GPS Survey Guidelines

PURPOSE: This rule prescribes the minimum procedures for first or second order Global Positioning System surveys. (1) Direct connections must be made to any adjacent observable National Spatial Reference System (NSRS) and/or Missouri Geographic Reference System (MO GRS) station located five kilometers (5 km) or less from any new station. (2) At least three (3) existing higher or equal order control points must be included in any proposed Global Positioning System (GPS) survey. Whenever possible these should be three (3) three- (3-) dimensional control stations. Otherwise two (2) sets of three (3) stations, (three (3) two- (2-) dimensional horizontal stations and three (3) vertical control stations) must be used. These control stations should be chosen to be roughly equidistant on the periphery of the proposed project so that they enclose as much of the project as possible. (3) Each new station to be established by the proposed GPS survey must be occupied at least two (2) separate times to enable proper checking of blunders (for example, incorrect point, setup errors, incorrect antenna heights). A separate occupation is one in which the antenna and its supporting device (tripod) have been taken down and set up again and the receiver restarted. (4) Each station must be connected by simultaneous occupations (baselines) to at least three (3) other stations in the network after outlier baselines have been rejected from the adjustment. Because it is generally easier to resolve the integer phase ambiguities over shorter baseline, adjacent stations should be connected wherever possible. (5) At least two (2) receivers must be used for relative positioning, although three (3) or more may be used for more efficient operation and increased station reoccupation and base line repeatability. (6) A preanalysis should be performed to determine the minimum occupation time required to achieve the required standard of accuracy. In addition, the most appropriate satellites to observe at each site should also be selected for receivers unable to track all of the “visible” satellites. The preanalysis should be specific for carrier phase relative positioning. (7) In order to meet second order accuracies, the carrier beat phase must be observed together with a time tag for each observation. Pseudo-range observations are not precise enough for control surveys and cannot be used. (8) A detailed field log must be kept during observation taken at each station. At the very least the following information must be recorded: (A) Universal Time Coordinated (UTC) date of observations; (B) Station identification (name and number); (C) Session identification; (D) Serial numbers of receiver, antenna, and data logger; (E) Receiver operator; (F) Antenna height and offset from monument, if any, to one millimeter (1 mm). Note should be made as to whether the height is measured as a slant height or vertical height; (G) Diagram illustrating stamping on the monument; (H) Other stations observed during session; (I) Starting and ending time (UTC) of observations; (J) Satellites observed (including time of changes); and (K) Completed field log data forms for each station occupation will be submitted either using those provided by the Missouri Department of Agriculture (MDA) or some other type containing all necessary information included on the MDA forms. (9) The raw data files for all station occupations must be submitted. Each file will consist of one (1) set of raw observations for each station occupation session. For example, four (4) receivers operating during each of five (5) sessions will produce twenty (20) raw data files. (10) The unadjusted baseline vector solution files for all observed baselines, non-trivial and trivial, will be submitted. (11) If station description information is not provided by MDA, it must be submitted for each station occupied. Station descriptions must include station name, county, township, range, section, United States Geological Survey (USGS) seven and one-half- (7.5-) minute quadrangle name, date monumented, date of observations, complete descriptions of the station, azimuth, and all reference monuments, a current “to reach” description, and any special information such as property owner name, address, and phone number. A sketch depicting the station and reference marks with dimensions and directions shown should accompany all narrative data. Examples of complete station description information may be obtained from MDA. (12) If the GPS survey project includes any surveys using conventional or terrestrial horizontal surveying techniques, copies of all field notes, and associated data must be submitted. This would include eccentric point establishment and reduction. Polaris, solar, or direct observational data to establish azimuth marks shall also be submitted. (13) When the GPS survey project includes surveys performed using conventional differential leveling techniques, copies of all field notes, and associated data must be submitted. An example of this would be a vertical tie from a nonoccupied bench mark to a GPS station. (14) A tabulation of the results of the repeat base line comparisons will be included in the project report. (15) A minimally constrained (free) least squares, three- (3-) dimensional adjustment will be submitted in the form of the input and output files. AUTHORITY: section 60.451.3., RSMo 2016.* Rule originally filed as 10 CSR 304.050. Original rule filed May 3, 1994, effective Dec. 30, 1994. Moved to 2 CSR 9062.050 and amended: Filed Dec. 1, 2016, effective June 30, 2017. *Original authority: 60.451.3, RSMo 1984, amended 2013.