Products of a GIS: Maps and Other Information - Introducing Geographic Information Systems with ArcGIS - page 206

This is a rapidly growing area of endeavor. However, the software to do this will evolve rapidly so if you are
going to be occupied with Internet map publishing in a couple of years from now you might want to wait to
learn the details.
Exercise 3-7 (Major Project)
Enhancing Communication: Styles, Layer Files, Layer
Packages, Reports, Charts, and Graphics
Somewhere in the conceptual space between raw data and finished maps lie the ideas of styles, layer files, and
map templates. We've already looked at templates, which may or may not have data associated with them.
Layer Files
Layer files are based on raw data files. Basically, a layer file tells ArcMap how to draw a data file—what
symbols and colors to use. As you know, if you add a raw data file in ArcMap, the software makes random
choices as to how feature are drawn. Sometimes this is satisfactory; more often it is not, if you have
serious intentions of examining and analyzing the data. Let's look at an example, in which you can see an
obvious advantage to choosing how features are symbolized.
1. Use ArcCatalog to copy the shapefile KY_Streams_spf from
[___]IGIS-Arc\Kentucky_wide_data
to
___IGIS-Arc_ YourInitials \Map_Making.
2. Start ArcMap with a Blank Map. Add
___IGIS-Arc_ YourInitials \Map_Making\KY_Streams_spf.shp
to the map, using Data View
This is a fairly large dataset (about 60 megabytes) that contains information about the streams
of Kentucky, from the largest (Order 8) to the smallest (Order 1). When two streams of the same
order (e.g., Order 1) come together, they make a stream of the next highest order (i.e., Order
2). However, if two streams of different order come together (e.g., Order 6 and Order 5), the
output is just a stream of the higher order (i.e., Order 6). 13 Therefore, “stream order” cannot
be considered true ordinal data, in terms of stream size, volume, rate of flow, and so on, even
relative to those streams that flow into it. That is, the Order 5 stream mentioned previously
might have a greater flow volume than the Order 6 stream it converges with.
13 This is according to the Strahler method of stream order analysis. In another method, Shreve, headwater streams are
also assigned an order of 1. But when two or more streams converge, then the stream downstream of the confluence is
assigned an order equal to the sum of the orders of the upstream streams. Stream analysis is discussed in Chapter 8.