where: } &\mathrlap{ \begin{alignedat}[t]{2}
         fTTsc: & \   & &  \text{traveling time (office to site and back to office) }\\
         fTIsc:   & &    &     \parbox[t]{0.42\textwidth}{time to get safety instructions (this is specially true in industrial environment)} \\
          fSNETtsc: & &    &   \text{setting up survey network.}
         \end{alignedat}}\\
         \text{Another} &\quad\text{somewhat more complex equation}
         \end{align*}

        \end{document}​

Answer 3

When I've faced this problem, I wrote a package eqexpl (since 14 Nov 2018 it is available on CTAN). With it you could add in preamble

\usepackage{eqexpl}
\eqexplSetIntro{where} % set parenthesis in the left of the first item
\eqexplSetDelim{:} % set delimiter to ":"

and then in document

\begin{eqexpl}
  \item{fTTsc}traveling time (office to site and back to office).
  \item{fTIsc}time to get safety instructions
    (this is specially true in industrial environment)
  \item{fSNETtsc}setting up survey network. 
\end{eqexpl}

The parenthesis could be set only in the left of the item, not above, in this case you could leave it default (none) and add the "where" before environment manually.