Midterm next Wednesday
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Transcript of Midterm next Wednesday
Midterm next Wednesday
Midterm• May start off with multiple choice
• Bulk will be short answer/short essay
• Lecture PPTs and your notes, readings in Longley et al., Zeiler
• Will not include – Labs or Arc Marine exercise
– Journal articles
Major concepts
• Representations• Object vs Field• Model, data model, analysis model• Data models
– UML terminology, basic procedure from• Reality --> conceptual --> logical --> physical
– Customized Arc GIS data models• For enterprise GIS
• Analysis Models– Binary, ranking, rating, weighted rating
Major concepts - cont.
• Geodatabase – what it is, why it’s important
• Topology, Spatial Analysis – what they are, why they are important, how they relate
• Object orientation– Identity, inheritance, encapsulation
• Data Sharing (barriers)
Concepts of Data SharingLongley et al., Chapter 11
NSDI ---> geodata.govGeospatial One-Stop
( GOS )• Who needs to share data?
– jurisdictions with common borders
– jurisdictions in a region
– private and public sectors
– local, state, and Federal agencies
– government and individuals
• Geospatial One-Stop– www.geodata.gov/
NSDI ---> geodata.govGeospatial One-Stop
( GOS )• State, local, private production of
geospatial data – loss of Federal monopoly, patchwork
– variable accuracy, level of detail
– the WWW
– everyone can be a producer, publisher, distributor ofgeospatial data
• See GEO 465/565 lecture #6– dusk.geo.orst.edu/gis/lec06.html#nsdi
Barriers to Data Sharing(1) interoperability
– will ArcGIS read Intergraph data?
– find a common format that both can read • output into the common format • input the common format
– is the common format the same as one of the GIS formats?
• if yes, only one conversion is needed • if no, two conversions are needed
– issues of format, syntax within ONE GIS
• Digital Line Graphs (DLGs)–vector topographic maps
–1:24,000, 1:100,000 ,1:10,000
Govt Agency Data Formats
• Digital Raster Graphics (DRGs)– raster topographic maps at
1:24,000
• Digital Elevation Models (DEMs)– raster elevation data
– 90m, 30m, 10m
– Oregon 10m DEMs from buccaneer.geo.orst.edu/dem
• Digital Orthophoto Quads (DOQs or DOQQs)– aerial photographs
– camera orientation, terrain info.
– raster images at 1m resolution
– 6m positional accuracy at scale of 1:12000
• Imagery– satellites
– Landsat, SPOT, SPIN, etc.
Govt Agency Data Formats
National Data Sharing (cont.)
• new high resolution commercial imagery • 1 m resolution• www.spaceimaging.com
Barriers to Data Sharing(2) how to describe what you need
– how to assess whether some data set fits the need?
Describing Data
• Metadata• Again, see GEO 465/565 lecture #6
– dusk.geo.orst.edu/gis/lec06.html#nsdi
• ArcCatalog– graphic thumbnail
– Tables
– FGDC format metadata
– ESRI format metadata
– XML format metadata
Issues with metadata?
• potential complexity– can be larger than the data set!
• investment to create– can be larger than the data set!
• carrots and sticks – FGDC’s "don't duck metadata"
Barriers to Data Sharing
(3) retrieval - large spatial data sets(4) national security - e.g., impact of 9/11(5) search engines
– how to know where to look on the WWW?– SAPs know where to look (more on this soon)
• National clearinghouse, www.geodata.gov/ or geographynetwork.com
• Regional and campus clearinghouses, • www.geo.oregonstate.edu/ucgis/datasoft.html• Google
Finding Data• How to find geospatial data on the WWW
– 10,000,000 servers worldwide and quickly rising
– containing order 1x 1015 bytes of information
– several servers contain more than 1 x 1012 bytes of geospatial information (terabytes)
• WWW search engines – Google, Yahoo, Ask Jeeves, Hot Bot, AltaVista
– send out “spiders” to find pages
– find the most important words in pages
– build a catalog of words
– how many pages contain the word "map”?
Finding Data (cont.)
• most important metadata element is geographic location – find me some data about area x
– only some areas have names • what if there's no name for the area you want?
– only some hits on a name lead to geospatial data
• search engines work on text, not GIS data sets
Some Searching Solutions
(1) Know where to look for a particular type of data – ortho.mit.edu contains a lot of DOQ data for
Massachusetts
– Valley library has free DOQ data for Oregon
– osulibrary.orst.edu/research/guides/maps/
maproom.htm
• USGS geospatial data is at the Eros Data Center, edc.usgs.gov
(1) Types of Data (cont.)
• Microsoft's Terraserver contains DOQs and Russian imagery– www.terraserver.microsoft.com
– >1 terabyte
– millions of hits per day
• EPA data, www.epa.gov– Corvallis ecoregion data at
www.epa.gov/wed/pages/ecoregions/
ecoregions.htm
• Again, only SAPs know this stuff ...
Some Searching Solutions (cont.)
(2) Go to a clearinghouse site • www.geodata.gov
– Over 300 servers
– Common metadata format, FGDC standard
– must select (multiple) servers to search
• Regional node of NSDI – Oregon Coastal Atlas, www.coastalatlas.net
Some Searching (cont.)
(2) Go to a clearinghouse site • many states have government-sponsored
clearinghouses – Oregon Geospatial Data Clearinghouse
– www.oregon.gov/DAS/EISPD/GEO/alphalist.shtml
• Campus clearinghouses– www.geo.oregonstate.edu/ucgis/datasoft.html
• ESRI-sponsored data sites – Geography Network, www.geographynetwork.com
Some Searching Solutions (cont.)
(3) Go to a digital library
a digital library whose contents are searchable by geographic location
• National Academy of Sciences report Distributed Geolibraries (1999)– using a map
– using a placename directory
– using coordinates
– what have you got about there?
Digital Libraries (cont.)
• specify area of interest as a box on a map • or one of millions of placenames• how do I know that the library is likely to
have what I want?– collection level metadata
– a description of the contents of a collection
Digital Libraries (cont.)
• OSU’s Oregon Explorer– oregonexplorer.info
• UCSB’s Alexandria Digital Library– www.alexandria.ucsb.edu
– Part of California Digital Library
– over 2,500,000 data sets
Some Searching Solutions (cont.)
(4) Issue-oriented site …
http://www.ushmm.org/googleearth/
Download and use Darfur KML from course lecture page
Who knows where Google will go with sites such as this?