Atlas Help Topics

• Atlas Overview
• Introduction To The Atlas
  • A Definition Of Terms
  • Satellite Images (False-Color Infrared)
  • Digital Elevation Maps (with Rivers)
  • Sources for Atlas Images
• Navigating the Atlas
  • Outline maps, Graphic Index of Maps, and Detailed Color Maps
• Atlas Tools
  • Atlas Tools Window
  • Show/Hide Tools toggle
  • Plot Sites
  • Plot Sites in Area
  • Compute Distance
• Atlas Menu
  • Atlas Tools
  • Atlas Search
  • Map Search (By Site)
  • Map Search (By Region)
  • DEM Key
  • Clear Map
  • Plot Sites from Search Saver
  • Store Sites in Search Saver
• The Atlas and Memory Issues

Atlas Overview

The Perseus Atlas consists of:

• Black and White Outline maps in two scales
• Color Digital Elevation maps in three scales
• Color Satellite Image maps in 4 scales
• A Graphic Index of Maps
• An Atlas Tools window with nine functions
• An Atlas menu with five functions

With the various tools and functions you can:

• plot sites
• obtain geographical coordinates of sites
• plot sites in a selected area
• plot sites in a region
• calculate distances between a number of sites.

The Perseus Atlas is entered in the following way:

1. Click the Atlas icon on the Perseus Gateway or choose Atlas from the Links menu: the small Black and White Outline map (2600 mpp), and Atlas Tools window now appear. An Atlas option also appears on the menu bar at the top of the Outline map.
2. Click Graphic Index of Maps on the Atlas Tools window to go to the color map selection view. The Graphical Index of Maps (500 mpp) appears in a new window. The Index displays a black and white Outline map with highlighted rectangular sections. Click on a section to display a pop-up menu from which you can choose a Digital Elevation map or a Satellite Image map (where available).

The Perseus Atlas is an interactive tool for investigating the geography of the Greek world and the surrounding Mediterranean region. The Atlas has graphic drawings, digital elevation models, satellite images, and three-dimensional topography views. Various functions in the Atlas allow you to locate and plot sites, compute distances between sites, identify sites within a region, examine elevation and drainage, and zoom in and out to see maps of different scales. As a geographic reference, the Atlas can be used in traditional ways, but its content and design encourage more complex and interactive uses.

Here are some terms used to describe the Atlas. "Projection" refers to the system used to translate locations on a (nearly) spherical earth into the plane of a map. The large scale Black and White Outline map uses a Plate Carree projection. The other maps use the Universal Transverse Mercator (UTM) projection system.

"Coordinate system" refers to the system by which points on the current map are located. In Perseus, all geographic data are recorded in longitude and latitude coordinates, expressed in degrees (minutes, seconds) east of Greenwich, England and north of the Equator. The large scale lon-lat map works directly with these coordinates in a Plate Carree projection.

"Scale" refers to the meters-per-pixel ratio of the maps. Depending on the current map, the scale may be 1300, 1000, 500, 250, 125, or 60 meters per pixel. (A pixel is the unit of measure for a computer monitor.)

"Graphic Index of Maps" refers to the black and white line drawing of the Greek world overlaid with numerous rectangles. The rectangles are active areas that, when clicked, reveal a pop-up menu from which you may select a map of the desired theme (defined below). To move to an adjacent map to the north, south, east, or west, after you have selected a theme, click the directional arrows around the magnifying glass icon on the Atlas Tools window. To move to the next highest scale map in a theme, click on the plus sign inside the magnifying glass icon on the Atlas Tools window.To move to the next lowest scale map in a theme, click on the minus sign inside the magnifying glass icon. To return to the Black and White Outline map, click the Outline Map button on the Atlas Tools window.

"Theme" refers to the type of map selected, either the Black and White Outline maps or the color Digital Elevation maps and Satellite Image maps.

"Outline Maps" The Small (2600 meter per pixel) and Large (1300 meters per pixel) Outline maps enclose the coastline of the Greek world, from Sicily to Western Asia Minor, and from Campania to Crete, in a black and white line drawing. The site list has approximately 1,600 entries, which can be plotted on the outline map. The Small Outline map is the default selection when you open the Atlas. Plotting sites on it is a fast way to locate sites in their geographical context.

"Color Maps" are both the Digital Elevation maps and the Digitized Satellite images.

The satellite photography, shown as false-color infrared maps, covers the Greek mainland and is available in four scales: 500, 250, 125, and 60 meters per pixel. The maps show a standard coloration of three bands of satellite data using red, green, and blue. Bright red areas reflect heavy vegetation, and blue to gray areas indicate heavily urbanized areas.

The false-color infrared maps are based on five regions in mainland Greece:

1. Epirus (Albania/Illyria)
2. NW Greece (Acarnania, Phocis, Aetolia, etc.)
3. SE Greece (Attica, Boeotia, Euboea, Thessaly, etc.)
4. Peloponnese, including Attica
5. Macedonia/Thrace

Digital elevation maps with rivers: These maps have been created from digital information on land elevation. A range of colors, from yellow to dark brown, is used to describe elevation. These maps show streams and lakes overlaid on topography.

These color topography maps are based on 15 regions. The maps are digital elevation models that use color to indicate topography. The color topography maps are available in three scales, 500, 250 and 125 meters per pixel.

N. B. The key used to read elevations from the Digital elevation maps is brought up by choosing Show DEM Key from the Atlas menu. A small floating window with the color key and elevation scale appears. Hide the window by clicking the close button on the Key.

The color maps cover 15 regions of roughly 200 by 300 kilometers each:

• Campania
• Apulia
• Bruttium (Calabria)
• Sicily
• Epirus (Albania/Illyria)
• NW Greece (Acarnania, Phocis, Aetolia, etc.)
• SE Greece (Attica, Boeotia, Euboea, Thessaly, etc.)
• Peloponnese, including Attica
• Cyclades
• Macedonia/Thrace
• Marmara Sea
• Troad
• Ionia/Lydia
• Caria/Lycia
• Crete

The Atlas includes information from three kinds of sources: the Digital Chart of the World (DCW), the Landsat Multispectral Scanner (MSS), and printed materials of varying quality.

The DCW offers worldwide coverage of a variety of themes represented as vectors in the Vector Product Format. For the Perseus Atlas, the most important themes are topography and hydrography. The published accuracy of the DCW is roughly 1:1 million, but according to the developers of the DCW, the accuracy will be substantially better in many parts of the world.

The Landsat MSS sensors measure electromagnetic radiation at four different points in the spectrum: 0.5-0.6 micrometers (blue); 0.6-0.7 mm (green); 0.7-0.8 mm (low infrared); 0.8-1.1 mm (high infrared). Because different materials reflect and absorb radiation in characteristic ways, these data provide evidence of land cover.

The Atlas includes a database of approximately 1900 sites, based on maps published by the Greek Statistical Service, and on printed gazetteers. The Greek maps can be used reliably to within 30 seconds of longitude or latitude. (At 39 degrees of latitude, very near the center of our core area, 30 seconds of longitude represents about 720 meters on the ground.)

To navigate among the Atlas's many images and find the ones most useful to you, spend some time learning how the Atlas works.

In broad terms, the Atlas maps can be categorized in three ways: as Outline maps, a Graphic Index of Maps, and detailed Color maps (Digital Elevation and Satellite Image maps). The 2600 meter per pixel (MPP) Outline map of the Greek world is the entry point of the Atlas. It is accessed either by clicking the Atlas icon on the Perseus Gateway, or by choosing Atlas from the Links menu. To expand to 1300 meters per pixel (MPP), click the plus sign on the magnifing glass icon on the Atlas Tools window. The various features of the Atlas Tools window and the Atlas menu can be used with both Outline maps (described below).

N. B. The NEC Pentium computer with 16 Meg RAM takes about a minute and a half to bring up the 1300 mpp Outline map. To revert to the 2600 mpp Outline maps takes about 5 seconds.

The Graphic Index of Maps enables you to access the detailed Color maps; it is analogous to the map keys found in traditional print atlases. The Color maps come in up to four scales. You choose which sector of the Greek world and which scale you want from the Graphic Index of Maps (described in detail below).

Use of a print atlas map key is intuitive; you find the tile corresponding to the part of the world you want a detailed map of, and then turn to the atlas page indicated by the number in the corner. Similarly, each tile in the Perseus Graphic Index of Maps takes you to a detailed map, but instead of turning pages, you choose the desired item from a pop-up menu.

The following examples are arranged to show first how to display the various map themes, then how to use the specialized map tools.

Task: Enter the Perseus Atlas environment.

From the Gateway, click the Atlas icon. Or from anywhere in Perseus, choose Atlas from the Links menu. Your point of entry into the Atlas is the Small Outline map of the Greek world.

Notice that along with the map, a window appears, the Atlas Tools window, and that a new menu, Atlas, appears on the menu bar.

N. B. You may have to drag the Black and White map out of the way in order to get to the Atlas Tools window. Or you may fetch it by choosing Atlas Tools from the Atlas menu.

Task: Go to the Large Outline map of the Greek world.

Find the magnifying glass icon on the Atlas Tools window. Plus and minus signs are in the lens. To bring up the Large Outline map of the Greek world, click the plus sign on the magnifying glass icon. You can toggle from Small to Large Outline maps by clicking the plus and minus signs.

Task: Go to the Graphic Index of Maps.

From either the Small or Large Outline map of the Greek world, click the button Graphic Index of Maps on the Atlas Tools window. An outline map appears with active rectangles, or tiles, overlaid. The button on the Atlas Tools window now reads Outline Map; you can click it to return to the Outline maps. Move the mouse over the tiles, and note that they become highlighted.

Task: Go to the detailed maps.

Move the mouse to the tile over the Attic peninsula (middle row, third from left). Hold the mouse down to bring up a pop-up menu. To see a detailed map, choose one of the pop-up menu items. The items available are Digital Elevation map and Satellite Image map. In this example, choose Satellite Image map.

When you go to one of the Color maps, a new button appears on the Atlas Tools window, which toggles between the Digital Elevation Maps and the Satellite Image Maps. You can switch between Satellite Image maps and Digital Elevation maps by clicking this button. However, it is necessary to return to the Graphic Index of Maps to go to a Black and White Outline map. If you plotted any sites (see below) on the color map you chose, they will be preserved. After you close a map, any plotted sites will be lost unless you first save them by clicking the Search Saver icon on the Navigator window. To replot the sites, choose Plot Sites from Search Saver from the Atlas menu. To return to the Graphic Index of Maps, click the button Graphic Index of Maps the Atlas Tools window.

N. B. Some tiles do not have Satellite Image maps: namely, those over Sicily, Italy, northern Epirus, the Troad, Asia, the Cyclades and Crete.

The Atlas has unique tools for navigating among the themes, scales, and maps. The tool set includes the Atlas Tools window with its special features, the Atlas menu, which includes a browser called the Atlas Search and various customizing settings.

The Atlas Tools window is a window that that appears when you enter the Atlas. It provides controls to navigate the Atlas. It also gives information about the current map. Sites for the current map, their coordinates and distance computation between sites are reported in the Atlas Tools window (described below).

The scale bar shows the distance taken up by one hundred pixels of the monitor's screen. The distance represented by the scale is shown above it in kilometers and changes depending on the scale of the map.

The directional reference on the map is indicated by the arrow labeled "N" for north. This orientation is constant. An icon map of Greece to the right of the North arrow changes color to show the active map theme. To the icon's right and below it is the button which changes to go to either the Graphic Index of Maps or the Outline map.

The small magnifying glass surrounded by directional arrows is a navigation tool for moving among maps in the current theme. To change the scale of a map within a theme, click the plus sign (+) in the magnifying glass and you will zoom in to the next larger scale of the current map, if one is available. Click the minus sign (-) and you will zoom out to the next smaller scale of the current map, if one is available. Click the up, down, left or right arrows extending from the circumference of the magnifying glass to move to the adjacent map, if one is available.

The color maps come in four scales: 500 meters per pixel, 250 meters per pixel, 125 meters per pixel and 60 meters per pixel. A pixel is a dot on the monitor of your computer. Because monitors vary from workstation to workstation, the representation of a geographical distance will also vary. However, you can readily get a sense of distance in the Atlas from the kilometer scale on the Atlas Tools window; its length is always 100 pixels, and the equivalent of 100 pixels in kilometers is displayed above the scale for each map. Not every theme is available in each of the four scales. Satellite images are the only theme coming in the 60 meter/pixel resolution. The pop-up menu for each tile of the Graphic Index of Maps displays the themes available.

The Show Tools/Hide Tools toggle switch alternately shows and hides three additional map tools, Plot Sites, Plot Sites in Area and Compute Distances (see below). When the map tools are showing, they are attached to the lower part of the Atlas Tools window.

The following exercises will help you to navigate through the Atlas.

Task: See the four map scales available from the Graphic Index of Maps.

Enter the Graphic Index of Maps by clicking the button on the Atlas Tools window. There will be 15 tiles imposed upon regions covered by the color maps. By default the scale displayed is the smallest, 500 meters per pixel, as is shown on the title bar. (The figure 260 km which you see currently displayed on the Atlas Tools window is the scale for the entire outline map.)

Increase the scale by clicking the plus sign of the magnifying glass icon on the Atlas Tools window once. There will now be 56 tiles imposed upon regions covered by detailed maps. Each tile represents a detailed map at a scale of 250 meters per pixel. Note that each of the former tiles is now subdivided into four tiles, with the exception of the tile over the upper Bosphoros (250 meter/pixel resolution is not available for that region). Increase the scale to 125, then 60 meters per pixel by clicking on the plus sign of the magnifying glass icon. Note that the number of tiles on the Graphic Index of Maps again increases by a factor of four. You can decrease the scale back to 125, 250 and 500 meters/pixel by clicking on the minus sign on the magnifying glass.

Task: See detailed maps in the four available scales.

This example will use the Satellite image theme and zoom in on the Isthmus of Corinth.

From the Graphic Index of Maps at 500 meters/pixel scale, move the mouse to the tile over the Corinthiad (second row from top, third tile from left). Choose Satellite Image from the pop-up menu. The satellite image will appear. The Isthmus of Corinth is the neck of land in the lower left quadrant connecting the Attic peninsula above with the Peloponnesus below.

To zoom in to the 250 meters/pixel scale, click the + sign on the magnifying glass icon on the Atlas Tools window. Now move the cursor over the Isthmus of Corinth and double-click it. The 250 meter/pixel satellite image will appear, with the Isthmus of Corinth in the lower right quadrant.

Zoom in to 125 meters/pixel by clicking the Isthmus; click the Isthmus again to reach the 60 meters/pixel map. You can decrease the scale by clicking on the minus sign in the magnifying glass on the Atlas Tools window.

Task: Use the directional arrows on the Atlas Tools window to go to adjacent maps in the same theme.

Four arrows at 90 degree intervals surround the magnifying glass. These directional arrows, when clicked, move you to an adjacent map in the current scale (north, south, east, and west, respectively, for up, down, right, left). By using the directional arrows, you can skip the step of returning to the index to see an adjacent map.

For the following examples, use the Small Outline Map of the Greek World. If you are already inside the Atlas, click the button Graphic Index of Maps on the Atlas Tools window, then click the button Outline Map. Else, from the Gateway, click the Atlas icon; from anywhere in Perseus, choose Atlas from the Links menu.

Task: Use the Plot Sites and Compute Distances features.

Click the Show Tools toggle on the Atlas Tools window. The window will expand to reveal two display fields, two round buttons, three square buttons and a square switch.

N. B. You cannot operate the Show Tools toggle from the Graphic Index of Maps.

Maps in Perseus appear without political boundaries or other editorial indications of human settlement. The Plot Sites tool allows you to plot sites on a map by selecting sites from the scrolling field Select Sites, lower left. The Site in Region list in the expanded Atlas Tools window shows in alphabetical order the sites that can be plotted on the current map. The list of sites ranges from more than 2,000 sites that can be plotted on the large scale Outline map to 2 or 3 sites on some color maps of sparsely populated areas.

Task: Plot the site of Delphi on the Outline map.

Make sure that one of the Outline maps is the active window, and that the Atlas Tools window is toggled to Show Tools. The Sites in Region list will indicate that 1626 sites in the Greek world can be plotted. Scroll down the Sites in Region list and double-click Delphi. Delphi will appear on the map, and in addition, the latitude and longitude will be displayed in the upper field of the Atlas Tools window. The Plot Sites feature works in the same way with the color maps, except the number of sites in each map shown in the Sites in Region list will vary.

The scroll bar at the right side of the Sites in Region list provides a quick way to move through the list. (Remember that you can drag the scroll indicator up or down to move quickly in a list, rather than moving line by line.)

The site you plot is marked with a dot; the site name may be dragged to another location on the map. You may need to drag the Atlas Tools window out of the way in order to see the plotted sites.

N. B. If you double-click a site, Perseus will form a link with the Lookup tool.

If you want to plot a number of sites:

• to select a continuous range of sites, click-drag the mouse down the list, then click the button Plot Sites.
• to select a discontinuous range of sites, control-click the mouse at various sites on the list, then click the button Plot Sites. The last site plotted appears in the Lat-Lon field.
• to plot all sites possible on a map, click the button Plot All Sites. (Perseus can plot all 1626 sites on the Outline map, but it will take almost half a minute.)
• to clear the map, click the button Clear Map.

N. B. You can switch off the labels designating the sites by clicking the square button Show Site Labels. This could be useful for having students identify sites in a quiz.

This feature plots all known sites within a rectangular region that you define by selecting it on the map.

Task: Define an area in Thrace for the Atlas to plot sites.

If you have been following the previous example, first clear old sites from the map by clicking the Clear Map button on the Atlas Tools window. Make sure that the current map is one of the black and white Outline maps, and that you have clicked Show Tools on the Atlas Tools window. Click the round button Select region.

For this exercise, a sparsely populated region was chosen because on a small scale map, the plotted sites tend to get overcrowded. By click-dragging the mouse, select an area approximately one inch square with the Bosporus at the center. (Hint: Plot the site of Byzantium if you do not know where the Bosporus is.)

When you release the mouse, the Sites in Region list will display the possible the sites the area. To plot the sites in the area you have selected, click Plot All Sites. To plot a particular site (or sites), click a site on the list, then click Plot Highlighted Sites.

The Compute Distance feature allows you to compute the distance in straight lines between two or more points on a map. It is available on both the black and white and color maps. Once again, if you have been following the previous example, first clear old sites from the map by clicking the Clear Map button on the Atlas Tools window. Make sure that the current map is one of the black and white Outline maps, and that you have clicked Show Tools on the Atlas Tools window. You will need to know how to use the Plot Sites in Area feature, described above.

Compute the distance of the paraplous from Iapygeum to Syracuse, via Kroton, Locri and Rhegion.

From the Outline map and with the Atlas Tools open, plot the sites Iapygean, Kroton, Locri, Rhegion and Syracuse.

Click the round button Compute Distances located on the Atlas Tools window. Notice that when you move the mouse over the map, the cursor now changes to a cross-hair. The Atlas has changed to Compute Distances mode, during which you will not be able to plot sites. To return to Plot Sites mode, click the round button Plot Sites on the Atlas Tools window.

Move the mouse to the map. To begin the "Trip," single-click on the site of Iapygeum. As you drag the mouse to Kroton, a red line will follow you. Single-click on Kroton. Continue this procedure with Lokri and Rhegion, making a dog-leg around the toe of Italy. When you get to Syracuse, double-click to end the Trip. At this time the red line turns black. The milage of your Trip will be logged in the upper field of the Atlas Tools window. Note that the endpoint of your Trip is indicated by an arrow head. You can return to the map and make any number of Trips, and you can compute the distance of a Trip with any number of legs, limited only by the amount of available memory. They will be logged sequentially, and if the field fills up, you can move around with the directional arrows.

N. B. When you single-click to begin a Trip, you are enabling a distance computation feature that measures the distance along a series of points. These points are wherever you click the mouse, whether plotted sites or white space. Notice that when you are in the Compute Distance mode, the ability to link to the Lookup tool by double-clicking on a site is disabled.

The Atlas menu appears on the menu bar only when the Perseus Atlas is activated. The Atlas menu has five items which supplement the functions of the Atlas Tools window.

Choose Atlas Tools to call up the Atlas Tools window. This may be more convenient than dragging maps out of the way.

This utility finds all maps in Perseus containing a given site, and then goes to the desired map. It also plots all sites in the database associated with a given region.

Task: Choose Atlas Search from the Atlas menu.

This is the default setting. (If you were in Map Search (By Region), choose Site from the pop-up menu Index Type, upper right.) Type Phaleron into the field Look For and click Do Search (note: this function is case sensitive). Or, click the site from the scrolling field, lower left.

The results of your inquiry for the site Phaleron appear on the right. Click a theme on the list at the right to go to that map.

To plot sites in a region of the Greek world, choose Atlas Search from the Atlas menu, then choose Region from the pop-up menu Index Type, upper right. In the field Look For, type the name of the region you wish to locate, and click Do Search. Or, click a region from the scrolling field, lower left. On the right, Perseus will give you a choice of the Small or Large Outline map. Click either one, and Perseus will plot the sites in the desired region without showing site names.

The Digital Elevation Model (DEM) Key is for use in conjunction with the color Digital Elevation (color topography and hydrography) maps. It shows the range of colors used in these maps and their associated values of elevation. Choose DEM Key from the Atlas menu. Click the close button on the DEM Key to hide it.

This feature plots a list of the sites which you have stored in the Perseus Search Saver. Please read about the Search Saver, here. The following exercise will illustrate Plot Sites from Search Saver feature.

Task: Plot the Mint locations for coins in Perseus from the Archaic period.

Get a list of Mint locations by making a Browser search (the Browser is described thoroughly here.). In the Browser, click the round button Coins and choose the Search Topic "Period" from the pop-up menu, top center. The pop-up menu now reads Period. Further refine your search by clicking Archaic, at the top of the list. Set the left column of results to Mint. Put your results into the Search Saver by clicking its icon on the Navigator window.

Now bring up the Small Outline map by choosing Atlas from the Links menu. From the Atlas menu choose Plot Sites in Search Saver. Note where the sites from the Archaic period are concentrated.

The Search Saver temporarily stores a list of sites you have plotted on a Map. To go to a site saved on the Search Saver, double-click it, and Perseus will plot this site for you in the Small Outline map.

PC: Running both Netscape and IE simultaneoulsy at 2 windows each on the NEC Pentium computer with 16 Meg RAM, the effect was to slow down the Atlas a few seconds. If your machine senses a memory problem, it will flash the message, "Running out of virtual memory."

Mac: Your ability to use the full features of the Atlas depends on the amount of random access memory (RAM) in your computer and the memory partition allocated to Platform Independent Perseus. Color images and color windows require more memory than textual resources and black and white graphics. With a color-intensive resource such as the Atlas, more RAM and a fast computer will enhance its performance.

Every Macintosh with 5 MB RAM alloted to Perseus can run the basic Atlas, meaning the color/black and white Atlas features, though it is preferable to have at least 8 MB RAM. The Computing Distances feature uses memory quickly. To achieve efficiency in memory and speed, leave color windows open only for as long as you are using color views in the Atlas. When you are finished with the Atlas, you must close the color map window by clicking the close box in the upper left corner. To avoid memory shortages, however, close all color windows when you no longer need them.