Meru Chakra Yantra is an important form of Goddess Shakti worship. This is used especially by Shakta worshippers.
When Goddess Shakti is in the Meru peak, the Avranas are piled up peak upon peak in a three-dimensional manner. It will be in the form of an upright cone. Such a three dimensional configuration of Sri Chakra is called ‘Meru Prastaram’. People call it just ‘Meru’ colloquially.
When the Chakra is two dimensional it is said to be ‘Bhu Prastaram.’
A mixture of the two (Meru Prastaram and Bhu Prastaram), where the beginning Avranas rise higher and higher, but later the latter Avranas are all in the same plane, is called ‘ardha meru’ (ardha means ‘semi’).
A Purna Meru is that which has all the Avaranas in the Meru-prastara style.
In Kanchi Kamakoti Mutt and in Thiruvidaimarudur Mukammal Temple, what you find is Purna Meru. In Mangadu, it is Ardha Meru. In the Kamakoshtam at Kanchipuram it is Bhu Prastaram