= Pleiades GPS Guide: What kinds of features and locations should I get coordinates for? =

 * ''back to the [wiki:GPSGuide Pleiades GPS Guide]''

== Pleiades Model Review ==

Pleiades '''places''' are composed of '''names''' and '''locations'''.

[[Image(ClassDiagram-1.png)]]

A '''location''' is a geo-temporal object. It has coordinates and its composition relationship with a place exists over one or more periods of time. In the Pleiades model "The Agora" is not a location. "The footprint (meaured with a certain accuracy) of the Agora (during period X)" is a location. Pleiades '''places''' originating from the Barrington's map-by-map directory come into being with a rough "Barrington Atlas location" that has no coordinates, only a Barrington map and grid cell reference (for example: "within the footprint of BAtlas map 1 grid G3"). We expect more accurate, more representative locations to be added by users over time.

The geometries of locations are 2D points, lines, or patches ''on the Earth's surface'' in the WGS84 coordinate system.

== Representative locations for settlements and similar features ==

For an ancient settlement or other extensive site, you may choose to provide only a single point location, or you can collect data for multiple locations on the site. Not being a building database, Pleiades is often well served by single point locations. Urbanization of a historically important place over time might be recorded by a point location at one time period succeeded by a polygon or patch at a later time.

When providing only a single coordinate pair, an effort should be made to find the rough spatial center of the visible remains of the site, unless these are dangerous, inaccessible or fragile. Then the nearest appropriate point should be selected. A recognizable key civic feature (e.g., agora, capitolium) may be chosen instead. Whatever point you choose, be sure to record an appropriate explanatory title that can be used when you upload the location into Pleiades.

For ancient settlements that are well-preserved or extensively excavated, you may wish to capture coordinates for multiple locations on the site. For example, you may capture the center-points of the forum, city gates, major temples, etc. Again, be sure to keep track of appropriate titles for each of these.

== Smaller features ==

Generally smaller places and locations (e.g., bridges, extra-urban monuments) require only a center-point reading.

== Linear features ==

Linear features, such as roads, walls, canals ...