Metadata : Northern Territory Geodetic Survey System - Survey Control

Index:


Metadata Details:

Name: AS/NZS ISO 19115 Geographic Information - Metadata, ANZLIC Metadata Profile

Version: 1.0

Date Metadata Extracted: 2019-11-14

Date Metadata Last Updated: 2017-02-10

Current URL (HTML format) : http://www.ntlis.nt.gov.au/metadata/export_data?type=html&metadata_id=34944E3BF675F2CDE050CD9B2144225D

Current URL (XML format) : http://www.ntlis.nt.gov.au/metadata/export_data?type=xml&metadata_id=34944E3BF675F2CDE050CD9B2144225D


Citation

ANZLIC Identifier: 34944E3BF675F2CDE050CD9B2144225D

Title: Northern Territory Geodetic Survey System - Survey Control

Citation Date:

Date Type:

Custodian: Department of Infrastructure, Planning and Logistics


Description

Abstract:

The dataset contains an extract of survey control information derived from the Survey Marks Data Base, the current repository for the Northern Territory Geodetic Survey System (NTGESS), created and maintained by the custodian, Survey Services, Land Information Division. The primary function of NTGESS is to maintain the official record of horizontal and vertical survey control data, and as such this extract includes positional, height and other information such as locality sketches.

ANZLIC Search Words:

Spatial Domain:

Bounding Coordinates:


Dataset Status

Dataset ID:

Language: English

Character Set: Latin 1

Progress: onGoing

Maintenance and Update Frequency: continual

Data Currency Start Date: 2016-06-06

Data Currency End Date:

Access Constraint: The data is freely available and accessible to all interested parties.


Data Quality

Lineage: The survey control information has been collated from various sources in order to realise a geodetic framework for the Northern Territory, underpinning all other spatial data:

- The custodian has primarily been involved with the physical installation, coordination, mathematical adjustment, maintenance and reporting of the survey mark and associated information;
- Private contractors/Surveyors have jointly taken responsibility for the physical installation, coordination and maintenance of survey marks and associated information.

The coordinates provided for a survey control mark may be the result of a rigorous Least Squares Adjustment, with some level of confidence associated with the results. Other coordinates which have not been 'processed' in this way may be scaled or approximate, or derived from GNSS survey methods such as Real-Time-Kinematic .

The 'status' of a survey mark indicates the certainty of the stated coordinate (see 'positional accuracy').

Positional Accuracy: The 'Status' of a survey mark provides an indicative confidence estimate of the HORIZONTAL positional uncertainty, where:
- Adopted - The coordinates of the mark have been adjusted as part of a larger network adjustment (+/-30mm horizontal positional uncertainty)
- Approved - the coordinates for the mark have been submitted to, and validated by the custodian (+/- 30mm horizontal survey uncertainty)
- Lodged - the mark has been physically placed in the ground, established via cadastral survey and in most cases shown on a cadastral plan with the bearing and distance connection to cadastre reported (+/- 20m positional uncertainty)
- Proposed - a unique identifier has been allocated and coordinates are approximate/digitized only (+/- 100m positional uncertainty)
- Disturbed - the mark has been reported as physically disturbed, verified by cadastral connection or comparison of coordinates
- Gone - the mark has been reported as "gone"

All benchmarks assume the status of "Lodged" only, as the quoted coordinate is approximate only, having been digitised from a legacy BM index map.

Attribute Accuracy: Survey mark attribute information is updated by the Custodian as and when required. Private Surveyors support the ongoing maintenance of records within NTGESS, through lodgement of an NTGESS spreadsheet detailing metadata for each survey mark established or visited. These spreadsheets are verified and then imported directly into the NTGESS / Survey Marks Database (SMDB), updating each record accordingly.

The accuracy of the qualitative survey information is unable to be qualified.

Logical Consistency: The dependability of relationships within the dataset are maintained and highly correlated.

Completeness: The survey mark information included in the dataset is used in the realisation of a Geospatial Reference System (GRS), providing a sound geodetic framework for spatial data users in the Northern Territory. The custodian is currently involved with a national datum modernisation program, during which the completeness, maintenance any relevancy of discrete records within the NTGESS will be assessed.

The accuracy of the qualitative survey information is unable to be qualified or estimated.


Contacts

NameOrganisationPositionRolePhoneFaxEmail
Department of Infrastructure, Planning and LogisticsSurveyor Generalcustodian(08) 8999 6081(08) 8999 7750robert.sarib@nt.gov.au

Data Dictionary

AttributeAttribute DescriptionPossible CodeCode Description
Adjusted RLThe reduced level for a survey mark, as observed, adjusted, recorded and maintained with respect to known benchmarks and the AHD71 vertical height datum. The vertical accuracy statement for NTGESS is based on the legacy hierarchy for survey accuracy of Class C, Third Order.
Derived RLThe vertical height or 'level' for a survey mark, where for example, observations such as those from GNSS have been reduced using a geoid model, and the derived value is an approximation of, or direct reference to the AHD71 vertical reference datum. Vertical uncertainty is quoted with respect to AusGeoid09, which is in the order of 0.3m.
Easting / NorthingThe Map Grid of Australia coordinates (grid) projected from GDA94 latitudes and longitudes (geographic coordinates).

MGA94 coordinates have a false easting of 500,000m and false northing of 10,000,000 m.
Latitude / LongitudeThe geographic coordinates defined by the Geocentric Datum of Australia 1994, a realisation of the International Terrestrial Reference Frame 1992 (ITRF92) at epoch 1994.0

The latitude and longitude coordinates in this dataset are provided as 'Decimal Degrees'
Locality sketchA sketch showing the location of a survey mark with respect to roads, street furniture, recovery marks and the cadastre, assisting a Surveyor to physically locate/ recover the mark efficiently in the field.

The features will typically be referenced using a horizontal ground level distance and magnetic bearings.

The locality sketches are static in time (fixed at the date of lodgement or creation), and are not routinely updated unless a Surveyor lodges an amendment or a revised sketch.
LocationThe official location or locality to which the survey mark can be referenced based on its stated coordinate data
Name- The marks unique identifier supplied by the Department during the data allocation process.
- In 90% of cases they will be in the format of prefix S or L (depending on the type of survey plan) followed by two digits for the year, three digits for the plan number and finally three digits for the CRM number. For example, a CRM (and series) established on survey plan S2016/005 with be labelled sequentially S16005001, S16005002, '03, etc.
- No spaces and no special characters are to be used within the primary name.
- The prefix 'CRM' should not be used in front of the unique identifier. For example survey mark S11068002 is NOT written as CRM S11068002.
StatusThe survey mark 'Status' is a classification based on Horizontal Uncertainty / Positional accuracy, where each classification is defined as follows:

- Adopted - The coordinates of the mark have been adjusted as part of a larger network adjustment (+/-30mm horizontal positional uncertainty)

- Approved - the coordinates for the mark have been submitted to, and validated by the custodian (+/- 30mm horizontal survey uncertainty)

- Lodged - the mark has been physically placed in the ground, and in most cases shown on a cadastral plan with the bearing and distance connection to cadastre reported (+/- 20m positional uncertainty)

- Proposed - a unique identifier has been allocated and coordinates are approximate/digitized only (+/- 100m positional uncertainty)

- Disturbed - the mark has been reported as physically disturbed, verified by cadastral connection or comparison of coordinates

- Gone - the mark has been reported as "gone"

TypeCoordinated Reference Mark (CRM) - a mark as described by the Surveyor General in the Survey Practice Directions; typically a brass plaque in concrete or star iron driven to refusal with concrete collar; recoverable (2 recovery marks)

Coordinated Mark (CM) - a mark that has been coordinated but does not meet the minimum requirements as set out by the Surveyor General in the Survey Practice Directions; may be a star iron or peg; typically no recovery marks

Benchmark (BM) - a mark used for the realisation of, and transfer of reduced levels. Typically in the Northern Territory these are referenced to the Vertical reference datum AHD71

Continuously Operating Reference Stations (CORS) - a base station that provides Global Navigational Satellite System data supporting three-dimensional positioning and science applications. The CORS contribute to a National and regional networks
ZoneThe zone in which the Grid Coordinates (based on UTM) are located for a particular survey mark.

Supplementary Information

The identity and stability of a Survey Control Mark must be verified in accordance with established survey best practice, before placing any reliance on the coordinates or height of a mark. The Northern Territory Government will not be held responsible for any loss that might result from the erroneous identification or instability of any Survey Control Mark, or inaccurate or unverified reporting of information pertaining to the mark. Whilst every effort is made to validate the accuracy and integrity of data contained in this dataset, it is derived from a variety of sources, some of which are outside the control of the custodian.

This record maintained using the NTLIS Metadata Tool