3.1. GSI Editor

The GSI Editor is a tab-based tool for viewing, editing, and converting Leica GSI survey data files. It provides a decoded, human-readable grid view of the binary-style GSI format, making it straightforward to inspect and modify field measurements before further processing.

3.1.1. Overview 

GSI Editor main window showing decoded measurement data in a grid

The GSI Editor supports:

Opening multiple GSI files simultaneously in separate tabs
Viewing decoded GSI data in a 24-column grid covering all standard Word Index codes (WI 11–88)
Editing field values with real-time validation (angle range 0–400 gon, distance >= 0, point name length limits)
Saving and exporting to GSI8, GSI16, XLSX, and CSV formats with automatic file extension
Importing measurement data from CSV or XLSX spreadsheets via a 3-step column mapping wizard
Visual row coloring: station setup lines (light blue), set-of-angles result lines (light gray)
Invalid cells highlighted in red for quick identification of data problems
Auto-detection of GSI8 vs GSI16 format on file open

3.1.1.1. Leica GSI Format Reference 

3.1.2. Overview 

GSI (GEO Serial Interface) is an ASCII text format used by Leica total stations (TPS series) and digital levels (DNA series). Each line in a GSI file represents one measurement or station record, composed of space-separated data words.

Two format variants exist:

GSI8 – 8-character data portion (15 characters per word total)
GSI16 – 16-character data portion (23 characters per word total)

The first word on each line starts with an asterisk (*) to mark the beginning of a new record.

*110001+0000000000000101 21.022+0000000009521400 22.022+0000000009876300 31..00+0000000000125340
*110002+0000000000000102 21.022+0000000012345600 22.022+0000000010012500 31..00+0000000000098760

3.1.3. Word Structure 

Each data word in GSI16 format is exactly 23 characters long. In GSI8 format, each word is 15 characters long. The structure is identical; only the data portion length differs.

GSI16 Word Structure (23 characters)
Position	Name	Description
1–2	Word Index (WI)	Two-digit code identifying the data type (see Word Index Table below)
3	Auto-index info	`0` = auto-increment OFF, `1` = auto-increment OPERATING
4	Input mode	`0` = measured by instrument, `1` = entered via keyboard, `2` = Hz-corrected value
5	Additional info	Instrument-specific additional information
6	Units indicator	Specifies the measurement unit and decimal precision (see Units table)
7	Sign	`+` or `-`
8–23	Data	16-character zero-padded numeric value (8 characters in GSI8)

Note

The leading asterisk (*) that marks the first word of each line is not counted in the 23-character word length. The parser strips it before decoding.

3.1.4. Units Indicator 

Position 6 of each data word encodes the measurement unit and implied decimal precision:

Units Indicator Codes
Code	Unit	Decimals	Description
0	Meters (mm)	3	Millimeter resolution
1	US Feet (1/1000 ft)	3	Thousandths of a foot
2	Gradians (gon)	5	400 gon = full circle
3	Degrees (decimal)	5	360 degrees decimal
6	Meters (1/10 mm)	4	Sub-millimeter resolution
8	Meters (1/100 mm)	5	High-precision distance

3.1.5. Word Index Table 

The Word Index (WI) is the two-digit code at positions 1–2 of each data word. It identifies what type of data the word contains.

Complete Word Index Reference
WI	Name	Description
11	Point Number	Target point name or identifier
12	Serial Number	Instrument serial number
13	Instrument Type	Instrument model identifier
16	Station Point Number	Station (instrument) point name
17	Date	Date stamp of measurement
18	Time format 1	Year, seconds, milliseconds
19	Time format 2	Month, day, hour, minute
21	Hz Angle	Horizontal circle reading (gradians)
22	Vz Angle	Vertical/zenith angle (gradians)
25	Hz Circle Diff	Horizontal circle difference
31	Slope Distance	Slope distance (meters)
32	Horiz Distance	Horizontal distance (meters)
33	Height Diff	Height difference (meters)
41	Code Number	Code block number
42–49	Info 1–8	General information fields
51	PPM/Constants	Parts per million + prism constant
52	Measurements	Number of measurements + standard deviation
53	Deviation	Deviation value (sub-codes: 531 = atmospheric correction/pressure, 538 = coefficient of refraction)
58	Signal Strength	EDM signal strength / prism constant
59	Prism Constant	Reflector constant (1/10 mm) / PPM
71	Point Code	Feature code
72–79	Attributes 1–8	User-defined attribute fields
81	Target Easting	E coordinate of target point
82	Target Northing	N coordinate of target point
83	Target Elevation	H (height) of target point
84	Station Easting	E coordinate of instrument station
85	Station Northing	N coordinate of instrument station
86	Station Elevation	H (height) of instrument station
87	Reflector Height	Prism/target height above ground mark
88	Instrument Height	Instrument height above ground mark

3.1.6. Special Record Types 

Station setup records

A line that contains station coordinate words (WI 84, 85, 86) but does not contain horizontal or vertical angle words (WI 21, 22) is interpreted as a station setup record. This marks the beginning of a new instrument station. In the grid, station setup rows are highlighted with a light blue background.

Set-of-angles (SOA) result lines

Lines starting with WI 41 that contain names such as HZ-RESLT, HZ-MEAN0, or HZ-DIFF0 are Leica’s internal averaging results from set-of-angles measurements. These lines are displayed in the grid with a light gray background and are read-only (not editable).

Face I / Face II detection

The editor determines the telescope face from the vertical angle (WI 22):

Face I: Vz < 200 gon
Face II: Vz >= 200 gon

3.1.6.1. Opening the GSI Editor 

The GSI Editor is accessed from the application sidebar:

In the main SurveyTools window, expand the Tools section in the left sidebar.
Click GSI Editor.

The editor opens with an empty grid and two tabs at the top: Data (the measurement grid) and Options (format and unit settings).

3.1.6.2. Opening GSI Files 

To load a GSI file into the editor:

Click the Open button in the toolbar at the top of the editor.
In the file dialog, select one or more .gsi files. The dialog accepts both GSI8 and GSI16 files.
Click Open. The file contents are decoded and displayed in the grid.

The editor automatically detects whether each file uses GSI8 or GSI16 encoding based on the word length (15 or 23 characters per word). The detected format is shown in the Options tab under the GSI Format radio group.

Note

You can open multiple GSI files. Each file loads into the same data grid. Use the Options tab to verify that the detected format matches your expectations.

3.1.6.3. Understanding the Grid 

The data grid presents decoded GSI data in a spreadsheet-like view with 22 columns. Each row corresponds to one line (record) in the original GSI file.

The columns, listed in display order, are:

Grid Columns
Column Header	WI Code	Data Type	Contents
Point Name	11	Text	Target point identifier (leading zeros stripped)
Station Point Number	16	Text	Station point name
Horizontal Angle	21	Float	Horizontal circle reading (gon)
Vertical Angle	22	Float	Zenith/vertical angle (gon)
Slope Distance	31	Float	Slope distance (m)
Horizontal Distance	32	Float	Horizontal distance (m)
Height Difference	33	Float	Height difference (m)
Atmos.Correction: pressure	531	Float	Atmospheric correction (pressure)
Coefficient refraction	538	Float	Refraction coefficient
Prism Constant	58	Float	EDM signal strength / prism constant
PPM	59	Float	Parts per million correction
X (Easting)	81	Float	Target easting coordinate
Y (Northing)	82	Float	Target northing coordinate
Z (Elevation)	83	Float	Target elevation
Station Easting	84	Float	Station easting coordinate
Station Northing	85	Float	Station northing coordinate
Station Height	86	Float	Station elevation
Reflector Height	87	Float	Target/prism height above mark
Instrument Height	88	Float	Instrument height above mark
Date	17	Text	Measurement date
Time	19	Text	Measurement time

The footer row at the bottom of each column displays the GSI word index code for reference.

3.1.6.3.1. Grid Features

The grid supports several built-in operations via keyboard shortcuts:

Keyboard Shortcuts
Shortcut	Action
`Ctrl`+`F`	Open the Find dialog to search within the grid
`Ctrl`+`G`	Show/hide column visibility dialog
`Ctrl`+`T`	Open the filter dialog
`Ctrl`+`S`	Open the sort dialog
`Ctrl`+`A`	Select all rows
`Ctrl`+`K`	Optimize (auto-fit) column widths
`Ctrl`+`C`	Copy the value of the current cell

3.1.6.4. Editing Values 

The grid supports direct in-cell editing. To modify a value:

Click on the cell you want to edit. The cell enters edit mode.
Type the new value.
Press Enter or Tab to confirm, or Escape to cancel.

Pressing Tab advances the cursor to the next column (left to right, then down to the next row).

3.1.6.4.1. Validation Rules

The editor validates input according to the data type:

Validation Rules
Field Type	Rule
Horizontal Angle (WI 21)	Must be a number in the range 0 to 400 gon
Vertical Angle (WI 22)	Must be a number in the range 0 to 400 gon
Distances (WI 31, 32, 33)	Must be a non-negative number (>= 0)
Point Names (WI 11, 16)	Text; maximum length depends on format (8 chars for GSI8, 16 chars for GSI16)
Coordinates (WI 81–88)	Must be a valid floating-point number

Warning

Cells that fail validation are highlighted with a red background. You must correct invalid values before saving or exporting the file. The editor will not prevent you from navigating away from an invalid cell, but the red highlight serves as a persistent reminder.

3.1.6.5. Row Colors 

The grid uses background colors to distinguish different record types at a glance:

Row Color Legend
Color	Meaning
Light blue	Station setup record. This row defines a new instrument station (contains WI 84/85/86 but no WI 21/22).
Light gray	Set-of-angles (SOA) result. Leica internal averaging line (e.g., `HZ-RESLT`, `HZ-MEAN0`, `HZ-DIFF0`). These rows are read-only.
White	Normal measurement observation. Fully editable.
Red cell	Individual cell with an invalid value that fails validation.

3.1.6.6. Saving and Exporting 

To save or export the current data:

Click the Export button in the toolbar.
In the Save dialog, choose the output location and filename.
Select the desired format from the file type dropdown:
- GSI16 (.gsi) – Leica GSI-16 format
- GSI8 (.gsi) – Leica GSI-8 format
- XLSX (.xlsx) – Microsoft Excel spreadsheet
- CSV (.csv) – Comma-separated values
Click Save.

The file extension is set automatically based on the selected format.

Note

When exporting to XLSX or CSV, all columns in the grid are included. Column headers are written as the first row. This is useful for creating reports or importing the data into other software.

3.1.6.7. Importing from a Spreadsheet 

The GSI Editor can import measurement data from CSV or XLSX files and convert them to GSI format using a 3-step wizard.

3.1.6.7.1. Step 1: File Selection

Launch the import wizard from the toolbar.
Browse to and select the source CSV or XLSX file.
A preview of the first few rows is displayed so you can verify the file was read correctly.

3.1.6.7.2. Step 2: Column Mapping

Map each column in the source spreadsheet to the corresponding GSI word index:

Use the dropdown menus to assign each source column to a GSI field (Point Name, Hz Angle, Vz Angle, Slope Distance, etc.).
Columns that do not correspond to a GSI field can be left unmapped (skipped).

3.1.6.7.3. Step 3: Summary and Import

Review the mapping summary showing which source columns map to which GSI fields.
Confirm the import. The data is loaded into the grid.
You can then edit the imported data and export it in any supported format.

3.1.6.8. Working with Multiple Files 

The editor supports opening multiple files into the same data grid. Each call to Open appends the new file’s records to the existing grid contents.

Note

To start with a clean grid, close and reopen the GSI Editor before loading a new file.

3.1.6.9. Typical Workflows 

3.1.6.9.1. Convert GSI to Excel

Open the GSI Editor from Tools > GSI Editor.
Click Open and select your .gsi file.
Verify the decoded data in the grid. Check the Options tab to confirm the correct format and units were detected.
Click Export, choose XLSX as the format, and save.

3.1.6.9.2. Edit Point Names

Open the GSI file in the editor.
Navigate to the Point Name column (first column).
Click on the cell for the point you want to rename and type the new name.
Repeat for additional points as needed.
Click Export and save as GSI16 or GSI8 to write the updated file.

3.1.6.9.3. Convert GSI8 to GSI16

Open a GSI8 file. The editor auto-detects the format.
Go to the Options tab and select GSI 16.
Click Export and save. The output file uses 16-character data words.

3.1.6.9.4. Import CSV and Save as GSI

Open the GSI Editor.
Launch the import wizard and select your CSV file.
Map the CSV columns to GSI fields (e.g., column A = Point Name, column B = Hz Angle).
Confirm the import. The data appears in the grid.
Go to the Options tab and select the desired GSI format (GSI8 or GSI16) and units.
Click Export and save as .gsi.

3.1.6.9.5. Inspect Station Setups

Open a GSI file containing multiple station setups.
Scan the grid for rows highlighted in light blue – these are station setup records.
Check the Station Easting, Station Northing, and Station Height columns (WI 84, 85, 86) to verify station coordinates.
The Instrument Height column (WI 88) shows the height of instrument above the ground mark for each station.

3.1.6.9.6. Verify Face I / Face II Observations

Open the GSI file and examine the Vertical Angle column (WI 22).
Values less than 200 gon indicate Face I observations.
Values of 200 gon or greater indicate Face II observations.
Use this to confirm that dual-face measurements are present before processing set-of-angles reductions.

3.1.6.10. GSI Format Worked Example 

Below is a sample GSI16 file with three records: one station setup and two target observations.

*110001+0000000000STNA01 84..06+0000000004578321 85..06+0000000002345678 86..06+0000000000123456 88..06+0000000000015230
*110002+00000000000000P1 21.022+0000000012345600 22.022+0000000009523400 31..00+0000000000125340 87..06+0000000000016500
*110003+00000000000000P2 21.022+0000000045678900 22.022+0000000010034500 31..00+0000000000098760 87..06+0000000000016500

Line 1 (Station setup):

*110001+0000000000STNA01 – WI 11, point name = STNA01
84..06+0000000004578321 – WI 84, station easting = 457.8321 m (units code 6, 1/10 mm)
85..06+0000000002345678 – WI 85, station northing = 234.5678 m
86..06+0000000000123456 – WI 86, station elevation = 12.3456 m
88..06+0000000000015230 – WI 88, instrument height = 1.5230 m
No WI 21 or 22 present, so this is identified as a station setup record.

Line 2 (Observation to P1):

*110002+00000000000000P1 – WI 11, point name = P1
21.022+0000000012345600 – WI 21, Hz angle = 123.45600 gon (units code 2)
22.022+0000000009523400 – WI 22, Vz angle = 95.23400 gon (Face I, since < 200)
31..00+0000000000125340 – WI 31, slope distance = 125.340 m (units code 0)
87..06+0000000000016500 – WI 87, reflector height = 1.6500 m

Decoding the word 21.022+0000000012345600:

Position	Value	Meaning
1–2	`21`	Word Index: Horizontal angle
3	`.`	Auto-index: OFF
4	`0`	Input mode: measured
5	`2`	Additional info
6	`2`	Units: gradians (5 decimal places)
7	`+`	Sign: positive
8–23	`0000000012345600`	Raw value: 12345600, divided by 10^5 = 123.45600 gon

3.1.6.11. References 

Leica Geosystems – GSI Online for Leica TPS, instrument documentation
Total Open Station – GSI format description: https://totalopenstation.readthedocs.io/en/stable/input_formats/if_leica_gsi.html
Jaison’s Blog – Leica GeoSystem File Format (GSI File): https://jaisonjustus.wordpress.com/2011/02/13/leica-geosystem-file-format-gsi-file/