The Perseus Atlas: Frequently Asked Questions List

Basic Use and Navigation Questions

1. How do I use the map controls?
2. How do I add features and sites to the map?
3. More navigation tools
4. What to do when things go wrong.

General Troubleshooting

1. I can't get the map to draw completely, what do I do?
2. Why can't I read all the site/feature labels, it looks like a few labels are missing?
3. Hey, my whole screen is green and I can't see anything!
4. Why is site X in the Y Ocean/Sea?
5. You're missing a lot of sites. Why don't you have X, Y, or Z in your atlas?

Technical Information and Data Sources

1. About the map server
2. Point Data
3. Topographical Features

1. How do I use the map controls

   The Navigation tools allow users to focus the map view on a particular geographic area. Navigation tools are located on the right hand side of the atlas interface. There are four navigation options:

   • Find more information about
   • Zoom In
   • Zoom Out
   • Pan View

   Find more information about : This tool can be used only when sites have been plotted on the map. If you would like to search the Perseus digital library for more information about a site you have plotted on the map, click on the radio button next to the Find more information about label. Then click on the yellow plot point of the site you would like information about.

   The Pereus Lookup tool will then display a list of resources that are available elsewhere in the digital library. Please note that there may not be any additional information about a particular site on the atlas and your search may yield no results.

   Zoom In : Allows users to zoom in for a closer view of a section of the map. To do this, click on the radio button next to the Zoom In label. You may also select a zoom factor fromthe adjacent popup menu. The zoom factor is the degree to which you will scale down the map extent. The default is 2, and you can select a number between 2 and 10.

   Once you have set the zoom factor, click your mouse over the location on which you wish to scale down. The map view will redraw at the new scale and will be centered at the point on which you clicked.

   Zoom Out : Allows users to expand the map view. To do this, click on the radio button next to the Zoom Out label. You may also select a zoom factor from the same popup menu located adjacent to the Zoom In navigation option. In this case the zoom factor is the degree to which you will scale up the map extent. You can select a number between 2 and 10. The map will not draw beyond its original extent.

   Once you have set the zoom factor, click your mouse over the location on which you wish to scale up. The map view will redraw at the new scale and will be centered at the point on which you clicked.

   Pan View : Allows users to change the center point of the map regardless of the zoom factor. If, for example, you would like to shift the map to a new location without changing the scale of the map, select Pan View from the drop down menu and click on the new area. The map will redraw with the new location as it's center point.

   You may also use the blue directional arrows located on the perimeter of the map image to move the map view North, South, East, West, North East, South East, North West, or South West.

2. How do I add features and sites to the map

   Legend : The legend menu displays a variety of features, such as lakes, rivers, and elevation data, that can be added to the map. The number and kinds of features will change depending on the scale of your map view. For example, Contour lines will become available for drawing after you have zoomed in to a certain degree.

   The following data is currently available for drawing (more data is forthcoming):

   1. Modern Political Boundaries: political boundaries, including labels for countries, islands, and other political entities.
   2. Modern Populated places: current regions of human habitation, including labels.
   3. Inland bodies of water: Perennial lakes, and water bodies
   4. Rivers and Streams: Perennial rivers and streams.
   5. Contour Lines: Lines corresponding to the elevation of the land.

   The following data layers are always available by default:

   1. Topographic map of the world: note that this map is available only up to a certain scale.
   2. World basemap: visible only when the map view is scaled beyond the resolution of the Topgraphic map.
   3. Major World Lakes.

   To draw features click the checkbox (or boxes) next to the feature name and then click on "Refresh Map."

   Placename Gazetteer : Two options are available for plotting sites on the map: Locate places on the world map, and Locate specific places in the current Map View.

   • Locate places on the world map : First slect Search Globally or Search this Map View, the former will reset the Map View to a map of the world and plot sites on the world map, the latter will only plot sites available in the current map view, that is, the map view you have on your screen. Once you have made your selection, type the name of the site(s) you wish to plot and hit the Enter or Return key on your keyboard. Multiple site names should be separated only by a comma.

   • Locate specific places in the current Map View : To draw a specific site click the checkbox next to the site name the site name and then click on Refresh Map.

     n.b. : note that more sites become visible as you scale down into the atlas. You will notice occasional slow reload times if there are a large number of sites available in the map view.

3. More Navigation tools.

   The arrows around the perimeter of the main map view allow users to 'slide' the map view along the points of a compass (N, NE, NW, E, W, S, SE, SW). Click on an arrow to move the map view in any direction.

4. What to do when things go wrong.

   If the map view does not draw properly, click on Refresh Map.
   To clear all topographic and site selections and preserve the scale of the mapview click on Clear Map
   If all else fails, click on New Map to start a new session.

1. I can't get the map to draw completely, what do I do?
   Internet Explorer sometimes has trouble drawing HTML tables properly. If you notice that the atlas interface is out of whack, or that the map view only partially draws, hit your web browser's Reload button. The interface should then redraw properly.

2. Why can't I read all the site/feature labels; it looks like a few labels are missing?
   To avoid overlapping labels the mapping program will usually only draw labels that do not obscure other site/feature labels. Keep zooming in on the area in which you are interested and the labels should appear.

3. Hey my whole screen is green and I can't see anything!
   You have zoomed in too far. Look at the Scale Bar at the bottom of the main map view to get some idea of the map scale. If the Scale Bar is missing or garbled, you have definitely zoomed in too much. Just zoom out a few times and you should begin to recognize where you are in the world. Alternatively, hit New Map to start over.

4. Why is site X way out in the Atlantic Ocean?
   There are a couple of reasons for this. A very few sites were incorrectly entered in our database and are rendered at geographic coordinates (0,0). These errors will be corrected as we update our database.

   The second class of coordinates that exhibit this problem appear close to shorelines. Formiae, for example, will appear just off the shoreline of where it should belong. This is a data quality issue.

   Much of our data has been collected from USGS Gazetteers that register low-resolution geographic coordinates. Low resolution data means that geographic coordinates are recorded in Degrees and Minutes and not Degrees, Minutes, and Seconds, which is a more precise way of recording latitude and longitude (data with this type of accuracy is more difficult to obtain).

   Since our current dataset lacks minutes, most of our geographic coordinates are accurate up to 100 feet (in geographic terms one second is approximately 100 feet).

5. You're missing a lot of sites. Why don't you have X, Y, or Z in your atlas?
   The quality and quantity of information that makes up the Perseus atlas will improve over time as we acquire more data.

   The best way to improve the atlas is to help us. If you have GIS data that you would like to publish and incorporate in to the atlas, please visit the Stoa Consortium web site's Waypoint Database and read the Guide to Recording Handheld GPS Waypoints, or contact Robert Chavez (rchavez@perseus.tufts.edu) about contributing data for the atlas.

1. About the map server
   The Perseus Atlas interface was written in Perl and uses MapServer for image processing and dynamic delivery of geospatial data. MapServer is an OpenSource Internet GIS application developed by the University of Minnesota in cooperation with NASA and the Minnesota Department of Natural Resources. For more information about MapServer please vist the MapServer web site http://mapserver.gis.umn.edu/index.html

   Geospatial data is stored in PostGreSQL, an OpenSource database. For more information about PostGreSQL please visit the PostgreSQL web site http://www.postgresql.org/

2. Longitude, Latitude Coordinate Data
   The latitude and longitude coordinates for all the ancient sites in the Perseus site database have been collected from various USGS and National Imagery and Mapping Agency (NIMA) over the past 10 years,and more recently, the Getty Thesaurus of Geographic names. As we rebuild our geocoordinate database we will hopefully improve on the accuracy of our data and expand the range of our data beyond Greece and Italy proper.

   If you are interested in contributing data for the atlas please contact Robert Chavez at the Perseus Project: rchavez@perseus.tufts.edu

   More information is forthcoming, watch this space for details.

3. Topographical Features
   Topographical features have been collected from the National Imagery and Mapping Agency's Vector Map Level 0:
   

   Originator: National Imagery and Mapping Agency
   Publication Date: 1997 01
   Title: Vector Map Level 0 (Digital Chart of the World)
   Edition: 3
   Abstract (from the VMAP0 metadata file):
   
   ...VMap Level 0 is a comprehensive 1:1,000,000 scale vector basemap of the world. It consists of cartographic, attribute, and textual data stored on compact disc read only memory (CD-ROM). The primary source for the database is the National Imagery and Mapping Agency's (NIMA) Operational Navigation Chart (ONC) series. This is the largest scale unclassified map series in existence that provides consistent, continuous global coverage of essential basemap features. The database contains more than 1,900 megabytes of vector data and is organized into 10 thematic layers. The data includes major road and rail networks, major hydrologic drainage systems, major utility networks (cross-country pipelines and communication lines), all major airports, elevation contours (1000 foot(ft), with 500ft and 250ft supplemental contours), coastlines, international boundaries and populated places...