[4][5] He, with Frits Agterberg, Qiuming Cheng, and Jennifer McKinley, led the monumental project on the Encyclopedia of Mathematical Geosciences to the completion.

From 1998 to 2001, he worked as a research scientist at the Centre for Remote Imaging Sensing and Processing (CRISP) of the National University of Singapore.

He was appointed Associate Professor of Faculty of Engineering and Technology, Multimedia University (MMU), Malaysia in 2001 and was also a Deputy Chairman of the Centre for Applied Electromagnetics (2003–07) there.

Sagar's research contributions span both basic and applied fields, and involves the fusion of computer simulations and modeling techniques in order to develop cogent models in discrete space to gain an understanding of dynamical behavior of complex terrestrial systems, such as water bodies, river networks, mountain objects, folds, dunes, landscapes, and rock porous media.

His work employs concepts stemmed out of recent theories—such as mathematical morphology, fractals, chaos, and morphometrics—to develop spatial algorithms for (i) pattern retrieval, (ii) pattern analysis, (iii) simulation and modeling, and (iv) reasoning and visualization of the spatial and temporal phenomena of terrestrial and GISci relevance.

One of such challenges is to understand the complexity in spatiotemporal behaviors of several terrestrial phenomena and processes via construction of process-specific attractors that may range from simple to strange.