Coordinate system concepts—This topic describes the basic concepts of coordinate systems used in ArcGIS Explorer and explains why coordinate systems are important.
How to convert measurements to different units—This topic describes how to convert a measurement in one unit to another, for example convert a 10 kilometers to miles, or a latitude of 51.54 in decimal degrees to degrees, minutes and seconds. It also describes some limitations of conversions.
How to define polygons and polylines—This topic describes how you can define polygon and polyline geometries by specifying individual vertices. It also describes how to define multipart polygons and polylines. A basic introduction to the concept of geometrical correctness or "simplicity" is given, with advice on when you might need to consider this.
How to project a geometry—This topic shows how to project a geometry from its existing coordinate system to another coordinate system, and when it is most appropriate to do so.