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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
  • Read a facility's default faces on the Segments tab and predict which faces a custom face replaces
  • Recognize when an older facility needs Regenerate Faces

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.

Each type code belongs to a segmentation scheme, and the scheme's sides come from the criteria:

SchemeType codesSides
ECMECM7, ECM3, ECMU (and FRM in DCMA and DESR 2024)front, right, rear, left
DOORNATO AGMRCWRdoor, other
BNDBND (boundary)a single Perimeter
Unsegmentedmost other type codes (e.g., AGM, IHB)a single Perimeter (perimeter in NATO)

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.

Faces: what the engine actually analyzes​

On the map, Siter turns each side into a face — the edge (or perimeter) of the facility's shape that stands for that side, with its search zone. Faces are listed on the facility's Segments tab.

Default faces are named after the criteria's sides. An ECM has four default faces named front, right, rear, and left; a NATO AGMRCWR has door and other; a perimeter facility has one face named after the criteria's perimeter side (Perimeter in DCMA and DESR 2024). Submittal forms print the same side names.

A few points that changed in v0.31 and come up in class:

  • NATO AGMRCWR faces are door and other (they were front and rear). The door face uses the criteria's 45° door angle (it was 60°), so those facilities' crowns and search zones change the next time their faces are rebuilt, and the door face gets the AGMRCD analysis code. Existing door facilities were converted on upgrade, keeping their results
  • Other facilities are renamed the first time they are saved after the upgrade. The rename alone doesn't count as an edit
  • Holes count. A facility with holes is measured to its nearest edge, holes included. A BND face includes the edges of every hole, so a site inside a hole is measured to the hole's edge, not the far outer edge
  • Changing to a type code with different sides (for example ECM to BND) resets the Analyze choice and Barricaded flag of that criteria's default faces — a side of the old type code is not the same side of the new one

Custom faces replace a side​

When the default faces don't fit the structure, a custom face (an alpha feature) can stand in for a side. Each custom face is tied to one criteria side by its Analyze As choice, and analysis treats it as that side:

  • On a four-sided (ECM) or door facility, a Custom Segment or Custom Perimeter replaces that side's default face. The other sides keep their default faces
  • On a perimeter facility, a Custom Segment is carved out of the default perimeter, and the default face is analyzed as the rest of the outline. Forms print it with "(remainder)", for example "Perimeter (remainder)"
  • A Custom Point adds an analysis point and replaces nothing

The Segments tab's Analyze column shows the result for each face, with hints such as "Replaced by Loading Dock" or "Replaces front". Each face can be set to always or never be analyzed. A side left with no analyzed face is flagged "Not analyzed — no face covers this side", and its submittal forms print a Sides not analyzed row. See Feature shapes → Custom analysis segments.

Older facilities and Regenerate Faces​

Facilities whose default faces don't match their criteria's sides — for example a single perimeter face on a four-sided ECM — are not converted automatically. Their submittal forms print Sides not analyzed. Fix them with Regenerate Faces, either on one facility's Segments tab (then save) or for the whole project from Analysis > Regenerate Faces, and re-run the analysis. Custom faces, Analyze choices, and barricade flags are kept.

Path facilities​

A path facility (a road drawn as a centerline and width) is an ordinary polygon since v0.32. Its faces follow its type code like any other facility's, it can take a front and custom segments, and a BND face includes the edges of any infields.

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. — and BND) — 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
  4. Open the ECM's Segments tab and confirm the four default faces are named front, right, rear, and left
  5. In edit mode, add a Custom Perimeter with Analyze As set to the ECM's rear side. Confirm the rear default face's hint reads "Replaced by" and the custom face's name, then click Discard changes