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.