Feature lines have two types of points that define their geometry:
PIs and
elevation points. A PI is represented by a square grip and can be modified in all three dimensions. An elevation point is represented by a circle grip and has a more constrained editing behavior.
Figure 17.3 shows both types of grips on the same feature line. The elevation of an elevation point can be edited, but its location in plan view must slide along the feature line geometry determined by the PIs. This constrained behavior is actually quite handy because you can create many elevation points on a simple plan view shape such as a rectangle.
![Two crossing feature lines that occupy the same site Two crossing feature lines that occupy the same site](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTw73RWr2n42_Qk6mdqWa0Y6dHq5TD27Q_7AsEsKGDumtDd-D3I4rsOZZJoXNQt-hv2Sk3OyHS09Y_TN9a7RrWN6cYnu-OkXHJxxhfY3GMZMKmmxKN1aHcmnO8c0i3hYYTDv_hSwc9DfRA/s400/A-plan-view-of-PI-and-elevation-point-grips-on-a-feature-line.jpg) |
Figure 17.3 A plan view of PI and elevation point grips on a feature line. |