"यो देवस्सवितास्माकं धियो धर्मादिगोचराः ।
This sloka is not an unknown one. Moreover it is very well known as a part of the Sandhyavandanam routine.
But it is being taken as Dhyanasloka to be used in the aarambha and avasaana of the Gayatri Japa part of the Sandhyavandanam routine.
In fact, it is the sloka version in loukika samskrita for the Gayatri mantra which is in Vaidika samskrita.
It is a verbatim translation of the Gayatri Mantra.
This is word to word. Only 'धर्मादिगोचराः' is the explanatory extension added to 'धियः' . Rest all are word to word for the words of the Gayatri Mantra.
This sloka follows the SaayaNaachaarya's approach of taking the Gayatri Mantra as a single sentence with a relative clause (यत्तदर्थक) structure (In fact the sloka adds the words यत् and तत् for this purpose). Even the word धर्मादिगोचराः is in a close following of SaayaNaachaarya's bhaashya of the Gayatri Mantra.
Some of the words are the same as in the Gayatri Mantra. Those are यः , धियः, भर्गः, वरेण्यं .
Some others are replaced by equivalents/synonyms. Those are नः--> अस्माकं ,प्रचोदयात् ---> प्रेरयेत् , धीमहि ---> उपास्महे.
The remaining words( except 'धर्मादिगोचराः' which is the explanatory extension added to 'धियः' ) are the same as in the Mantra but in a different grammatical form. Those are देवस्य ---> देवः ,
सवितुः---> सविता ,तत् ---->तस्य.
Two additional words यत् and तत् are brought in to highlight the relative clause (यत्तदर्थक) structure.
Those who can not/ do not want to use the Mantra version of the Gayatri Mantra can freely use the sloka version as a substitute.
This fact that this is a sloka form substitute of the Gayatri Mantra desrves greater publicity
really धन्योस्मि .