Business

• Introducing the TAs and Technical Help Discussion List.
• Inquire about Site Visits
• Discuss lab protocol

Understanding Data

Spatially referenced data is maintained and made available by many organizations and people. It can be very useful for building models of places that we can use to explore and communicate. But, if we want to understand places using data, we first have to understand the data. This lecture will go through some of the fundamental aspects of GIS data, and how we can understand what it means and how we can collect it and use it.

The big Ideas

• Data record measurements and observations of entities and their attributes
• Metadata is data about the data, which is essential for understanding what the entities and attributes and referencing systems are recorded inthe data.
• Portrayals are the meaqns we use to combine data and display them in specific ways (e.g. in maps.)
• A Schema is a purposeful arrangement of data

A Funny Story

The Story of the Much Awaited Santa Monica GIS Data

Understanding Data in Context

See The GSD GIS Manual Page on Modeling Whats Important

Our First Problem: To Describe a Place and its Context

Introducing ArcGIS

ArcGIS is an example of a tool kit for visualizing and transforming spatially referenced data. There are other toolkits out there, most of them support all or some subset of the principals that we will discuss in this class. You can learn more about it from the following user-manuals:

• What_is_ArcGIS.pdf
• Using ArcMap .

I recommend that you download these manuals, especially 'Using ArcMap' to a folder on your computer for quick reference.

A tour of two GIS Datasets

In class we will take a look at two GIS Datasets related to Fields Point Rhode Island

Critical Demonstrations:

• How data record information about entities and their attributes
  • Vector-Relational datasets use rows and columns in tables
  • Image datasets use cells or pixels with values to record reflectance (photos and scanned maps)
  • Raster datasets also use cells and cell-values to record information about places
• Metadata comes in different forms.
• portrayals of data can reference a single dataset (layers) or multiple datasets (maps)
• Since portrayals contain references to datasets, a good dataset is designed to keep these relationships stable.
• A stable, purposeful arrangement of interrelated data is known as a schema.

Where Can we Find GIS Data and Metadata?

See The GIS Manual Page about Sources of GIS Data

• A Look at the GSD Data Collection and ESRI Maps and Data. See l:\public\geo
• A look at MassGIS
• A Look at Rhode Island GIS

  Introduce Coordinate Referencing Systems

  The Future of Geospatial Information Infrastructure

  Our tour of GIS data sources probably raises some questions in your mind:

  • Why isn't there one web service with all of the GIS data I would ever want?
  • What happens when we try to model phenomena that occur accross the boundaries of jusrisdictions?
  • Why are there different types of metadata in use (or why do some people use a standard form)
  • When will all of these data wrangling problems be solved?

  Our answer to this question will bring us to several sites:

  • The National Spatial Data Infrsatructure First, develop standards for metadata.
  • Open Geospatial Consortium Then develop standards for encoding data, and schema, and protocols for serving geospatial infomration on the web.
  • The National Map

  Essentially all of this boils down to gatting a lot of independent people and political units and independent agencies to agree to cooperate and to change the ways that they do things in order to serve a greater good. Amazingly enough, it is happening, but not surprisingly it is happening slowly.

  Similar and related efforts are being organized in other countries and multinational organizations. One of the biggest obstacles is very persistent and backward ideas concerning cost recovery and copyrights for use of government information.