Input Dataset

Survey Control Information Management System

Theme

Positioning

Jurisdiction

NSW

Custodian

Control Survey Mark references are recorded within the Survey Control Information Management System (SCIMS). This is a database that contains all of the coordinates, heights and related information for NSW survey marks that form the official State Survey Control Network. The network is represented physically by over 240,000 permanent ground marks including over 6,300 beaconed trigonometrical Read More »

Metadata Address

https://sdi.nsw.gov.au/catalog/search/resource/details.page?uuid=E26CE89B-3DC6-4…

Dataset Purpose

The Survey Control Information Management System (SCIMS) is a reliable and accurate spatial referencing system that underpins cadastral boundary definition, engineering surveys, mapping and a variety of other spatial applications. The database is frequently utilised for asset management, establishing property boundaries and constructing public infrastructure. The mark classes have varying degrees Read More »

Funding Support

Access Mechanisms

Registered users through SCIMS online portal. Limited over the counter and telephone services, MOU - bulk supply etc

Dataset Lineage

Survey marks are tied to the MGA co-ordinate reference system and assigned a class, commensurate with their designed and achieved precision. Class is a function of the precision of a survey network, reflecting the precision of observations as well as suitability of network design, survey methods, instruments and reduction techniques used in that survey. The class is verified by an analysis of the Read More » minimally constrained least squares adjustment of the network according to ICSM (2007). Survey Marks are assigned an order (or positional uncertainty) and can be assigned a local uncertainty to clearly describe the accuracy of the positions. Order is the uncertainty of the coordinates or height of a point, in metres at the 95% confidence level, with respect to the defined reference frame. Local uncertainty is the average measure, in metres at the 95% confidence level, of the relative uncertainty of the coordinates, or height, of a point(s), with respect to the survey connections to adjacent points in the defined frame. The assigned horizontal class determines the specific applications for which the co-ordinates can be used. Typically, “3A” marks are used for special high precision surveys, “2A” marks are used for high precision national geodetic surveys, “A” marks are used for national and State geodetic surveys, “B” marks are used for densification of geodetic survey and state survey control networks, “C” marks are for survey coordination projects, and cadastral control surveys, “D” marks are for lower class projects and cadastral and other surveys, “E” marks are for lower class projects and “U” marks are approximate horizontal positions of unreliable accuracy . Survey marks are also tied to the AHD71 vertical reference datum and in some cases also the GRS90 reference datum. Heights are assigned different types of class and order according to the heighting technique used. Heighting techniques such as differential levelling propagate errors in proportion to the square root of the distance. Other techniques such as GPS and trigonometric levelling propagate errors mainly in proportion to the distance. This is particularly apparent on distances greater than 1 km. Refer to ICSM SP1 (2007) for details of observation techniques. The assigned a vertical accuracy classification associated with its accuracy to AHD71 and or GRS90; “L2A” refers to precise levelling with forward and backrun misclose < 2√d (where d refers to distance in kilometres), “LA” refers to 1st order levelling with forward and backrun misclose < 4√d, “LB” refers to 2nd order levelling with forward and backrun misclose < 8√d, “LC” refers to 3rd order levelling with forward and backrun misclose < 12√d, “LD” refers to levelling with forward and backrun misclose < 18√d, “LE” refers to levelling with forward and backrun misclose < 36√d, “2A” refers to precise trigonometric or GPS heighting with standard deviations of observations < 3 (d+0.2) mm, “A” refers to trigonometric or GPS heighting for state survey control with standard deviations of observations < 7.5 (d+0.2) mm, “B” refers to trigonometric or GPS heighting for cadastral control with standard deviations of observations < 15 (d+0.2) mm, “C” refers to trigonometric or GPS heighting with standard deviations of observations < 30 (d+0.2) mm, “D” refers to trigonometric or GPS heighting with standard deviations of observations < 50 (d+0.2) mm, “E” refers to trigonometric or GPS heighting with standard deviations of observations < 100 (d+0.2) mm, and “U” refers to approximate vertical positions of unreliable accuracy. The status of survey marks is also reported as destroyed, disturbed, not found, found, restricted access and mines subsidence area. All submissions to update SCIMS with control survey data are required to include a Survey Report and Locality Sketch Plans for all marks placed. Accuracy statements (class and order) are assigned to each horizontal position and height. Public and private sector surveyors (including LPI’s surveyors) contribute to the currency of the network by placing and surveying new permanent survey marks that extend the network on the ground. The Board of Surveying and Spatial Information (BOSSI) ensures competency standards for surveyors and surveying practices are met in NSW. Access to survey mark data within SCIMS is available through the SCIMS Online internet product (the delivery portal for SCIMS). Survey marks are displayed on a digital mapping screen and are colour coded according to GDA and AHD accuracy, where established GDA and accurate AHD is represented as a red icon, established GDA only represented as a purple icon, accurate AHD only represented as a green icon, and unknown or less accurate GDA and AHD is represented by a light blue icon. Established GDA coordinates are assigned accuracy class 2A, A, B or C and accurate AHD heights are assigned accuracy class L2A, LA, LB, LC, LD, 2A, A, or B. The survey marks within SCIMS Online are also assigned a shape coding according to the mark type; where Permanent Mark (PM) is a square with a border, State Survey Mark (SS) is a circle with a border and Trigonometrical Station (TS) is a triangle with a border , Geodetic Bench Mark (GB) is a star, Miscellaneous Survey Mark (MM) is an “+” symbol, Mapping Control Point (CP) is assigned as a circle around a “+” symbol, Cadastral Reference Mark (CR) is a inverted triangle. « Less

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