Energy conservation in resource constrained wireless sensor networks (WSNs) is an important concern. Techniques such as, energy conserving MAC protocols have been proved to be efficient to minimize the energy consumption in such networks. However, techniques based on in-network data compression have dominated recent research works for reducing the network traffic thereby improving the network lifetime. A large number of compression techniques have been proposed in recent years with diverse applications in WSNs. This work presents a comprehensive analysis of various existing in-network data processing techniques based on compressed sensing in WSNs. The essential features, requirements and characteristics of compression algorithms in WSNs, are discussed in detail with a classification of existing algorithms into different categories. A set of parameters are identified for a comparative evaluation of these algorithms to determine the efficacy of such in-network data processing techniques in an environment such as a WSN.