Tutorial I - ArcInfo

ArcInfo

ArcInfo includes two modules; Arc and Grid. Arc is primarily used for file management and conversion applications, such as importing and exporting data, projecting data, and attributing data. Grid is used primarily for cell-based modeling (i.e. making hillshade, slope and aspect maps, and viewshed analyses using DEMs) and for viewing coverages and grids.

File Structures

When Arc is initiated, it defaults to the workspace directory, usually either C:\\Workspace or D:\\Workspace. All of ESRI's Arc products use a strict file structure called info files, which are part of the ArcInfo workspace directory system. Each coverage or grid that is created in Arc is assigned an info file in its respective workspace directory. Therefore, moving and copying files must be done using commands in Arc in order for the info files to be updated.

Importing DEMs

From a PC, navigate to the network workgroup computer, "slush." Click on "gis." Click on Nicaragua. Download the two DEMs (volcanconc27.dem and volcanmad27.dem) and the two transportation files (volcanconc_tr.e00 and volcanmad_tr.e00) to either C:\\Workspace or D:\\Workspace, whichever is the default workspace for your computer. Load ArcInfo. At the Arc Prompt, type:

demlattice volcanconc27.dem volcanconc

This will import the DEM into an Arc grid file. Repeat for the other DEM:

demlattice volcanmad27.dem volcanmad27

The files are now ready to be worked with in ESRI format (i.e. ArcInfo, ArcGIS, and ArcView).

Exporting Grids to DEMs

To export a grid to a ".dem" file, the command changes slightly:

latticedem volcanmad27 volcanmad27.dem

A DEM should be changed into a ".dem" file anytime you wish to transfer the data via CD or any other form of media.

Mosaicing DEMs

Now, splice together the two DEMs using the mosaic command. At the Arc prompt, type:

grid

At the grid prompt, type:

concepcion = mosaic(volcanmad, volcanconc)

The two DEMs have now been spliced into one, continuous DEM (named "concepcion").

Importing Coverages

At the Arc prompt, type:

import auto volcanconc_tr.e00 volcanconc_tr

and then:

import auto volcanmad_tr.e00 volcanmad_tr

we will merge these two transportation coverages later in ArcMap.

Creating Hillshade Maps

To create a shaded relief map, type the following commands:

If you are still at the Grid prompt, type:

q

At the Arc prompt, type:

hillshade concepcion concepcion_sh 320 50

The 320 refers to the position of the sun (320?) and the 50 refers to the sun aspect angle (50?).

ArcGIS

ArcGIS is composed of four key modules; ArcMap, ArcScene, ArcCatalog, and ArcToolBox. ArcMap is used to create traditional, two-dimensional maps. It is also the module that must be used to edit or alter coverages and shapefiles. ArcScene is ESRI's new three-dimensional mapping tool. DEMs, coverages, shapefiles, and images may be opened in ArcScene. ArcCatalog is the module used to copy and delete coverages, grids, and shapefiles. As discussed in the ArcInfo section above, Arc's unique file structure requires an "info" file. Thus, Arc files (coverages, grids, and shapefiles) cannot be simply transferred or renamed in windows explorer or other file management software. ArcCatalog is also the software used to write metadata for GIS data. Metadata is data that describes data (i.e. a text file that describes a DEM's projection, author, etc.). Finally, ArcToolBox is the module used to import and export data, re-project data, writing AML script programs, creating custom tools, and building data topology. Because ArcToolBox is a relatively simple tool, it will not be discussed in length here.