Discussion 1: How to discern measurement frameworks

Objectives of exercise:

1. Participate in a discussion session in section meeting
   Examples of maps and their underlying measurement framework
   Introduce data sources to be used in exercises
2. Each group (of size two or so) will be given on source to report on:
   Measurement scale (level)
   Reference systems (spatial, temporal, attribute)
   Measurement framework
   Representation

Purpose

The steps from measurement to representation involve a number of decisions that influence the potential use of geographic information. Data sources start with raw measurements, and place them in context so that they can be intrepreted as information. Specifically, all geographic information is placed in a temporal reference system, a spatial reference system, and an attribute reference system. But the reference system is not enough to determine what you can do with a source of information. The concept of a measurement framework encapsulates the selection of components that act as 'control' so that another component can be measured. Finally, information is represented in database and on a map using systems of symbols. In reading a map we need to peel back these layers to figure out what happened in the whole process.

In this exercise, you will find be assigned a source of geographic information. Prepare a 5 minute presentation (shared among your group) covering the:

1. level of measurement (and specific scale of measurement)
2. use of reference systems for time, space and attribute
3. measurement framework (using the typology in lecture and the text)
4. representation (how the measurements are transformed and presented)

Issues to consider

Methods of presenting geographic information have become somewhat ritualized through the influence of disciplinary training and bureaucratic traditions. Consider whether the product you describe was designed for a specific purpose or for a more nebulous 'general purpose' constellation of users.

Printed maps impose a number of constraints on the display of information. The size of the printing press, the colors available, the density of symbols all create a style of presentation that continues to influence the digital products. Many of these products started out as printed maps, so that approach still influences the digital database.

What to do

1. Four groups will be created and given their assignment first week.
2. Examine your material: (using ArcView and various source descriptions- metadata).
3. Prepare materials for presentation. Cover the following points:
   Measurement scale (and level)
   Reference systems used
   Measurement framework (what is controlled/measured? How?)
   Representation (How was the picture/database constructed? How do these steps alter the underlying information?)
4. Your group presents their results in discussion meeting 13/14 October (check schedule).

Students who do not participate in a group presentation will be required to cover the above material for a comparison of at least three. They will need to submit a four page comparison essay by 21/22 October. This is a lot more work.

Resources for this exercise

The Bainbridge Island data can be accessed by opening P:\geog460aut03\discussions\d01.mxd. Exercise 1 lab sessions will provide the mechanics for these operations. Each group will examine one of the source data layers. Groups are designated by NUMBER (related to the final form of the list below). Each group has TWO layers. Try to draw a comparison/contrast between your pair.

1. Land Cover classified from Landsat 1998 & Streets
2. Land Cover (vegetation) from airphotointerpretation 1971 & Forest Practices Act
3. Schools & Normalized Vegetation Difference Index (NDVI)
4. Soils (see Soil Manual online and specifically the K factor) & 10 meter DEM from USGS

Some Hints on how to discern a measurement framework

Echos from 360:

• Read the Legend
• Interpret the map
• Look for some metadata... (we give you some SKETCHY metadata above, not always available...)

But also, peel back the representation

• Was there a continuous measure that was classified just for presentation purposes?
• Ask yourself: how did the "lines" get on the map?
  • Are these objects imposed or the result of measurement?