Why to use longde position in comparison to Thogal ?

Question from Wake
First Request Guru Ji: xsmission of intimate detail on how why to use longde (space) position and comparison to Thogal!!!
Longde is the series of space that correspond to the second statement of Garab Dorje, going beyound doubts. Normaly in the teaching once one has receive direct introduction on the Natural State and for example practice the 4 contemplation of Dzogchen Semde that help to reinforce what has been experience during the direct introduction. Then one might have some doubts about what is the natural, primordial state ? 
At this point it is recomended to practice Longde that is very precise and will help the practitioner to go beyound any doubts about what is his primordial state. 
Thogal,Trekcho, Yangti comes after with the thrid statement of Garab Dorje with the secret series that help to devllop and integrate all experiences remaining present in your natural condition or rigpa. 
For myself Longde was a very important step. Longde can be devellop for continuing to devellop the vision like in Thogal, it does not require any sun, light like in Thogal or a dark room with Yangti, any place is fine. However for a good practice of Longde it is better to have some experience with the inner yogas, like Yantra Yoga, Tsa lung thigle ..