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Intro to Geospatial Data
Jon Jablonski
February 26, 2002
For ASIS(&t) UW
Agenda
What’s it about?
• Entities
• Attributes •Urban
•City Hall
•4 per acre
•615 smoots
Maps ≠ GIS
• But in a way they are.– Same primitives– Also consist of layers– Answer some of the
same questions.
• GIS …– is dynamic– is a data structure– can be queried– can create new
information
both are cool.
What’s unique about spatial info?
• Ties an attribute to a location, without losing the ability to be structured, to be operated upon, to be transformed, and to be moved.
• Is a representation of 3d space onto 2 dimensions.– But people are working on leaping into 3d.
What are some attributes?
• Measurements are most common, and relate directly to research methods (570 anyone?)
Graphic: Geog 360, Nick Chrisman
Nominal
3941 Univ. Way10-H4545 Bldg3-I
Academic Computer Center13-G
Aerodynamics Lab12-OAerospace Research Bldg12-N
Allen Library10-M
Alumni House3-IAnderson Hall14-M
Architecture Hall11-K
Archives and Records11-G
Art Bldg6-N
Atmospheric Sciences-Geophysics 12-LBagley Hall12-L
Balmer Hall5-M
Benson Hall13-L
Ordinal
ARCview
• Views and themes.– Basic interface to data
• Tables– See the underlying structure.
• Layouts– Make pretty pictures.
Demo—what are you doing?
• Showing a layer with no context
• Adding a layer of stock data
• Adding some other unit to measure against
• Querying to restrict data set
Answer me a question.
• Show me the Indian population in central Washington, indicating whether or not people are living on a reservation.
Yakama Nation population.
Steps
• Display Washington counties.
• Select only central Washington– Invert selection– Delete
• Add reservation areas from earlier map
• Select by theme to isolate areas of interest
• Do the same for Census blocks.
Oh….
I don’t have the census blocks.
Finding data on the web
• Library
• GISdepot
• ESRI
• Census
• Etc etc etc etc
Places to find info
• https://wagda.lib.washington.edu/gis/uwonly/data/geolytics/wash/
• http://www.census.gov/population/www/socdemo/race.html
Select by intersection
• For finding part of one theme that intersect with another
• Can use as an attribute operation as well
Here’s a new problem
• Shapes aren’t quite the same.
• Data quality is a function of:– Who’s collecting it.– The scale upon which it is drawn.
How the heck to combine then?
• Query what’s in one to the other?
• Do it visually?
• How about 2 steps?– Join into tract table– Query for non-blank.
Other operations
• Buffers– Don’t kill my fish
• Distance networks – How far to the nearest bus stop.
• Scoring– Many planning decisions made by completely
made up formula• A true cynic would claim that formulas are made
up to get the desired answer.
More Manipulation
• Calculate– To build new fields when data doesn’t match– To create new information– To solve your silly equations
Buffers
Network operations
And: http://www.esri.com/library/userconf/proc95/to150/p113.html
Scoring
General ARChints
• File management is an issue. – Temp files get huge– Every layer has multiple files– Deleting a layer doesn’t delete it’s files– Operations make new files that may not be
destroyed automatically.