How to read total station files: turning GSI, RW5, SDR and LandXML into coordinates
At the end of the day a total station often hands you angles and distances, not coordinates.
Field takeaways
- First work out whether the file holds raw observations or computed coordinates.
- Getting from raw observations to coordinates needs the instrument station and the orientation.
- In GSI every value starts with a code saying what it is; 81, 82 and 83 are coordinates.
- Coordinate order changes from file to file; LandXML writes the northing first.
- Keep the raw file; computed coordinates do not replace it.
Raw observations or coordinates?
A total station keeps two kinds of records. Raw observations are the horizontal angle, the vertical (zenith) angle, the slope distance and the instrument and target heights. Coordinates are the easting, northing and elevation computed from them. Many files carry both, some only one. If a file holds only raw observations, getting to coordinates needs the coordinates of the station the instrument stood on and the backsight orientation; without them the measurements may be perfect and the points still have nowhere to land.
Leica GSI: every value has a code
GSI lines are made of fixed-length pieces called words. Each word starts with a two-digit code saying what it is: 11 point number, 21 horizontal angle, 22 vertical angle, 31 slope distance, 81 easting, 82 northing, 83 elevation. The difference between GSI-8 and GSI-16 is whether the data field in each word holds 8 or 16 characters; long point names and large coordinates need GSI-16. Units are encoded inside the word too, and that is where you read whether angles are in gon or degrees.
Carlson RW5, Sokkia SDR, Nikon
RW5 files are comma-separated records, each line starting with an abbreviation that names its type: an instrument setup, a backsight, a sideshot or a stored coordinate. In Sokkia SDR files every record starts with a two-digit type; coordinate records and observation records are different types. Nikon files work in a similar way with record-type abbreviations. What they share is this: if the software reading the file does not recognise each line's type correctly, it can take an observation for a coordinate, or the other way round.
Coordinate order, and Y/X in Türkiye
Which value comes first changes from file to file. LandXML writes points as northing, easting, elevation; many CSV files give the easting first. Türkiye adds a habit of its own: the easting is called Y and the northing X, the reverse of X and Y in mathematics. In TM zones the easting has six digits and the northing seven; looking at that on the first point catches a file read in the wrong order straight away.
Before you process the file
Before processing a total station file, check the point count, the instrument stations, the angle unit and the coordinate system; the coordinate of a known point should give the expected value. Always keep the raw file. Computed coordinates do not replace it; when an orientation error turns up, the computation can only be redone from the raw observations.
Open your field data in the browser.
MapLab Survey Web opens KML/KMZ, DXF, Shapefile, GeoJSON, CSV and total-station files (GSI, RW5, SDR, Nikon, LandXML) in the browser. It never guesses the coordinate system silently; it asks you to confirm the datum and zone. Drawing, measuring, import and export work without signing in. Interface in Turkish and English.
Frequently asked questions
What is the difference between GSI-8 and GSI-16?
The length of the data field in each word: 8 or 16 characters. Long point names and large coordinate values need GSI-16.
The file has no coordinates, only angles and distances. What do I do?
Coordinates are computed from the coordinates of the instrument station and the backsight. If the file does not contain them, get them from the field book or the crew who did the survey.
The points land far away, in another country. Why?
Most likely easting and northing were read the wrong way round. In Türkiye's TM zones the easting has six digits and the northing seven; use that to fix the order.
Which total station files does MapLab Survey Web open?
Leica GSI-8/16, Carlson RW5, Sokkia SDR, Nikon and LandXML. It never guesses the coordinate system silently; it asks you to confirm ITRF96 or ED50 and the zone.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: GNSS or total station? · Points from azimuth · CSV coordinate list · MapLab Survey