ABOUT NATMAP RASTER

VERSIONS

2003 - Mapsheets and Mosaic

In 2003 two versions of NATMAP Raster were released. The differences are outlined below.

• Mapsheets: all 513 1:250,000 scale NATMAPs plus three map insets are included as separate ECW files. The 1:250,000 scale maps use the Map Grid of Australia as their projection, meaning that the coordinates of the maps are measured in metres and the maps can be used for measuring distances and areas. Pixel size is 31.75m.
• Mosaic: all 513 1:250,000 scale NATMAPs plus three map insets are joined together in one ECW file. The coordinates are latitude/longitude, which are ideal for interfacing with GPS software, but are not suitable for measuring distances or areas. The pixel size in metres varies depending where you are in Australia. Mosaic also includes a single map image of all 1:1,000,000 NATMAPs and a Landsat Satellite Image Mosaic of Australia, both of which use latitude/longitude coordinates.

Updated features for 2003

1. Inclusion of over 150 new maps
2. All 1:250,000 scale maps are created to the same specification (i.e. have the same look and feel)
3. Mosaic version - all 1:250,000 scale NATMAPs joined together into one image
4. Inclusion of 1:1 million and Landsat satellite imagery (Mosaic only)
5. Popup windows for legend and climate graphs
6. More comprehensive User Guide, troubleshooting and Basic Help

1. Updated maps from 2002
   
2. Image resolution of 200dpi
   
3. Access to grid coordinates
   
4. Improved georeferencing
   
5. Raster Viewer Configurator tool
   
6. Bulk exporting
   
7. Available on Windows 95, 98, 2000, XP, Me or NT4.
   
8. User interface via IEv5.5 or higher.
   
9. Map loading via latitude and longitude.
   
10. Panning from map to map.
11. Finding the latitude and longitude coordinates of a point on the map.
    
12. Printing the entire map or the current view.
    
13. Exporting the entire map or current view; JPEG, BMP, PNG, TIFF and GeoTIFF image formats are supported.
    
14. Online help file that can be read on screen or printed as needed.
    

All other components in the two products are the same as in previous versions.

Are upgrades available?

At this stage no - if you want updated maps and/or Viewing software, you need to buy the new version.

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PRODUCT COMPONENTS

NATMAP Raster products are made up of the following components.

• this Product User Guide and associated documentation

• digital map images (*.ecw format). These are organised into layers, with each layer equivalent to a specific map series, scale or product. The number of map images you receive will depend upon which particular NATMAP Raster product you have purchased.

  Further information on the images that make up each layer may be found in Map Layers and Image Specifications.

• software for viewing, exporting and data management. The NATMAP RASTER VIEWER is the software in this package that is used for selecting and viewing maps. The stand-alone RASTER EXPORTER can be used to export the ECW map images into other graphic formats such as GeoTIFF, TIFF, JPEG, Windows Bitmap and PNG. The RASTER CONFIGURATOR allows you to manage where your maps are stored, so you are not restricted to storing all maps in the one location.

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Landsat 7 Satellite Image of Australia (Mosaic only)

Layer ID in the Raster Viewer: "Satellite Mosaic"

The Landsat 7 Picture Mosaic of Australia was produced by the Australian Greenhouse Office (AGO) as part of their National Carbon Accounting System. The mosaic is comprised of 369 individual Landsat satellite scenes acquired between July 1999 and September 2000. For more information on the Landsat 7 satellite, refer to the Satellite Remote Sensing pages on the Geoscience Australia web site.

1:250,000 scale topographic map series (Mapsheets and Mosaic)

Layer ID in the Raster Viewer: "250K Maps" (Mapsheets); "250K Mosaic" (Mosaic)

The NATMAP 1:250,000 scale maps included in this NATMAP Raster product have been produced by Geoscience Australia's National Mapping Division and its predecessor, the Australian Surveying and Land Information Group (AUSLIG), in conjunction with the private sector. This is the largest scale at which published topographic maps cover the entire continent. The maps have been revised using a variety of data sources, including SPOT and Landsat satellite imagery, other government agency information, and data supplied by private companies and individuals. Production of the new NATMAP series began in the early 1990s, and concluded in 2003.

For more information, please refer to the 1:250,000 scale NATMAP legend explanation. Additional information on map specifications, new maps and the current status of NATMAP revision can be found on the Topographic Mapping pages on the Geoscience Australia website.

1:1,000,000 scale topographic map series (Mosaic only)

Layer ID in the Raster Viewer: "1M Mosaic"

The International Map of the World (IMW) Australia series was Australia's contribution to a common effort by many international mapping agencies to map the world at 1:1,000,000 scale. It was initially conceived for planning economic development but has been used as the basis for many other maps including aeronautical charts and thematic mapping. The series was completed in 1978 and was revised regularly until the mid-1980s.

Small scale reference maps (Mapsheets and Mosaic)

Layer ID in the Raster Viewer: "5M Map"

The smaller scale general reference maps provide a general overview of Australia, but still contain similar information to the larger scale maps. These maps have been regularly revised since the mid-1990s, and revision information is sourced from the same sources as the 1:250,000 scale maps. The Locator map used here is derived from GEODATA TOPO-10M, which is freely available from the Geoscience Australia website. The 1:5,000,000 scale General Reference Map of Australia is used for the 5M Map layer and the Magnifier map.

Topographic Map Index (Mapsheets and Mosaic)

The NATMAP Map Index shows which maps cover which areas. The version of the NATMAP Map Index used in NATMAP Raster is slightly different from the printed version. The version included here does not show 1:100,000 scale maps and combines the 1:1,000,000 and 1:250,000 scale maps into the one map in order to make viewing easier. The 1:9 million Compact Reference Map has been used as a base.

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Information on coordinate systems can be found in the coordinate system pages.

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CREATION PROCESS

The images used in this version of NATMAP Raster are derived from the most current edition of the respective maps available from Geoscience Australia's Map Sales as at August 2003. A full list of the currency of all layers and individual maps in the NATMAP Raster product is included in this User Guide.

"Raw" raster images were created from the digital EPS files used to produce the new NATMAP paper map series. Where digital EPS files were not available, the paper map was scanned to generate the "raw" raster images. Each "raw" raster image was transformed to be positionally accurate and encoded with coordinates and projection information before being compressed in the final ECW image.

The content of some 1:250,000 scale maps may differ from the printed map. Maps marked with an asterisk (*) after the edition number in any drop-down menu have been created from digital data that has not fully met NATMAP specifications; however, the content and structure of these maps are close enough to final specifications to be included in this product. Maps covering Tasmania have been produced from digital data; however, printed versions of these maps are not yet available.

Maps which may differ from the final printed version are:

• SD51-12 MONTAGUE SOUND SPECIAL
• SD51-16 PRINCE REGENT
• SE52-11 BININDUDU
• SE52-14 BILLILUNA
• SF51-06 PATTERSON RANGE
• SF51-07 SAHARA
• SF51-11 TABLETOP
• SF51-14 GUNANYA
• SF52-01 CORNISH
• SF52-02 LUCAS
• SF52-06 STANSMORE
• SK55-20 TASMANIA NORTH-WEST (including KING ISLAND)
• SK55-21 TASMANIA NORTH-EAST
• SK55-22 TASMANIA SOUTH-WEST
• SK55-23 TASMANIA SOUTH-EAST

Some features on maps, especially small scale maps, are subject to what is known as cartographic generalisation. It refers to a group of techniques used by map makers which allow the level of information to be retained, while the amount of data shown on the map is reduced.

These techniques include:

• pre-selection
• reshaping or smoothing lines
• removing small features
• aggregating many small features into a few large features, eg showing a group of buildings as a single building
• selecting certain features that maintain an overall shape, eg reducing the number of streams in a stream network without losing the overall pattern of drainage
• enlarging important features which may otherwise be too small to show
• moving features relative to each other (displacement)

Features may be located on the earth’s surface in such a way that they cannot be separated at the scale of the map. To make sure that the map is readable, one feature is kept in its true position, and the rest are displaced.

In NATMAPs, the following features may be displaced when one or more are adjacent. The higher a feature is on the list, the more likely that it has been held in the correct position over those lower on the list.

1. hydrographic lines such as coastlines, watercourses and lakes
2. railways
3. principal roads
4. secondary roads
5. minor roads
6. tracks
7. buildings
8. vegetation boundaries

If two features need to be offset to one another and neither is listed, the position of the feature with greater landmark value will be maintained.

For example, if a railway and road are coincident at the scale being produced, the road would be displaced. Where two or three features are close and adjacent, one may be displaced by up to 225 metres at 1:250 000 scale. In the worst case when all these features are close together, one may be displaced by up to 675 metres at 1:250 000 scale. However, any features that have been displaced must maintain their relative position. See the picture below.

This extract from the Wangaratta 1:250,000 scale NATMAP (SJ55-02) shows displacement of the Murray Valley Highway from its true position. The blue line is a GPS track showing the highway's true position, but the highway, railway and the Hume Freeway (red/yellow double line) have all been displaced for clarity. Compare this to the Landsat 7 ETM+ satellite image of the same area, where you cannot clearly distinguish between the three features. The relative position of the highway, the railway and the freeway have been maintained.

Generalisation is not a completely automatic process and some human judgement is required. Decisions are usually based upon the significance of the feature at the scale of the map being produced, how many other similar features there are nearby, and the purpose of the map itself.

One major impact of generalisation is when using maps with global positioning systems (GPS). When a GPS track is overlaid on a map, the track may not match the road as it is shown on the map because of the displacement described above. This isn't an error in the position of the road as such, but one of the consequences of trying to make a map clear and readable.

To make printing easier many features do not mask out other features. For example, if you have a close look at any of the new NATMAPs you would see that most rivers can be seen "underneath" or "on top of" the roads. The digital process used to manufacture the map images in NATMAP Raster can only show one layer in each pixel of the image, hence some features will be masked. The order in which the layering occurs is fixed, and in some maps may have produced some illogical results or effects that will not appear on the paper map. Significant illogical effects (such as canals covering roads) have been edited but may be incomplete.

The map images in Mapsheets appear tilted because they are georeferenced to the Map Grid of Australia (MGA).

Each map's boundaries are based on latitude and longitude, but these boundaries do not always correspond to MGA gridlines. In order to match the map image to MGA, the image has to be rotated and stretched. Note that the blue MGA gridlines on the map are orientated vertically and horizontally in the Viewer, whilst lines of latitude and longitude will be shown at an angle.

The map images in NATMAP Raster have been compressed. Images that are compressed are like files that have been "zipped" - information has been removed from the image using a particular technique or algorithm to reduce the file size.

Depending upon the compression technique, some information may be lost from the image altogether when it is compressed. This is called lossy compression. ECW, JPEG and MrSID are common lossy compression techniques. LZW is a lossless compression (i.e. information is not lost when an image is compressed); however, file sizes are not reduced as much.

The images in this product use ECW compression. This will mean that some features will lose some of their clarity; in particular, very thin lines such as tracks and watercourses may become blurry. Colours may also not be uniform within areas (e.g. forest areas shown as green on the paper map may, on the image, contain traces of other colours). These effects are called artefacts.

The resolution or cell size of an image also affects its clarity. Map images with a resolution of 150 dots per inch (dpi) will not be as clear as maps with 200 or 300dpi as there are less pixels in each image. As a result, text or other features in map images with lower resolutions will appear pixellated or blocky.

Other factors affecting image clarity include your monitor specifications, the software being used to view the map images (if not using the Raster Viewer), and the the zoom scale. If viewing in other software packages often there is an option to "zoom to raster resolution"; this zoom level will give the clearest view of the image. Zooming in too far will cause pixellation and artefacts will appear to be very significant; clarity is also reduced if zooming out too far. For best results, you should set your zoom to around the same level as if you were looking at the paper map version at the same viewing distance.

Whilst every effort has been made to minimise the number and extent of artefacts within each map image, users should be aware that artefacts exist as a result of fitting all of the NATMAP 1:250,000 scale maps onto 2 CDs at an affordable price. The map images in this product are not intended to be exact replicas of the paper map in terms of quality, but do contain the same information as shown on the paper version.

The number of artefacts may be minimised by exporting the map image to TIFF or GeoTIFF; however, these will produce very large file sizes and will not remove all artefacts, and cannot be viewed using the Raster Viewer. For more information, refer to the FAQ on the size of exported files.

For more information on compression techniques, refer to Image Compression in the ACRES product pages on the Geoscience Australia website.

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MAP IMAGE SPECIFICATIONS

File Naming Convention: all images in the 250K Sheet layer in the Mapsheets product are named to the corresponding six digit NATMAP 250K map number. Where a map does not have a NATMAP 250K map number, such as North West Tasmania, a number was created for that tile. Mosaic or individual map images are named according to scale; that is 250K.ecw, 1M.ecw, 5M.ecw, 20M.ecw. The Landsat 7 satellite image mosaic of Australia is named ls7_mosaic.ecw

Positional Accuracy: each identifiable coordinate pixel should be within 4 pixels of the calculated position. The production of maps involves cartographic generalisation of features which adds additional inaccuracies into the images. A full listing is below.

Note: the size of a pixel in metres for any of the Mosaic layers varies with the degree of latitude.

Coordinate System: Refer to the Coordinate Systems pages.

Currency: Refer to the map currency pages for the reliability dates for each standard map sheet area.

Legends:

1:250,000 scale [JPEG image, 71Kb]
Expanded 1:250,000 scale
1:1 million scale [JPEG image, 64Kb]
1:5 million scale [JPEG image, 26Kb]
Landsat Satellite Image Mosaic of Australia [JPEG image, 20Kb]
Gazetteer of Australia (used in Place Name Search)

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CD LAYOUT

Your NATMAP Raster product is organised on the CDs as follows:

Maps labelled * are part of the installation files, and become useable upon installation to your hard drive where they are visible in your chosen installation directory.

The maps (except for those labelled * in the table above) are stored in the Rasters folder on both CDs in both products. Within this folder is another folder which will be named with the appropriate layer name. See the table below.