Spatial refers to giving a location to nodes, like answering the question, Where in the world is the new Dennis Ritchie?
Every location (or point) on Earth can be localized via its spatial coordinates--latitude and longitude. Both are angular values; they measure an angle from the center of Earth. Latitude zero is shared by all points on the equator. Positive latitude is for all points north of the equator. Negative latitude is for all points located south of the equator.
All points with the same latitude form a virtual horizontal line (circle); whereas all points with the same longitude form a line (circle) called meridian. Longitude zero is currently defined by the meridian going through Greenwich near London in the United Kingdom, where the royal observatory (not a people's magazine) is located. The legend says that the Greenwich meridian replaced the Paris meridian as longitude zero in exchange of England adopting the metric system.
Unfortunately, it has not worked...