ZHANG, Ruda July 10, 2018:  Add manifold learning [ba3d5e6]
ZHANG, Ruda March 23, 2018:  More on WADGPS, map elements; topology/manifold, math branches, Taleb on probability [46880f6]
Ruda Zhang May 04, 2017:  Restructure econ notes [39e3490]
Ruda Zhang February 06, 2017:  GRASS GIS and its QGIS integration [eb3b14b]
Ruda Zhang January 19, 2017:  GpsPrune [0239a03]
Ruda Zhang January 03, 2017:  Geospatial data formats and standards. [507a2d2]
Ruda Zhang October 05, 2016:  GRASS GIS [772fc3c]
Ruda Zhang October 05, 2016:  Programming language support for GIS. [c16f2b5]
Ruda Zhang October 05, 2016:  correct format [58497b1]
Ruda Zhang September 25, 2016:  PCA is SVD; PROJ.4, JOSM, and geoprocessing [bc3a8ef]
Ruda Zhang September 01, 2016:  Add images to map projection methods. [5f4956c]
Ruda Zhang August 07, 2016:  Replace tab with two spaces. [adaa87b]
Ruda Zhang July 12, 2016:  GIS web services. [16d87f5]
Ruda Zhang July 05, 2016:  Add leaflet, QGIS; notes on decision trees. [9f2e957]
Ruda Zhang June 26, 2016:  one sentence per line [e15360a]
Ruda Zhang June 26, 2016:  add category tag to wiki pages [a9b356c]
Ruda Zhang June 26, 2016:  Use internal link for wiki pages. [22daaba]
Ruda Zhang June 26, 2016:  use canonical filename and no internal H1 [eeca8ff]