German based TanDEM-X and TerraSAR-X satellites, launched in 2007 and 2010 respectively, begin their tandem orbit flight to create a new global DEM product of the Earth's surface to be available in 2014.
The TanDEM mission seeks to produce a global DEM at 12 meter sp
atial resolution with a relative vertical accuracy of less than two meters. With this kind of specification "'the TanDEM dataset will replace SRTM'". The US Shuttle Radar Topography Mission (SRTM) of 2000 is one of the best-known, near-global, space-borne DEM prior to TanDEM. Its best product has a 30 meter spatial resolution, and a vertical accuracy that varies from 16m to 10m.
Airborne laser instruments such as Lidar can achieve finer spatial resolution and vertical accuracy but their products are regional - they are not seamless maps of the whole Earth as TanDEM will be able to achieve. For more read the full story here.