In an analogous manner to "Class of Survey", Order of Survey is a means of categorising the quality, or precision, of a static survey. However, it relates to the external quality, and is influenced by the quality of the "external" network information. The number of categories, the notation applied, and the accuracy tolerances defining the transition from one order to another are defined by individual nations. Typically they mirror the categories of Class of Survey, hence an A Class survey may correspond to a 1st Order survey. The labeling of a particular Order (e.g. 1st, 2nd, etc.) to a survey points within a "network" (whether it is carried out using GPS or any other technique) is performed as part of the process of Network Adjustment in which the relative error ellipses (in the horizontal case) between coordinated stations are computed and compared with the accuracy standards that must be met for various categories of Order. However, unlike the Minimally Constrained Network Adjustment that is a prerequisite to establishing the Class of Survey, the Network Adjustment must be constrained to the surrounding geodetic control. Hence a very high quality GPS network (therefore a high Class survey) may be distorted to "fit" the existing control which may have been determined using a lower Class survey. The resulting Order of the Survey would have to match the lower of either the Class of the GPS survey or the Class of the existing geodetic control. If the existing geodetic control is of a lower quality to what can be achieved using modern GPS Surveying techniques, then the geodetic control network must be upgraded or "renovated" using more precise GPS Geodesy techniques.