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9 3 1 1 6 6 2 1 8 2 4 4 9 Custom mapping The Department of Environment and Resource Management (DERM) can produce customer-defined maps for a particular area, which include information from departmental spatial datasets such as: • aerial photography • satellite imagery • property boundaries • topography (contours and drainage). Customers can request information from an individual dataset or a combination of data sets. However, this can be limited by the type of data available across the State. Also, customers can nominate the size and scale of the map, which is supplied in hardcopy and as a laminated paper plot. The scale may be limited to the quality of the available image. Aerial photography Aerial photographs are classified as either unrectified or rectified images. An unrectified image is an air photograph that still contains distortion caused by the undulating ground terrain and aircraft motion. A rectified image, or orthophoto, is where the distortion has been removed by a combination of ground control and computer software. As it is not possible to measure distance or area accurately on an unrectified image, data such as property boundaries and contours can be overlaid only on rectified images. When two or more images are necessary to cover a site, the customer should consider requesting a satellite image map, as it is a more cost-effective alternative. Property boundaries Custom maps use data from DERM’s Digital Cadastral Database. This database holds information on property boundaries, which is generally no more than a month old. DERM is currently upgrading the database to improve the accuracy of cadastral information available across the State. (An accuracy statement is included on the title strip of each custom map.) Topography Depending on available topographic or orthophoto mapping of the site, topographic data ranges from 1–20 metre contour intervals. (An accuracy statement is included on the title strip of each custom map.) Other components Map grid Customers can request inclusion of a map grid. The grid displays eastings and northings coordinates from the Map Grid of Australia 1994 (MGA94)—a standard Universal Transverse Mercator projection The one used is based on the GDA94. For all practical purposes this is the same as WGS84—used in global positioning systems. Grid intervals are usually governed by the scale of the custom map. A grid cannot be fitted to a custom map made on unrectified imagery. Title strip All custom maps include a title strip with: • a scale bar • a north point • information about the data content • accuracy statements • departmental contact details • a map reference number. When the site has a particular name (e.g. a rural property name), customers can ask for it to be displayed prominently in the title strip. Map scale and size Customers can request maps of a nominated scale or size. Maximums are limited by: • paper size—the maximum available is 900 x 1200 millimetres • pixel size of aerial photographic images—this determines the maximum enlargement possible. Digital data A custom map prepared using rectified imagery, property boundaries and topography can be supplied as a restricted PDF. This is locked with a password (to prevent data extraction or editing) but can be printed. The rectified imagery, property boundaries and topography can all be purchased individually in digital format by emailing <geoinfo@derm.qld.gov.au>. An air photographic mosaic can only be supplied as a digital image file. Digital format includes imagery only (without overlay showing property boundary). File formats are available to suit most software packages. All digital data is sold under licence. 2 Cost The main cost component of custom-mapping is labour, which is charged at an hourly rate, regardless of map size. There are also charges for the data content, paper, laminating and postage, with the average price being $250–350. These prices are a guide only. DERM assesses each request individually and gives the customer a firm quotation before undertaking any work. Customers will receive a quotation describing: • data availability, age and accuracy • suggested scale and map size • cost and methods of payment • timeframe for completing the map. Enquiring about a custom map Before a custom map can be produced, customers must describe the area to be mapped by supplying any of the following: • Lot on Plan numbers of all lots to be mapped (preferred option) • a map with a rectangle drawn on it defining the extent of the area • latitude and longitude or grid coordinates of the extent (including the datum). Customers should also provide details of their mapping requirements. For example: • show aerial photography, property boundaries and contours • use maximum scale on A0 size paper • supply two copies of the map, one laminated. Customers should email the information to <geoinfo@derm.qld.gov.au> or contact the department on (07) 3896 3019. Further information For more information on custom mapping visit the DERM website <www.derm.qld.gov.au>. Figure 1: Example of a typical custom map showing an aerial photograph, which contains property boundaries depicted in yellow and topography as white contours. April 2009 L110
