Merge pull request #5 from davidhassell/coordinate-sampling-terminology

Terminology: interpolation variable and tie point variable

ch01.adoc

@@ -76,6 +76,8 @@ It is a one-dimensional variable with the same name as its dimension [e.g., **`t
 
 grid mapping variable:: A variable used as a container for attributes that define a specific grid mapping. The type of the variable is arbitrary since it contains no data.
 
+interpolation variable:: A variable used as a container for attributes that define a specific interpolation method for uncompressing tie point variables. The type of the variable is arbitrary since it contains no data.
+
 latitude dimension:: A dimension of a netCDF variable that has an associated latitude coordinate variable.
 
 local apex group:: The nearest (to a referring group) ancestor group in which a dimension of an out-of-group coordinate is defined. The word "apex" refers to position of this group at the vertex of the tree of groups formed by it, the referring group, and the group where a coordinate is located. 
@@ -103,6 +105,8 @@ sibling group:: Any group with the same parent group as the referring group
 
 spatiotemporal dimension:: A dimension of a netCDF variable that is used to identify a location in time and/or space.
 
+tie point variable:: A netCDF variable that contains coordinates that have been compressed by sampling. There is no relationship between the name of a tie point variable and the name(s) of its dimension(s).
+
 time dimension:: A dimension of a netCDF variable that has an associated time coordinate variable.
 
 vertical dimension:: A dimension of a netCDF variable that has an associated vertical coordinate variable.