Relative Main Line layout algorithm properties

When the Relative Main Line schematic layout algorithm is chosen in the Layout Task drop-down list, clicking the Layout Algorithm Properties button on the Schematic Editor toolbar opens its associated properties dialog box with the tab as follows:

The parameter values are those either specified by default by Schematics or specifically set as the default for the schematic diagram template related to the active diagram using the Schematic Dataset Editor Layouts tab for this schematic diagram template.

About the lines definition's attributes and the root schematic node

The Relative Main Line layout algorithm works from attributes that allow the algorithm to identify the straight lines—that is, the main lines—and root schematic nodes from which those straight lines start.

Nota:

The attributes are held by either the schematic links or the GIS features associated with those links.

Root schematic nodes can be set using the Set Schematic Root tool to specify the starting points of the straight lines. If no root schematic node is set, the algorithm first searches nodes to find candidates to be the root node—that is, nodes connected to a single link that can be considered as the starting point for a straight line. Among those candidate nodes, the root node will be the one that starts the longest straight line.

Sugerencia:

Make sure the builder used to generate your diagrams works with the Initialize links vertices option checked, if you want the algorithm to process from the real direction of the lines.

The following figures show three sample schematic diagrams that are used to exemplify the Relative Main Line algorithm parameters in the next sections. They have been generated from a rail network:

• Diagram 1 represents a single track line with branches.
• Diagram 2 contains five tracks with their branches.
• Diagram 3 shows a single blue track which splits into two parts at the middle—a light blue portion and a dark portion—before merging further.

Nota:

In each sample diagram, the red schematic nodes are the root schematic nodes from which the algorithm works.

Lines definition section

The Lines definition section regroups the parameters that allow the algorithm to identify the schematic links that are part of straight lines from those of the branches. Those parameters are potentially related to three different attributes held by the schematic links or their associated GIS lines:

• A line definition attribute to identify the different straight lines (for example, a line identifier)
• A line type attribute to qualify each type of line (for example, primary line, secondary line, branch, and crossover)
• A priority attribute to set a priority level for lines that are split at a time

Sugerencia:

Because attributes are different from one dataset to another, there are no default values for the attribute parameters in the Lines definition section. However, if you want the Relative Main Line algorithm to perform from particular attributes by default, you can specify these default attribute names using the Schematic Dataset Editor Layouts tab for your schematic diagram templates.

Learn more about specifying schematic layout algorithms' default parameters

Line definition attribute

The Attribute name parameter provides the name of the attribute that will be used to identify the straight line for each schematic link. It's often an identifier whose value is supposed to be the same for all the links that compose a straight line—for example, Line 1, Line 2, and so on.

All connected links having the same value for that attribute will be considered as being part of a straight line; the other links will be considered as branches.

If the expected attribute is missing for a link, that link will be considered as part of a branch.

Figure 2 shows the result of the Relative Main Line algorithm layout on diagram 1 after it executes with a given line definition attribute, with the other parameters being the defaults.

In that case, specifying only the Attribute name parameter allows you to get a good layout; no other attributes are needed.

Precaución:

Attribute name is a mandatory parameter for the algorithm execution and must be the same (same name, same type) for all the schematic or GIS feature classes related to the links that are potentially part of the straight lines.

Line type attribute

The Line type attribute subsection regroups the parameters that allow you to qualify different types of lines. Those parameters are optional.

• Check Use a line type attribute if your schematic links or their associated GIS features hold such a line type attribute.
• Then specify the three following parameters:
  • Name field—the name of the line type attribute.
  • Main line value field (optional)—the attribute's characteristic value that identifies the main lines. When such a value exists, it must be the same for any link that composes the main lines whatever its schematic feature class is.
  • Excluded values field (optional)—the values that specify the line types you want to be excluded from the straight lines.
    Nota:

    This parameter may contain a unique value or a list of values. For a list of values, each value is separated by a semicolon (;) character.

Precaución:

For attributes related to fields with attribute domains, the expected values for the Main line value and Excluded values parameters are coded domain values.

Nota:

When excluded values are specified, none of the links with those attribute values will be considered as being part of any straight line. This parameter is especially useful to exclude links such as crossovers or ladders on rail networks.

Nota:

The Line type and Line definition attribute may be the same in some datasets. They can also be different; this depends on the dataset.

Figure 3.1 shows the result of the Relative Main Line layout algorithm on diagram 2 after it executes, while Attribute Name is the only specified parameter. In that case, the algorithm processes the brown crossovers as main lines.

Figure 3.2 shows the same diagram when using a line type attribute and specifying values to exclude the brown crossovers from the main lines.

Priority attribute

The Priority attribute subsection concerns parameters that allow you to specify priority levels for lines that are split at a time. Those parameters are optional.

• Check Use a priority attribute if your schematic links or their associated GIS features hold such a priority attribute.
• Then specify the two following parameters:
  • Name field—the name of the priority attribute.
  • Priority value field (optional)—the specific value of the attribute that identifies the line with the higher priority among split lines. When such a value exists, it must be the same for any link, whatever its schematic feature class is.

Precaución:

For attributes related to fields with attribute domains, the expected value for the Priority value parameter is a coded domain value.

Figure 4.1 shows the result obtained on diagram 3 when no priority attribute is specified for the Relative Main Line algorithm. In that case, when zooming in on the line features at the middle, we can see that the dark and light blue lines that come from the split, single blue track in the diagram could be better positioned. At the left, the dark line is aligned with the blue track it comes from; but, at the right, this is the light blue line that is aligned with the track.

Figure 4.2 shows the same diagram when using a line priority attribute and specifying the dark line with the highest priority. In that case, the algorithm aligns the straight blue track with the highest priority line—the dark one.

Direction section

The Direction options determine the direction of the lines:

• Choose From left to right to create lines starting from a root that will be positioned on the left and ending on the right (figures 5.1 and 5.2, below). This is the default option unless another option is specified on the diagram template related to the active diagram.
• Choose From top to bottom to create lines starting from a root that will be positioned at the top and ending at the bottom (figures 6.1 and 6.2, below):

Spacing section

The Spacing parameters determine how the spacing between nodes will be computed along the line direction and between branches perpendicularly to the direction.

• The Offset between branches parameter determines the spacing between two adjacent branches along the axis perpendicular to the direction of the lines. The unit for this parameter is the diagram unit.

  The figures below show the results of the Relative Main Line algorithm layout on diagram 1 and diagram 2 when Offset between branches = 40 (figures 7.1 and 7.2) and Offset between branches = 80 (figures 7.3 and 7.4):

• The Break point angle parameter specifies the angle that will be used to position the break point on the branches. It is a number between 30 and 90 degrees which is combined with the Offset between branches parameter value to compute this position. When the break point angle value is 90 degrees, each branch orthogonally displays.

  Figures 8.1 to 8.3 show the impact of the Relative Main Line algorithm layout for different break point angle values. Note that, depending on the values specified for the Offset between branches and Break point angle parameters, the algorithm may end with a direct line—no break point—for short branches. The orange branch in figure 8.2 and 8.3 and the pink one in figure 8.3 show such cases:

  The figures below show the results of the Relative Main Line algorithm layout on diagram 1 and diagram 2 when Break point angle = 90 degrees (figures 8.4 and 8.5) and Break point angle = 45 degrees (figures 8.6 and 8.7):

Initial distances section

The Initial distances options allow you to specify how the algorithm assesses the length of the schematic links. This length determines the positions of the nodes along the direction. The distances between the connected nodes along the direction are not equidistant; they are relative to each other and depend on the current link length and the length of the shortest link.

• Choose From link geometry for the algorithm to compute each link length from its current geometry (checked by default).
• Choose From link length attribute for the algorithm to compute each link length from a particular attribute. In that case, type the name of this attribute in the Attribute name field.
  Nota:

  When using this option, the attribute name is mandatory and the specified attribute must exist on all the link schematic features contained in the diagram or their associated GIS features.

Figure 9.1 shows the results of the Relative Main Line algorithm layout on diagram 2 when using the From link geometry option (default). Figure 9.2 shows the results obtained when using the From link length attribute option with a constant attribute value that causes each link in the diagram to be displayed with an equal length:

Compression section

The Compression parameters allow you to reduce the distances between adjacent groups of neighbor schematic nodes along the direction while trying to maintain relative positioning between these groups. Neighbor schematic nodes are nodes that are geographically close to each other without being directly connected. The compression parameters are optional; by default, the algorithm works without any compression. When compression is enabled, it executes as an extra step at the end of the algorithm process.

• Check Compress along the direction if you want to activate the compression.
• Specify the following two parameters:
  • Minimal distance field—the minimal distance that must be kept between two adjacent groups of neighbor schematic nodes.

    This minimal distance is also used to group neighbor nodes regarding their projection along the direction axis. Two nodes projected on this axis will belong to the same group when the distance between the two projected points is lower than this distance.

  • Ratio field—the compression ratio. This is a number between 0 and 1 that is applied to the length of any link after subtracting the minimal distance of its length. When Ratio is 1, the distance between each detected nodes group is equal to the minimal distance.

  Figure 10.1 shows the sample diagram 1 content laid out without any compression. If the compression was enabled, this extra step would start from the current layout and process as follows:

  With the specified D minimal distance, the algorithm will detect three node groups—the three orange squared groups. Then, the specified compression ratio will be used to reduce each L link length that separates two groups; this ratio being applied to the remaining (L-D) length.

Figures 10.2 to 10.5 show the results of the Relative Main Line algorithm layout on diagram 2 when using different compression ratios. When increasing the ratio, the distance between the node groups along the direction are more and more compressed. With Ratio = 1, the distance between the three node groups is equal and corresponds to the Minimal distance specified.

Restore Defaults button

Click the Restore Defaults button to reset all the Relative Main Line parameters to their default values. The restored values are those either specified by default by Schematics or specifically set as the default for the schematic diagram template related to the active diagram using the Schematic Dataset Editor Layouts tab for this schematic diagram template.