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Digital Map Sources I. The first rule of building a GIS. Try to use somebody else’s data before you even think of generating your own. 1. Geographic data portals. Nat. Geospatial Data Clearinghouse. Composed of many federal agency reps. Developing the National Spatial Data Infra-structure - PowerPoint PPT Presentation
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CS 128/ES 228 - Lecture 6b 1
Digital Map Sources I
CS 128/ES 228 - Lecture 6b 2
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 228 - Lecture 6b 3
1. Geographic data portals
CS 128/ES 228 - Lecture 6b 4
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 228 - Lecture 6b 5
USGS: National Mapping Info.
Primary responsibility for US mapping
Mapping standards and metadata
Topographic maps
GNIS
CS 128/ES 228 - Lecture 6b 6
US Bureau of the Census
Address and population data, tied to the census tract
TIGER maps
CS 128/ES 228 - Lecture 6b 7
NYS GIS Clearinghouse
Familiar site?
Statewide aerial photographs
DOT maps
Gateway to many USGS & NYS products
CS 128/ES 228 - Lecture 6b 8
University sites
Prominent GIS programs:
Cornell U.
U. Buffalo
U. Calif., SantaBarbara
U. Minnesota
CS 128/ES 228 - Lecture 6b 9
Commercial sites
ESRI’s site (nice move, licensing GIS.com!)
The GIS portal!~ 100 GIS links
GIS World
CS 128/ES 228 - Lecture 6b 10
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 228 - Lecture 6b 11
Value of digital exchange standards
CS 128/ES 228 - Lecture 6b 12
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 228 - Lecture 6b 13
3. Raster data formats
CS 128/ES 228 - Lecture 6b 14
Remote sensing data sets
NASA’s EOS program
France’s SPOT
http://earthobservatory.nasa.gov
CS 128/ES 228 - Lecture 6b 15
EOS 19 Feb news item:
Lack of Snow Drives Iditarod
North
CS 128/ES 228 - Lecture 6b 16
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 228 - Lecture 6b 17
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 228 - Lecture 6b 18
3-D renderings
CS 128/ES 228 - Lecture 6b 19
USGS DRGs
1:24,000 or 1:100,000
two layers - features - topography
feature classes can’t be separated
CS 128/ES 228 - Lecture 6b 20
DRG – viewing both layers
The contour layer covers the features layer!
What to do???