Coordinates and the coordinate system

What it does

This page covers four commands that work on one point at a time, and on the coordinate system that gives that point meaning.

The coordinate system is an acquisition chain, not a single setting. Whenever a GIS command needs to know which system the drawing is in, it walks, in this order: (1) the coordinate system recorded on the active alignment, (2) the value recorded in the dwg, (3) the Civil 3D system, if there is one and the drawing is set up to use it, (4) the last system used in the session, (5) the culture default (in the United Kingdom profile, BNG), and finally (6) the project setting, the session's temporary system and, again, the last used. The first that answers wins. CAPCAD_GEO_CRS is the form that records the value; CAPCAD_GEO_CRS_QUERY is the query that tells you what the chain returned.

The recorded value is a short string the converters understand: UTM-23 (zone 23 south, SIRGAS 2000), UTM-23-SAD69, UTM-23S / UTM-23N, a named system such as BNG or WGS-84, or EPSG:31983 for any EPSG code — and Undefined, which erases the setting. You never type it: you pick the system from the catalogue and the form records the right string for it.

The catalogue is the whole EPSG database. Pick by country or by category; see What actually converts below for the exact strings the converters resolve.

CAPCAD_GEO_POINT_IDENTIFY (CC) opens a modeless form with an input box that takes almost anything, and fills in at once: the station on the alignment, the projected pair (E,N / X,Y), the decimal latitude-longitude and the same in degrees-minutes-seconds. From there you copy it, insert a point in the drawing, or open the place on a map. The right-hand column searches an address on Google Places and uses the coordinate it finds as the input.

CAPCAD_GEO_LATLON (LL) is the form-free version: click a point, get lat,lon in a dialog and on the clipboard, click another, until you press Esc.

CAPCAD_GEO_CRS_QUERY opens nothing: it writes the resolved system on the command line (or Not set).

Workflow

1. Set the drawing's coordinate system: run CAPCAD_GEO_CRS. The list opens on your country — the one of the active country profile — so the systems in use where you work are already in front of you; type in Filter to narrow it, or switch Group to another country, to a region, or to <all>. Pick the system, choose whether it goes to the Project or the Alignment, and click Apply. With no active project the value goes to the dwg and a message says so.
2. Confirm with CAPCAD_GEO_CRS_QUERY: the resolved system appears on the command line.
3. Run CAPCAD_GEO_POINT_IDENTIFY (or type CC). The form opens modeless and the status line says whether an alignment is loaded.
4. Type or paste the coordinate into box 1 — or click Click point… (2) and take it from the drawing. Boxes 3 to 9 fill in on every keystroke.
5. Copy what you need (5, 8), insert a point in the drawing (6), or open the place in OpenStreetMap, Google Maps or Street View (10, 11, 12).
6. To sweep the drawing, use CAPCAD_GEO_LATLON (LL): each click shows and copies lat,lon; Esc ends.

The identification form

The form has a single state. The numbers below cover both forms on this page: 1 to 21 belong to CoordinateIdentifierForm, 22 to 31 to CoordSysForm.

CAPCAD_GEO_POINT_IDENTIFY freshly opened, with no input: the three map links and the insert-point button start disabled. The capture is of a Portuguese session — the numbering is the same in both editions, and the tables below give the English captions.

Besides the numbered controls, the form shows the headings Insert coordinates in any system and Address (type and press Enter), the hint You can paste Google Maps or OSM URLs directly, the label Detected: with the type recognised (UTM, LL or -), the labels Alignment km, UTM E,N / CAD X,Y, LAT-LONG DEC, LAT-LONG DMS and Coord system, and a grey status line at the foot of the left column.

Input (top left)

Readings (left column)

Maps (below the readings)

All three links (and button 6) stay disabled until there is a valid geographic coordinate: for a projected input that means the conversion has to have succeeded.

System and order (bottom)

Address (right column)

Footer

The coordinate-system form

CAPCAD_GEO_CRS in a Portuguese session, with the group on the country of the active profile.

Above the list the form shows the column headings System, Kind and EPSG, the frame title Record on, and, when a project and an alignment are loaded, a line reading Loaded: <project>\<alignment>. A second label shows the system currently in force.

What gets written stays readable by everything else. A system that has a CapCad short string is recorded as that string — UTM-23, UTM-23-SAD69, BNG, WGS-84 — and only a system without one is recorded as its EPSG code, EPSG:25832. So a drawing set up in an earlier version reads back exactly as it did, and one set to a system reached only by EPSG is understood by every command that asks for the drawing's system.

What actually converts

Every string the form records converts. Three shapes cover them all:

Three consequences worth stating plainly:

• The UTM- grammar covers South America; the rest of the world is reached by EPSG code, and the form does that for you. Those two zone bands are the SIRGAS 2000 and SAD 69 coverage. Everywhere else you pick the country's own system and the drawing is recorded as its code — ETRS89 / UTM 32N as EPSG:25832, the British grid as BNG — which converts exactly the same way.
• UTM-23 and UTM-23S are the same system. A zone written with no hemisphere is south and SIRGAS 2000; the -SAD69 suffix swaps the datum, and the two differ by tens of metres at the same point — the offset between SAD 69 and SIRGAS 2000. For the same reason a worldwide WGS 84 zone is recorded by its EPSG code rather than as UTM-nn: the two are different systems and the drawing keeps the one you picked.
• A drawing recorded as WGS-84 is in degrees. Nothing is projected: the reading you get back is the latitude and longitude themselves. To work in metres, record a projected system and read the LAT-LONG boxes for degrees.

The round trip closes: a projected pair converted to geographic and back returns the same eight decimal places, and the DMS reading agrees with them.

What the input box accepts

Every line below was passed through the box-1 parser itself.

Remembered between sessions

Neither form keeps any option between sessions. What persists is the recorded value: the coordinate system written to the project, the alignment or the dwg by CAPCAD_GEO_CRS, and the "last system used", which lives only as long as the CAD session and is updated by the GIS commands that import data.

Notes

• Comma decimals in the input box are read as separators. -23,55,-46,63 returns −23 and 55, accepted as valid, with no message. Use a dot decimal.
• Input with no comma, such as 600000E7419000N, is not accepted. Write the pair with a comma.
• Older datums are approximate. The transformations use Helmert parameters, without NTv2 grid files. Modern systems (SIRGAS 2000, WGS 84, ETRS 89) are exact; SAD 69 and other older datums land within 1 to 2 m. Enough to locate and visualise, not for geodetic use.
• CAPCAD_GEO_POINT_IDENTIFY › Localizar em eixo… opens the Station Navigator without its link to the drawing. On this path the station box, the zoom button and the two identify buttons are not available, and the alignment's station range does not appear. For the full form, run CAPCAD_ALIGNMENT_STATION_GOTO (shortcut KM) — see Station Navigator. The reverse path works: the Navigator's Localizar button closes the form and calls CAPCAD_GEO_POINT_IDENTIFY.
• The address search depends on the network and on a quota. It is a synchronous call to Google Places with the key that ships with CapCad; when the daily quota is exceeded, the service's own message appears on the status line.
• CAPCAD_GEO_CRS_QUERY opens no form and asks nothing. It only reports what the acquisition chain returned, with the default parameters (it does not try the last used, and it does not prompt).
• CAPCAD_GEO_LATLON is English-only. The point prompt (Pick a point (Esc to finish):) and the box that shows the result (Clicked / Coordinate system / Lat,Lon / (copied to clipboard)) have no other language. With no coordinate system set, the command writes "No coordinate system for this drawing — set one first (eixo / dwg / project)" and ends: it does not open CAPCAD_GEO_CRS for you, so run that first.
• Some prompts and status messages are Portuguese in an English session, including the point prompt of Click point…, the copy confirmation, the write confirmation and the two conversion-failure messages.
• Running CC or CAPCAD_GEO_CRS again with the form open does not open a second one. Both are modeless and single-instance: the command only brings the existing form to the front.