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MapLink Pro Studio 11.1
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MapLink Pro Studio 11.1
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Optimisation allows groups of primitives of the same class (Polyline, Polygon etc.) and the same feature class to be grouped together into a single Batch entity. The Batch entity, due to its internal structure, is much faster to load than individually Vector loading its constituent primitives.
Vector Optimisation allows three levels of optimisation:
The default setting. Each individual entity is stored individually, and drawn individually.
Advantages: |
Allows selection and manipulation of individual entities. |
Disadvantages: |
Selection and manipulation of the Batch primitive is possible, but selection and manipulation of the constituent parts is not. Polygons with holes are not currently handled with vector optimisation, so polygon keyholing should be applied where necessary. |
Within a tile, primitives of the same class and feature class are batched together to form Batch primitives.
Advantages: |
Faster to load and render than individual entities. Faster transmission rate than Batch or individual primitives. Requires less memory and disk space to store than the equivalent individual entities or Batch primitives |
Disadvantages: |
Selection and manipulation of the Batch primitive is possible, but selection and manipulation of the constituent parts is not. Polygons with holes are not currently handled with vector optimisation, so polygon keyholing should be applied where necessary. |
Within a tile, primitives of the same class and feature class are batched together to form Batch primitives. The Batch primitive is then compressed to form a compressed Batch primitive.
Advantages: |
Faster to load and render than individual entities. Faster transmission rate than Batch or individual primitives. Requires less memory and disk space to store than the equivalent individual entities or Batch primitives. |
Disadvantages: |
Selection and manipulation of the Batch primitive is possible, but selection and manipulation of the constituent parts is not. Decompression (performed within MapLink Pro) is required when loaded. Polygons with holes are not currently handled with vector optimisation, so polygon keyholing should be applied where necessary. |
Optimisation for compression is controlled via the application of a scale factor. When the output map tiles are created, all coordinates (which are held in internal units (TMCs)) are divided by the scale factor before saving the tiles. The correct coordinate values are then reconstructed on loading the tiles by multiplying the saved values by the scale factor. MapLink will automatically optimise the storage of the scaled coordinates if possible to use an appropriate number of bits for each coordinate value. Depending upon the choice of scale factor, therefore, it may be possible to encode each coordinate as a pair of 16-bit or even 8-bit unsigned integers, compared with the pair of 32-bit signed integers that is otherwise used.
It is possible to gain significant additional compression using this technique, but it is also possible to degrade the quality of the map data in the tiles if the scale factor is wrongly chosen. In order to apply this technique successfully, you must understand the nature of your data in some detail. Good results can be obtained if the precision with which your map data is encoded exceeds the precision that you require in your map.
For example, your data may be encoded such that one input unit is equivalent to one centimetre at the true scale of the input coordinate system, whereas your requirements may be for maps that are accurate to approximately one metre. In this case, a scale factor of up to 100 could safely be applied. However, the use of a scale factor of 1000 would cause all coordinate values in the data to be truncated at a precision of 10 metres. The quality of the map data would therefore be degraded to an extent such that the map accuracy requirements could not be met.
Since the range of scale factors that can sensibly be applied to the data is dependent upon both the nature of the data and the requirements on its use, MapLink Pro does not impose a limit on the value of scale factor that can be applied. However, the scale factor can only sensibly be used in conjunction with a defined mapping between input coordinate system units and map units. For this reason, a warning message will appear if optimisation for compression is selected and no such mapping has been defined.
To apply Vector Optimisation to a Layer