Week1 - Intro

Definition of GIS: software and data that enables to answer questions involving location and spatial info. Yelp, G maps, etc. all count
Desktop GIS - editting, processing,
Web GIS - mostly for displaying

Vector and feature data
- categorical and multivariate data
  - e.g. each watershed has an attribute table
- Points, lines, polygons
  - Lines: 1D, can have an attribute record
  - Polygons: 2D, can have an attribute record
Raster data - continuous data
- grid of fixed-size pixels - uniform value within in pixel
- imagery (multiband raster data e.g. RGB) is raster data
map documents in ArcGIS
- stores representation of data, provide a workspace
- ext: .mxd
- the map data is not embeded.
Orthophoto: arieal photo after location corrected to the map
Watershed Analysis
- NHD – National Hydrography Dataset – A dataset that contains water bodies and streamlines for the United States
  - Flowlines – the streamlines contained within NHD
  - NHDPlus – an enhanced version of NHD that adds additional attributes for each streamline, such as contributing area, flow, elevation, WBD, etc. Often used in place of NHD.
- WBD – Watershed Boundary Dataset – a dataset containing nested watershed boundaries for the United States
  - HUCs – Hydrologic Unit Codes – the watersheds created by the WBD