LiDAR vs. SRTM: Resolution, Accuracy & Scale

LiDAR, or light detection and ranging, and SRTM, or the Shuttle Radar Topography Mission, are two different methods of wide-scale generation of DEMs, or digital elevation models.  SRTM is a NASA initiative, which aims to provide (relatively) accurate elevation data for (most of) the world, by remotely sensing via space shuttle.  LiDAR is a process of collecting surface data by aircraft, which involves radar, and provides a far more detailed- or high resolution- image than most other remote sensing methods.  Resolution, which we can derive from the size of the grid cells that compose a raster image, is an important consideration in choosing a DEM, as it can dictate the results of many terrain analyses one might perform using that elevation model.  

One terrain derivative one might require from a DEM is slope, a comparison of that which has been derived from the SRTM and the LiDAR data is shown above.  One can immediately recognize the lower resolution present in the SRTM image, and the higher degree of accuracy in the LiDAR data.  The scale one is working with could clearly influence the results of any spatial analyses performed, as is evidenced clearly from the above- the kind of generalization present in the SRTM data may be acceptable for very large, smaller scale projects, but obviously wouldn't be appropriate for anything requiring any kind of more localized detail.