7.20 'As Constructed' Requirements for Digital Survey Information
- 7.20.1 Overview
- 7.20.2 Melbourne Water's criteria for accepting digital survey data
- 7.20.3 General rules for structuring the digital survey data
- 7.20.4 Melbourne Water's preferred formats and projection
Overview
Melbourne Water's Geographical Information System (GIS) is based on MapInfo and Hansen (Melbourne Water's Asset Management System). The graphical data is stored in MapInfo tables with attribute data stored in Hansen. Melbourne Water expects graphical data only, there is no requirement for attribute data (i.e. pipe size, material, etc).
The intent of the digital data is to provide asset locational information in respect to title, so that Melbourne Water can easily consolidate this information into its GIS. Melbourne Water's geographical data is currently based on MGA94(z55).
Melbourne Water requests that any digital information created or captured during the preparation of 'as constructed' information and which conforms to the criteria stated below, be submitted as part of the 'as constructed' information. Provision of digital survey data is not an alternative for the mandatory submission of annotated 'digital design plans' - it is in addition.
Melbourne Water's criteria for accepting digital survey data
- Digital survey data that represents the geographical location of the 'as constructed' Works in respect to title boundaries
- The 'as constructed' information for both design plans and digital survey data should be in the same projection.
- The minimum requirements for digital survey data, is the 'as constructed' location of all assets, including relationship to title boundaries with surrounding mapbase, by offsets and MGA94(z55) coordinates. Any other information recorded by the Consultant/Surveyor for their purposes will also be accepted.
General rules for structuring the digital survey data
- To enable Melbourne Water to easily consolidate the provided digital survey data into its Geographical Information System, all relevant points of interest (i.e. tangent points, changes of grade, centre point of manholes, changes in horizontal direction) should have a vertex placed or be one of the end points of a line string.
- Spot levels must show the point at which the level was taken
- The centreline of all linear constructed works should be shown (i.e. pipe centreline, channel centreline and levee bank centreline)
- For channels, the toes, top of cuts and any ramps or beams are to be shown
- For levee banks, both tops and toes are to be shown
- For retarding basins and wetlands, features such as lakes and earthen mounds are to be shown as well as spot levels and generated contours where appropriate (i.e. spot levels may be more appropriate than cross sections).
- For assets such as lakes, wetlands and retarding basins, the Normal Top Water Level (NTWL) must be shown.
- A limited amount of text is required to assist with interpretation, such as manhole numbers, descriptions of unusual features, or road names
- Line strings may be used to identify the location of 'as constructed' cross sections
- Melbourne Water does not require information linkages to be attached to graphical objects/elements nor wishes to specify specific symbology (i.e. levels/layer names, colours, weights, styles, fonts, text size, etc.) that must be used. The intent of not imposing these requirements is to ensure that no software development is required within the Development Industry and to allow consultants to continue to maintain their own internal standards. Consultants also do not need to contend with obtaining Melbourne Water's font libraries, cell libraries, code lists or colour tables.
Melbourne Water's preferred formats and projection
The following details do not constrain the consultant on how they prepare or capture the digital information, but provides Melbourne Water's preferred formats that will assist Melbourne Water in consolidating the 'as constructed' information into its Geographical Information System.
Preference 1 - MapInfo format (Version 8)
Melbourne Water's Geographical Information System is MapInfo/Hansen IMS. Melbourne Water's MapInfo files are on the MGA94 (z55) projection with its bounds/working area set with an easting range of zero to one million metres and a northing range of 5.5 million to 6.5 million metres. Setting the bounds as stated allows for data to be stored within MapInfo tables to a precision of one millimetre. Not setting the bounds does not hinder Melbourne Water in its requirement to incorporate the 'as constructed' information into its Geographical Information System, but does decrease the storage precision to between 0.01m and 0.02m, which is still adequate for meeting required tolerances.
Preference 2 - MID/MIF format
This is an ASCII format that can be imported directly into MapInfo format with associated attributes. The format is published and is available on request from Melbourne Water. Once again Melbourne Water requires the projection to be MGA94 (z55) with bounds/working area set with an easting range of zero to one million metres and a northing range of 5.5 million to 6.5 million metres.
Preference 3 - Microstation format (Version 8)
Although Melbourne Water will accept the digital data in Microstation format in either 2D or 3D, Melbourne Water's preference is that the files are structured as follows:
- global origin set at 214748.3648, 214748.3648.
- working area set at:
- master units = m (metres)
- sub units = mm (millimetres)
- resolution = 1000 sub units to a master unit
- one position unit = 1 mm
- these working units allow for one millimetre precision
A Microstation seed file providing this structure with relevant colour palette is available on request from Melbourne Water.
Preference 4 - AutoCad (2006 or earlier)
Co-ordinates provided in AutoCad format must be in accordance with a known published projection or for arbitrary co-ordinates, Melbourne Water's preference is to have eastings within the range of zero to one million metres and northings within the range of 5.5 million to 6.5 million metres.
Preference 5 - DXF format
DXF format is a common interface for most geographical software packages and as such provides a format that can be readily created by the consultant/surveyor and received by Melbourne Water. Co-ordinates provided in DXF must be in accordance with a known published projection or for arbitrary co-ordinates, Melbourne Water's preference is to have eastings within the range of zero to 1 million metres and northings within the range of 5.5 million to 6.5 million metres.
