Map Measurement and Zeroing Checklist

Build a Clean Input Sheet

Record the map or mission name, gun coordinate, observer coordinates, target reports, distance unit, and angular unit in separate fields. Write the origin beside every bearing and range. Keep coordinates in one axis order throughout the sheet. If the map labels are coarse, preserve the best available decimal estimate instead of rounding every point to a grid corner.

A calculator can solve exactly the information it receives, but it cannot detect that east and north were swapped on the original note. The purpose of the input sheet is to make each assumption visible before it reaches the tool.

Coordinate Checklist

• Use one north-up coordinate system for gun, observer, and target points.
• Confirm which value is horizontal and which is vertical.
• Record the gun position before measuring anything else.
• Do not move the origin to make the arithmetic simpler.
• Keep decimal precision through the geometry stage.
• Check that every point falls inside the expected map area.

When a target coordinate is already known, use the coordinate difference to sanity-check direction. A target with a larger east coordinate should appear to the right of the gun on a north-up plot; a larger north coordinate should appear above it.

Bearing Checklist

IRON NEST HQ geometry uses north as 0 degrees and bearings increase clockwise: east is 90, south is 180, and west is 270. This differs from the conventional mathematical angle that starts from the positive horizontal axis and increases counterclockwise. Do not convert by intuition. Enter the displayed north-clockwise bearing directly when it already follows that convention.

If a report uses mils, identify whether it uses a 6400-mil or 6000-mil circle. Open the Mils to Degrees Converter, select the circle, and keep the original value on the input sheet beside the conversion. That allows you to catch a wrong convention later without reconstructing the report.

Distance and Scale Checklist

Use one distance unit for every point in the same calculation. Two circles with radii in different units cannot produce a meaningful intersection. Do not judge a printed range by the visual length of the line alone; the tactical plot may auto-fit distant points. Read the numeric result and scale state.

For a direct bearing-and-range report, the entered range belongs to the report vector. For a relay, each leg has its own range, while the tool computes a new final range from gun to target. For triangulation, each reported distance stays attached to its own station. Label these roles explicitly.

Zeroing Workflow

1. Freeze the gun coordinate and map unit.
2. Choose Direct, Relay, or Triangulation from the report structure.
3. Enter the values without early rounding.
4. Inspect target direction, coordinate, candidate count, and final range.
5. Copy the complete geometry result before opening Ballistics.
6. Select a community-reference charge and elevation for the final range.
7. Verify the load in the current game build.
8. After impact, recheck the original sheet before applying one correction.

This order protects geometry from being silently changed while you tune a firing reference. If the shot misses, you still have the exact first solution to compare.

Worked Measurement Example

Suppose a made-up training grid places the gun at (4.2, 3.5) and the target report gives a bearing of 90 degrees with a range of 6 units. The target should lie directly east at approximately (10.2, 3.5). If the plot instead moves north, the bearing convention was interpreted incorrectly. If the target lands at (10, 3), precision was lost before projection. This simple cardinal-direction check is useful before trusting a more complicated oblique vector.

Open Direct mode and reproduce a simple north, east, south, or west case whenever you are unsure about axes or bearing direction.

When Triangulation Looks Wrong

For bearing–bearing, confirm that both rays point toward the expected sector rather than away from it. For bearing–distance, verify that the distance circle is centered on the correct station. For distance–distance, compare the station separation with the two radii: circles that are too far apart or one entirely inside the other have no intersection. Open the Triangulation Calculator and inspect all candidates instead of editing measurements until one preferred point appears.

Common Zeroing Mistakes

• Changing charge and geometry at the same time after a miss.
• Correcting from the visual plot rather than the printed output.
• Rounding observer positions before intersecting constraints.
• Converting mils with the wrong circle convention.
• Measuring the final range from the spotter instead of the gun.
• Keeping an old target coordinate after changing an input.

Final Input Card

Your clean card should contain the gun coordinate, report mode, all observer coordinates, each measurement with its origin, units, selected candidate, final target coordinate, firing bearing, final range, and converted angular value if used. Keep charge and elevation in a separate load block. That separation makes troubleshooting faster and prevents a community-reference value from being mistaken for a geometry result.

Continue with the First Firing Solution Guide, or use Why Your Shot Missed when you already have an incorrect impact to diagnose.