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NVG Interoperability: What Survives the Exchange
What exactly crosses the border when you exchange an overlay with another system through NVG — element by element, both ways. How to import and export is described on NVG; this page is the reference behind it.
In short
- map.army writes NVG 2.0.2 and reads NVG 2.0.0 and later.
- Symbols travel as MIL-STD-2525C codes. On import, symbols in any other scheme are left out.
- With Include MSS Data switched on (the default), a file exported from map.army and opened in map.army again comes back complete. Without it, the file is plain NVG and some map.army content is simplified or lost.
- Every conversion, replacement or omission is reported as a warning. Read them.
Symbols
| Direction | What happens |
|---|---|
| Export | Each symbol is written as 2525c: followed by its 15-character symbol code. A symbol that exists only in the Extended Work Mode is first turned into the nearest standard MIL-STD-2525C symbol, with the warning Extended symbol fallback to …. |
| Import | Only 2525c: codes are read. A symbol given as app6a:, 2525b:, app06d: or icon: is left out (NVG symbol ‘…’ is ignored). An unknown 2525c: code is replaced by the closest symbol in the standard if one exists, otherwise left out. A code that is not 15 characters long is skipped. |
Graphics, element by element
| In map.army | Written to NVG as | Read back from NVG |
|---|---|---|
| 1-point symbol | point with symbol, modifiers and label | yes |
| Corridor | corridor | yes |
| Line or area (polyline / polygon) | polyline / polygon | yes |
| Graphic with a fixed set of 2 to 4 points, wide arrow | multipoint | yes, if it carries a symbol |
| Fan | arcband | yes, if it carries a symbol |
| 1-point circle, generic circle | circle | yes |
| Generic ellipse | ellipse | yes |
| Generic rectangle | rect | yes |
| 1-point rectangle | polygon with four corners | yes |
| Generic Graphics: Bezier lines and Bezier areas | simplified: a rectangle around the shape, filled orange, with the warning Symbol generic fallback — the real shape only with Include MSS Data | the real shape only from the MSS data |
| Generic Graphics: Pins, Texts, symbol groups | not exported (MSS symbol is not supported) | — |
The other way round, an NVG file can contain elements map.army never writes:
| NVG element | On import |
|---|---|
arrow | read if it carries a 2525c: symbol, otherwise left out |
arc, orbit, text, composite, nested groups | left out (NVG element ‘…’ is ignored) |
| a line, area, circle or point without a symbol | becomes the matching Generic Graphic |
A top-level group in the file becomes one MilX layer, named after the group’s label. Objects outside any group go into one layer called NVG Layer.
Modifiers and styling
| Content | Without Include MSS Data | With Include MSS Data |
|---|---|---|
| Standard MIL-STD-2525C modifiers (echelon, unique designation, higher formation, date-time, altitude text, …) | kept, in the NVG modifiers attribute | kept |
| Affiliation, status, icon | kept, inside the symbol code | kept |
| map.army extensions — icon extensions, Swiss unit and installation modifiers, icon text (including emoji), custom colour and size, damage status | lost | kept |
| Free-format line and fill styling of Generic Graphics | partly translated into NVG styling; some styles change (for example dashed becomes dotted) | kept |
| Free-format text and text colour | lost | kept |
| Altitude | as modifier text only — NVG coordinates carry no height | as modifier text |
Include MSS Data writes the full map.army description of every symbol into the file as NVG Extended Data. A system that does not understand it simply ignores it, so leave it on unless the receiving side asks for a strictly minimal file.
Coordinates
- Positions are WGS84 longitude and latitude in decimal degrees, up to seven decimals.
- Distances — radii, corridor widths — are in metres, angles in degrees clockwise from north.
- On import, the coordinates are always read as WGS84. The coordinate-system choice in the import settings only decides which system the resulting MilX layer uses.
Metadata
The NVG metadata — title, confidentiality label, releasability — is exchanged when you switch it on, as described in NVG metadata. A plain Dublin Core summary (title, creator, classification) is always added to an export, so that systems that do not read the full security metadata still see the essentials.