With the availability of meter resolution space-borne SAR systems, urban monitoring using SAR Tomography (TomoSAR) becomes increasingly popular, because of its layover separation capability. However, compared to Persistent Scatterer Interferometry (PSI), TomoSAR applications are much more computationally expensive. This article introduces a TomoSAR processing system for long-term large urban area mapping and monitoring. Two new features were introduced: 1. PSI was integrated into the currently available TomoSAR algorithms (e.g. TSVD, SVD-Wiener, and SL1MMER) to increase the overall computational efficiency; 2. results from multiple view angles were fused to provide full coverage of each building façade. This processing system handles an entire TerraSAR-X high resolution spotlight scene in an affordable time, achieving scatterer density up to 1 million scatterer/km2 from a single stack, comparing to 60 thousand to 100 thousand scatterer/km2 for PSI.