CS 128/ES Lecture 6b1 Digital Map Sources I

CS 128/ES Lecture 6b2 The first rule of building a GIS Try to use somebody else’s data before you even think of generating your own

CS 128/ES Lecture 6b3 1. Geographic data portals

CS 128/ES Lecture 6b4 Nat. Geospatial Data Clearinghouse Composed of many federal agency reps. Developing the National Spatial Data Infra- structure Working with Office of Homeland Security

CS 128/ES Lecture 6b5 USGS: National Mapping Info. Primary responsibility for US mapping Mapping standards and metadata Topographic maps GNIS

CS 128/ES Lecture 6b6 US Bureau of the Census Address and population data, tied to the census tract TIGER maps

CS 128/ES Lecture 6b7 NYS GIS Clearinghouse Familiar site? Statewide aerial photographs DOT maps Gateway to many USGS & NYS products

CS 128/ES Lecture 6b8 University sites Prominent GIS programs: Cornell U. U. Buffalo U. Calif., Santa Barbara U. Minnesota

CS 128/ES Lecture 6b9 Commercial sites ESRI’s site (nice move, licensing GIS.com!) The GIS portal! ~ 100 GIS links GIS World

CS 128/ES Lecture 6b10 2. Geographic exchange formats De facto standard: a.k.a. “industry standard” based on market success of a particular software standard (ex. ArcView shapefile) De jure standard: developed by professional organization, such as ANSI or ISO (ex. SDTS in US) Regulatory standard: enforced by government (ex. cadastre maps for property/tax purposes)

CS 128/ES Lecture 6b11 Value of digital exchange standards

CS 128/ES Lecture 6b12 Examples of national standards SDTS (US): Spatial Data Transfer Standard (now mandatory for all federal agencies) CGIS (Canada): Canadian Geomatics Interchange Standard NTS (UK): National Transfer Standard

CS 128/ES Lecture 6b13 3. Raster data formats

CS 128/ES Lecture 6b14 Remote sensing data sets  NASA’s EOS program  France’s SPOT

CS 128/ES Lecture 6b15 EOS 19 Feb news item: Lack of Snow Drives Iditarod North

CS 128/ES Lecture 6b16 Digital Raster graphs (DRGs)  Scanned topographic maps at various scales  Resolution: 400 dpi typical  Projection and coordinate system: varies (read the metadata!)  Accuracy: roughly that of paper source maps  Layers: either 1 or 2. No full GIS capability

CS 128/ES Lecture 6b17 Sources of DRGs Commercial sources (e.g., Delorme, Silva)  1:24,000 or 1:100,000  ~ $100/state  various tools, but one layer

CS 128/ES Lecture 6b18 3-D renderings

CS 128/ES Lecture 6b19 USGS DRGs  1:24,000 or 1:100,000  two layers - features - topography  feature classes can’t be separated

CS 128/ES Lecture 6b20 DRG – viewing both layers The contour layer covers the features layer! What to do???