Skip to main content

Segments and sides

A facility is rarely symmetric to the criteria engine. A door faces one direction; a thick rear wall faces another; the criteria treat them differently. Sides and segments are how Siter captures that asymmetry — sides on the calculator, sides plus segments once you cross into the GIS.

In day-to-day calculator work, sides and segments are interchangeable: a named face of the facility you enter data against. Once geometry enters the picture in Siter, sides and segments split into two related-but-distinct concepts.

Learning objectives

By the end of this lesson you should be able to:

  • Distinguish a side (a named face, present on both calculator and map) from a segment (an angular slice projected on the map, GIS-only)
  • Predict what the calculator shows for a segmented vs unsegmented type code
  • Recognize the failure mode when a multi-face feature has no front assigned

Sides: the named faces of a facility​

Each criteria set defines, per type code, the sides a facility has. The calculator presents one input section per side, and the user enters that side's data — every side stands on its own.

A few DCMA examples:

Type code groupSides
ECM (ECM7, ECM3, ECMU)front, right, rear, left
Door-bearing facilitiesdoor, other
Unsegmented (e.g., AGM, IHB)a single Perimeter

When a type code is unsegmented, the calculator still shows one side input, just labeled Perimeter. The side concept never disappears — there's just nothing to subdivide.

Switching the type code mid-analysis swaps the side set: pick an ECM and you get four inputs; switch to AGM and you get a single Perimeter input. The previous side data is dropped if it no longer applies, and any required-but-unset values fall back to defaults — the same reload behavior as attributes.

Segments: angular slices around a facility (GIS only)​

In Siter, each side has a corresponding angular sweep projected around the facility on the map. That projection is the segment. Segments are how the GIS decides which side an ES falls into for a given PES → ES pair: the engine reads the bearing from the PES to the ES, finds the segment that bearing lands in, and uses that side's data for the analysis.

The calculator has no geometry, so segments are not visible there — only the named sides matter. Segments only become a distinct concept once a feature is on the map and the engine has to decide which side faces a particular ES.

The sweeps are defined by the criteria — the same segment-code data that names the sides also encodes the angular widths each one occupies. For an ECM under DCMA, for example, front covers a wider sweep than left or right, because the criteria treat the front (where the door usually sits) as having broader influence than the side walls.

Facility fronts: the orienting reference​

The segments need a reference face to swing the sweeps from. That reference is the facility's front. Once you assign the front, the engine can place every other segment relative to it.

  • Multi-face type codes (ECM, DOOR-style) — require an assigned front. A feature without a front lands in Requires Analysis and is excluded from results until a front is set.
  • Single-face type codes (UNSEGMENTED — AGM, IHB, PTR, etc.) — do not need a front. There is nothing to orient when the entire perimeter is one side.

Set fronts on individual features via the feature dashboard, or in bulk via Facility fronts.

warning

A missing front is silent in the calculator (which has no geometry) but loud in Siter — the feature simply does not analyze. Whenever an ECM disappears from project results, check the front before anything else.

Try it​

In the calculator:

  1. Pick an ECM7 type code and observe the four side inputs (front, right, rear, left)
  2. Switch the type code to AGM and observe the single Perimeter input
  3. Switch back to ECM7 — the four side inputs return, with previously entered values dropped

In Siter:

  1. Place an ECM on the map without assigning a front and run analysis
  2. Confirm the feature appears in Requires Analysis and produces no arcs
  3. Assign a front via the feature dashboard and re-run; the segment wedges now project from the facility and arcs appear per side