Features

The essential information in VMAP0, and the information that is of interest to users of MapLink Pro Studio, is at the level of Feature. For each feature, the following information is of interest and is used to determine how entities of the given feature are handled within MapLink Pro Studio:

• The FACC. This is used as the basis for producing the MapLink Pro Feature Code.
• The Feature Name. This is used as the basis for producing the Label for the feature.
• Zero or more attributes.

Within VMAP0, a large number of attributes are defined for features, ranging from attributes that are essential to make use of if a good representation of the data is to be achieved, to attributes of no practical use or whose usefulness is compromised by partial and inaccurate data collection. Some attributes are specific to a given feature; others are widely used for many different features.

The catalogue of feature classes gives, for each coverage and feature class, a full list of attributes that are defined for each feature, with valid attribute values where relevant.

VMAP0 attributes are used in two ways within MapLink:

• Feature subclasses may be defined to a depth of two levels, using unique values of selected attributes as the basis for the definition of the subclasses. For example, the Road feature has attributes Median Category (MED) and Route Intended Use (RTT). Using feature subclassing, MapLink Pro Studio can create features such as:
• Road.With Median.Primary Route
• Road.Without Median.Primary Route
• Separate text features can be introduced, located at an appropriate position (depending upon whether the base feature is a point, line or area feature), using the value of the selected attribute as the text string. For example, features can be created to add elevation text to contour lines that have already been subclassed on the basis of their elevation:
• Contour Line (Land).152-Text
• Contour Line (Land).229-Text
• etc.

A standard definition of attributes to be used for feature subclassing and text feature creation is shipped with MapLink Pro Studio. This is intended to cover the needs of most VMAP0 users. In case an alternative approach is required, the file vpffield.ini (located in the MapLink Pro installation Config directory) may be edited accordingly:

• the switches SECONDARYn=att and TERTIARYn=att are used to define the two levels of feature subclassing;
• the switch TEXTn=att is used to define the text feature creation;

where n is the sequential number of the feature within the given coverage and att is the three-letter attribute code that has been selected for use.

Note that if the vpffield.ini file is modified from the standard configuration shipped with MapLink, it is probable that the standard VMAP0 section in the MapLink Pro Studio Feature Book will also have to be updated.