类别：线性参考

These transformers work with linear referencing data structures on FME features.有些变换器允许您创建和应用属性中保存的测量相关信息到FME特征的几何体。

FME如何支持线性参考

Linear referencing uses measures to associate attributes or events to locations or portions of a linear feature.

FME先前支持将措施写入地理数据库，SDE,以及通过包含逗号分隔的度量值列表的特殊属性生成的形状文件，corresponding to the coordinates of the feature.然而，in order to further support writing of measures,we still had to come up with a set of measures to populate.与从数据库表中提取度量值并在写出它们之前将它们组合成一个csv属性（就像某些应用程序那样）不同的是，有一个称为MeasureGenerator，它用一个逗号分隔的列表填充一个属性，其中列出了从行首到每个点的距离。然后可以将其发送到“shape\u measures”属性，并将其写出。

狙击变压器执行以下功能：

• Shortens the geometry of a line feature by snipping off a specified amount from the ends.从线路起点和终点截取的数量可以指定为地面单位的测量值或线路全长的百分比，starting from the first coordinate.

• Shortens the geometry of a line feature by snipping off vertices from the ends.原始直线上的顶点将形成结果直线的第一个和最后一个顶点，这些顶点被指定为数字索引，with "0" being the first vertex of the line.

此转换器可以将以“lrs”方式存储的数据转换为分段视图（如果您有一个“整体”几何图形表，and another event table that says where on a particular line things begin and end,you can do a join,and then a snip of some kind,and get out the segments).

• 这个LengthToPointCalculatorcalculates the length of a feature from its start until the closest spot to a point,and adds it as a new attribute.This can be used to create an LRS view from a segmented view,与ArcFactory（LineJoiner）和ReferenceFactory（FeatureMerge）巧妙结合时。