Cartography functionalities using CAC

Cartography using CAC

The task of digital cartography is to realise a meaningful presentation and a perfectly readable choice, for paper or electronic media distribution, of the GIS processed data. This is why an ergonomically graphic software with a wide range of special cartographic functions must be available to the mapmaker. As seen in the previous unit (GIS versus Cartographic Systems), many CAC systems exist. We will now present you the most needed tools for mapmaking, and also show you the advantages and disadvantages of cartography using CAC.

The most needed CAC tools for mapmaking

To depict the most needed CAC tools for mapmaking, we will have a look on the detailed functional demands for a new digital cartographic production system realised at the Federal Office of Topography in Switzerland:

• Input of analog and digital map data
• Visualisation of data on screen (WYSIWYG)
• Internal coordinate system
• Raster image manipulations
• Vector manipulations
• Editing of raster data (line art)
• Editing of vector data
• Hybrid processing of vector and raster data
• Text processing
• Processing of continuous tone data
• Bézier interpolation
• Data output

You can optionally download the following PDF to get some more information about the cartographic tools needed by Swisstopo for mapmaking: “ Hybrid "WYSIWYG" Techniques for updating the swiss topographic map series (390 Kb).

There is no sense in listing all the tools within a CAC here. We will just describe two of them in order to have a better understanding of the functionality differences between CAC and a GIS.

• WYSIWYG
  WYSIWYG is an acronym for “What You See (on your screen) Is What You Get” (in printout).
  A common problem in cartography is getting graphic displays and printed colours to match. Ideally, when creating a map on a graphic display, we would like to push a button and print a map having exactly the same colours. Unfortunately, this is generally not possible, because the colour production methods of graphic displays and printers are dissimilar. Fortunately, most of the CAC software have the potential to assist this process with a Colour Management System, which make an attempt to match the colours produced on graphic displays and printers. GIS does not currently support properly WYSIWYG colours functions.
• Transparency
  Transparency, which is an important tool for cartography, is presently unavailable in most of GIS, whereas most of CAC software includes it as a basic function.
  

Disadvantages of cartography using CAC

One of the main disadvantages of cartography using CAC is the loss of data attributes when importing GIS data. Indeed, when moving geographic data in a CAC software, shapes will be held whereas all the geographically critical aspects such as associated tables, coordinates, projections, scale and the resulting relationships among the elements will be lost. Therefore, you will not be able to edit attribute data, or undertake mathematical calculations on the attributes (for example, to calculate a percentage) of the geographical data within a CAC software. Some other common problems when importing GIS data in CAC software are:

• The GIS designated colours, fills and strokes, line weights, pattern styles for fills and strokes, fonts, etc. are quite often altered, or even lost.
• Labelling using attributes from the layers associated tables is not possible.
• The projection properties and parameters are lost.
• Etc.

Some specific software (like Avenza MAPublisher) fill the gap between GIS technology and CAC software. They allow to view, edit and update GIS data attribute/code, select objects and view their attributes in CAC software.