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Government departments

Land and Property Information

Talk to LPI about their plans for topographic mapping in NSW

  • why are well-used tracks disappearing from maps? (eg Wollangambe tracks)
  • are they willing to take corrections/contributions from bushwalkers, and will they incorporate them?
  • [are they willing to license the data (not just the raster images) under a CC or similar licence?]
  • Contacts?
    • Garry Taunton
      • Team Leader Spatial Services
      • garry.taunton@lpi.nsw.gov.au
    • Tracie Walker
      • tracie.walker@lpi.nsw.gov.au

Privatisation of LPI

NSW Government is investigating the possibility of privatising LPI. Possibility of breaking the organisation down into branches. Need to investigate what the impact on mapping and access to spatial data may be.

http://www.rahs.org.au/land-and-property-information-to-consider-privatisation/

Update - 08 Jun 2016

It appears as though LPI will be broken down into three entities, with Titling and Registry Services (TRS) section of LPI privatised.

Thankfully Spatial Services, the entity relevant for mapping and spatial data, seems set to stay under public ownership.

However, the mapping section has already be moved from Prince Albert Rd Sydney, out to Bathurst. No longer can one walk into an LPI building in Sydney to make mapping related enquiries, or to look at aerial images through a set of stereo glasses.

Geographic Names Board

  • why are coordinates only accurate to the nearest minute in AGD66 co-ordinates? 1 minute is around 1.1km of latitude, and 0.93km of longitude (around Sydney). This means that the accuracy is presumably limited to half of that, or say +/-500m in each direction. For example, Mt Cloudmaker is around 500m from its correct position
  • AA spoke with GNB Secretariat (Susan Fietz - susan.fietz@lpi.nsw.gov.au) on the matter (27 April 2016):
    • What is on the GNB website is the official name places list
    • Updating of the list planned to start within the next few years
    • Any corrections are welcome
  • AA spoke with the Surveyor General (Narelle Underwood) on the matter (Jan 2017):
    • Acknowledged that the current system has its flaws are requires upgrading
    • Work is going to be done (timeframe not specified) on “bringing the GNR (Geographic Names Regester) into the 21st century
    • Many errors in the listed coordinates are due to the location being recorded in lat/long to the nearest minute but in the top left corner of the grid square, as opposed to the bottom left as convention dictates.

Licensing

Issues around

  • access to licensed DEM
  • if we use OSM data, it needs to be kept separate from other data or otherwise the other data needs to be released under the same licence

Historical maps

Topographic maps

  • 1:63360 (2 inch:mile)
    • 1st edition
    • 2nd edition (not all were revised
    • Note that the maps don't cover the whole of the state, they are mostly focused towards the coast. Also, there are a few 'holes' (eg Burragorang) where maps towards the coast were not published. This information is based on an index map held in the SLNSW which indicates which maps are in their collection, and it is assumed that they hold all maps which were published.
  • 1:31680 (1 inch:mile)
  • 1:50000 Army/RASC
    • 1st edition (ANG)
    • 2nd edition (AGD66/AMG)
  • 1:25000
    • AGD66/AMG - 1st edition & some 2nd edition
    • GDA94/MGA - some 2nd edition and 3rd edition (in some cases, 2nd edition is the latest)
    • Auto generated paper series (Question - Are these the same as the geopdf's available for purchase?)
    • Online vector map (appears to be different, but related to the auto generated series)

Map Series and Associated Map Sheet Identification

Other maps

  • Dunphy map collection
    • Large collection (>500) in SLNSW comprised of both published (~25) and unpublished
    • In some cases multiple editions of same map, especially those that were published
    • Majority of published maps scanned by AA from personal collections, also so unpublished ones
  • Other sketch maps
    • Various maps published by bushwalkers
  • Bushwalking guide book maps
    • Most guide books have maps in them, mostly sketch maps by author
    • Some are to scale and can be georeferenced, others (eg Jim Smith-How to See the BM) are not but still handy for routes and access

Data compilation

Datums

See http://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/geodetic-datums for more information on relevant datums for Australia.

What is a Datum?

[Brief explanation of datums. Possibly include a “datum vs projection - what's the difference?” section.]

http://www.icsm.gov.au/mapping/index.html

WGS84 (EPSG:4326)

Reference co-ordinate system used for GPS (Global Positioning System)

WGS84 Bounds: -180.0000, -90.0000, 180.0000, 90.0000
Projected Bounds: -180.0000, -90.0000, 180.0000, 90.0000
Scope: Horizontal component of 3D system. Used by the GPS satellite navigation system and for NATO military geodetic surveying.
Area: World

GDA94 (EPSG:4939)

GDA94 is the Australian representation of WGS84. There is almost no difference in a 2d sense (Australia has a separate height datum), at least from a bushwalking perspective.

WGS84 Bounds: 108.0000, -45.0000, 155.0000, -10.0000
Scope: Geodetic survey.
Area: Australia - all states

ICSM GDA Technical Manual

GDA94, ITRF & WGS84 - What’s the difference?

WGS – AGD – GDA: Selecting the correct datum, coordinate system and projection for north Australian applications

Other Datums

AGD66

The datum used on topographic maps before GDA94. 2nd Edition topographic maps use the AMG66 projection which is derived from AGD66.

Australian National Grid (ANG)

Prior to 1966 the ANG was used, which covers both the 1:63360 and 1:31680 maps topographic maps.

See http://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/geodetic-datums/historical-datums-of-australia/australian-national-grid

http://www.binaryearth.net/AusDatumTool/AustralianNationalGrid.html

The ANG makes use of the Clarke 1858 spheroid.

Datum Conversions

Conversion tool by Anthony Dunk - http://www.binaryearth.net/AusDatumTool/index.php

Projections

See http://spatialservices.finance.nsw.gov.au/surveying/geodesy/projections for more information on relevant map projections within NSW.

GDA94 / UTM (EPSG:see below)

There are three UTM projections of GDA94 relevant to NSW.

  • EPSG:28354: GDA94 / MGA zone 54 - UTM projection of GDA94 for zone 54
  • EPSG:28355: GDA94 / MGA zone 55 - UTM projection of GDA94 for zone 55
  • EPSG:28356: GDA94 / MGA zone 56 - UTM projection of GDA94 for zone 56

The Map Grid of Australia 1994: A Simplified Computational Manual

GDA94 / NSW Lambert (EPSG:3308)

Used by NSW GIS systems for whole of state projections.

WGS84 Bounds: 141.0000, -37.5000, 153.6200, -28.1500
Projected Bounds: 8709235.6860, 4009911.3943, 9951732.0554, 5048642.3129
Scope: Natural Resources mapping of whole State.
Area: Australia - New South Wales (NSW)

Web Mercator (EPSG:3857/EPSG:900913)

Used in many popular web mapping applications (Google/Bing/OpenStreetMap). Uses spherical development of ellipsoidal coordinates. Relative to an ellipsoidal development errors of up to 800 meters in position and 0.7 percent in scale may arise. It is not a recognized geodetic system: see WGS 84 / World Mercator (CRS code 3395).

Universal Transverse Mecator (UTM)

The international standard projection coordinate system. The parameters of MGA are identical to that of UTM, except that they differ in spheroid (GRS80 vs WGS84)

http://www.uwgb.edu/dutchs/FieldMethods/UTMSystem.htm

Ellipsoids

An ellipsoid (sometimes referred to as a spheroid) is a simplified mathematic representation of the Earths shape. A spheroid can be defined by two parameters, typically: the semi-major axis (alpha) and the inverse flattening (1/f)

The below table summarises relevant values for common spheroids.

http://spatialservices.finance.nsw.gov.au/surveying/geodesy/projections

Parameter Clarke 1858 ANS GRS80 WGS84
Major Semi Axis 6378293.645 6378160 6378137 6378137
Inverse Flattening 294.26 298.25 298.2572221 298.2572236
Used in ANG AGD, AMG GDA, MGA GPS

Further information on geodesy can be found here - myGeodesy

Prominence

What is it?

In the geographical context, the prominence of a mountain is the elevation differential between the mountain’s summit elevation and its highest pass/saddle connecting it to its parent.

http://www.surgent.net/highpoints/prominence.html

It is of use to bushwalkers as it provides an indication of relative difficulty in the effort required to reach a peak. By applying among other things a prominence criteria, a list of peaks that meet that criteria can be complied. An example is The Abels of Tasmania, where only peaks over 1100m altitude but with a prominence greater than 150m are included.

The prominence criteria is important as it removes high peaks that are near to each other in altitude and would require little elevation gain to travel between them.

How is it calculated?

braindump.txt · Last modified: 2017/02/08 06:02 by allchin09