ISO 9849:2026

International
Standard
ISO 9849
Fourth edition
Optics and optical instruments —
2026-05
Geodetic and surveying instruments
— Vocabulary
Optique et instruments d'optique — Instruments géodésiques et
d'observation — Vocabulaire
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Types of geodetic instruments and related terms .1
3.2 Parts of geodetic instruments .10
Bibliography .21
Index .22

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 6,
Geodetic and surveying instruments.
This fourth edition cancels and replaces the third edition (ISO 9849:2017), which has been technically
revised.
The main changes are as follows:
— definitions added for GPR, UAV, range camera, pole and marker;
— sub-categories added for GNSS, 3D laser scanner and graduated circle;
— editorial corrections.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document forms one of a series concerning geodetic and surveying instruments. It gives terms and
definitions which may be used in the drafting of other International Standards and national standards in
this field.
This document defines terms as they are used to describe geodetic and surveying instruments for geodetic
work and their essential parts. It is intended for both the surveyor and the non-surveyor. The use of these
definitions related to other fields may not be appropriate. Every reader is requested to use only these terms
in the future so that, with time, a standard and acceptable terminology will come into common usage.

v
International Standard ISO 9849:2026(en)
Optics and optical instruments — Geodetic and surveying
instruments — Vocabulary
1 Scope
This document defines terms relating to geodetic and surveying instruments, such as distance meters,
levels, theodolites, GNSS, total stations, laser scanners, airborne sensors and others, and their essential
components and accessories which are used in measuring operations, such as land surveying, topographic
surveying, construction surveying and engineering geodesy.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Types of geodetic instruments and related terms
3.1.1
alignment instrument
device used to aim at intermediate points and to a reference target at the end of an alignment
Note 1 to entry: The device is usually equipped with a powerful magnifying telescope (3.2.38).
3.1.1.1
alignment laser
alignment instrument (3.1.1) using a laser beam as reference line or reference plane instead of an optical line
of sight
3.1.1.1.1
point laser
plumb laser
pipe laser
alignment laser (3.1.1.1) which projects a single point on a surface using a reference line of a laser beam
3.1.1.1.2
line laser
laser marker
cone laser
cross-line laser
alignment laser (3.1.1.1) which projects one or more lines or planes on a surface using a reference plane of a
laser beam with a certain opening angle
Note 1 to entry: Instrument can be used for marking horizontal or vertical surfaces by a visible laser.
Note 2 to entry: A specific type of line laser for planar coverage is for example a rotating laser (3.1.16).

3.1.2
barometer
instrument for measuring atmospheric pressure
Note 1 to entry: Barometers can be used for the atmospheric reduction of electronically measured distances or as
barometric altimeters (3.1.2.2).
3.1.2.1
aneroid barometer
barometer (3.1.2) in which atmospheric pressure is balanced by some elastic elements as a method that does
not involve liquid
3.1.2.2
barometric altimeter
barometer (3.1.2) used for elevation measurement, in which case a read out is provided in metres
3.1.2.3
mercury barometer
barometer (3.1.2) in which atmospheric pressure is balanced by the mass of a column of mercury
3.1.2.4
electronic barometer
instrument for measuring atmospheric pressure by conversion of physical observation to electrical signals
3.1.3
electro-optical distance meter
electronic distance meter
EDM
instrument for measuring distances between the instrument and a reflective target, using various electro-
optical techniques, visible light or infrared radiation as carrier waves
Note 1 to entry: The target can be a reflector (3.1.15) or any other surface.
Note 2 to entry: See also total station (3.1.20), hand-held laser distance meter (3.1.7), terrestrial laser scanner (3.1.8.1)
and laser tracker (3.1.9).
3.1.3.1
phase shift distance meter
electro-optical distance meter (3.1.3) which is based on the phase comparison of two modulation signals, one
is the reference signal, the other the return signal from the reflective target
Note 1 to entry: The phase difference can be detected by various methods and is used to calculate the distance.
3.1.3.2
pulsed distance meter
time of flight distance meter
electro-optical distance meter (3.1.3) which is based on measuring the time of flight between transmission
and reception of the same pulse
3.1.4
field controller
tablet
data collector
device that controls a surveying instrument, such as total station (3.1.20), GNSS receiver (3.1.5.1), 3D laser
scanner (3.1.8) or digital level (3.1.10.2), by using on-board applications, recalls surveying data or other
information and records and analyses measurement data of the instruments

3.1.5
global navigation satellite system
GNSS
system consisting of several satellites in different orbital planes, which allow absolute navigation solutions
as well as high precise (e.g. differential) positioning and broadcasting of time due to the global coverage
Note 1 to entry: GNSS includes all operating global navigation systems by satellite.
EXAMPLE 1 Global positioning system (GPS) or navigational satellite timing and ranging – Global positioning
system (NAVSTAR-GPS) – US Department of Defence navigation system based on the constellation of usually more
than 24 satellites at an altitude of 20 200 km above earth’s surface.
EXAMPLE 2 GLObal’naya NAvigationnaya Sputnikovaya Sistema (GLONASS) – Russia's global navigation satellite
system based on the constellation of approximately 24 satellites at an altitude of 19 100 km above earth’s surface.
EXAMPLE 3 Galileo – Global navigation satellite system organized by EU and European Space Agency. The system is
planned to consist of 30 satellites at an altitude of 23 200 km above earth’s surface.
EXAMPLE 4 BeiDou – Navigation satellite system (BDS) organized by China. More than 54 satellites in medium
earth orbit (22 000 km above earth’s surface) as well as in geosynchronous orbit (35 790 km above earth’s surface) are
used, where the latter include satellites in both geostationary orbit and in inclined geosynchronous orbit.
EXAMPLE 5 Quasi-Zenith Satellite System (QZSS) – Satellite navigation system operated by Japan. The system
complements GPS, especially in the Asia-Pacific region, and consists of a constellation of typically 4 satellites in
geostationary orbit as well as highly elliptical, quasi-zenith orbit (32 600 km to 38 950 km above earth’s surface).
3.1.5.1
GNSS receiver
electronic device that receives and digitally processes the signals from GNSS satellites in order to provide
position, velocity and time (of the receiver)
3.1.5.2
differential GNSS
DGNSS
processing application within mobile GNSS receivers, using difference techniques of GNSS observations and
additional reference point or reference network GNSS observations
Note 1 to entry: In differential GNSS (DGNSS) applications, correction data and additional information from a known
reference station are used by mobile rovers, enabling them to improve position accuracy.
3.1.5.2.1
differential GPS
DGPS
DGNSS (3.1.5.2) application using only observations from the GPS (Navstar satellite system) and additional
reference point or reference network GPS observations
3.1.5.2.2
differential BDS
DBDS
DGNSS (3.1.5.2) application using only observations from the BDS (BeiDou navigation satellite system) and
additional reference point or reference network BDS observations
3.1.5.3
real-time kinematic
RTK
real-time processing algorithm technique of mobile GNSS receivers using the carrier phase of GNSS
observations for a positioning of the mobile GNSS receiver within a reference network in a low cm-level
Note 1 to entry: In real-time kinematic (RTK) application, measurements of the phase of the signal’s carrier wave are
used to provide real-time corrections. By a data link from the reference station to the rover station, the corrections
are transmitted to enhance the precision of the position up to cm-level.

3.1.5.4
GNSS measuring instrument
measuring equipment for the determination of coordinates on the basis of satellite-supported positioning
Note 1 to entry: A GNSS measuring instrument consists, e.g., of GNSS antenna, GNSS receiver (3.1.5.1), and field
controller (3.1.4).
3.1.5.5
choke ring antenna
type of omnidirectional antenna, consisting of a central antenna element surrounded by several concentric
conductive rings, which eliminate multipath signals
Note 1 to entry: Typically used for GNSS applications which require highest accuracy such as reference stations.
3.1.5.6
continuously operating reference station
CORS
GNSS reference station or its network system which continuously provides raw satellite observations and
positioning information in real-time
3.1.5.7
virtual reference station
VRS
method of using a network of physical reference stations to interpolate and transmit correction data of a
virtually established reference station in the vicinity of the mobile GNSS receiver (3.1.5.1)
Note 1 to entry: VRS can be used e.g. for both RTK (3.1.5.3) and post-processing applications.
3.1.6
gravimeter
gravity meter
gravity instrument
instrument for measuring the absolute gravity or the differences in the value of gravity
3.1.7
hand-held laser distance meter
electro-optical distance meter (3.1.3) which is used and held usually with the hands
Note 1 to entry: Usually, reflectorless EDM techniques are used.
3.1.8
3D laser scanner
measuring equipment using a scanning technology by a laser beam to produce detailed 3D point cloud data
including intensity of complex structures and objects and geometries
3.1.8.1
terrestrial laser scanner
TLS
3D laser scanner (3.1.8) which is set up as a ground-based instrument
3.1.8.2
airborne laser scanner
airborne topographic scanner
3D laser scanner (3.1.8) which is set up on an aircraft to scan the earth’s surface while flying
3.1.8.3
hand-held laser scanner
3D laser scanner (3.1.8) which is set up as mobile instrument to scan the surrounding while carried by
operator
3.1.9
laser tracker
coordinate measuring system in which a cooperative target is followed with a laser beam and its location
determined in terms of a distance (range) based on laser interferometry techniques and two angles
Note 1 to entry: Cooperative target can be a retroreflector (3.1.15.1).
3.1.10
level
instrument for measuring differences in height by establishing horizontal lines of sight, comprising as main
components a telescope (3.2.38) which can be rotated on a vertical axis (3.2.44) and a facility for levelling the
line of sight
Note 1 to entry: It can be additionally fitted with a horizontal circle (3.2.7) and/or a parallel plate micrometer (3.2.23).
The reticule has sometimes stadia hairs for optical distance measurement.
Note 2 to entry: See also spirit level (3.2.16) and tachymeter (3.1.17).
3.1.10.1
automatic level
compensator level
self-levelling level
pendulum level
level which makes use of a tilt compensator (3.2.39) that ensures that the line of sight is horizontal once the
operator has roughly levelled the instrument
3.1.10.2
digital level
level which electronically reads a sequence of code patterns on the levelling staff (3.1.11) by an image sensor
Note 1 to entry: These instruments usually include data recording capability. The automation removes the requirement
for the operator to read a scale.
Note 2 to entry: The processing and the display of the results are taken by an integrated computer.
3.1.10.3
electronic level
inclinometer
tiltmeter
instrument which detects inclination or changes of inclination under the influence of gravity by the use of
electronic sensors
Note 1 to entry: For the realization as sub-component of an instrument, see electronic level (3.2.16.3).
3.1.10.4
tilting level
manual level
level which provides a tilting screw to establish a levelled line of sight
3.1.11
levelling staff
levelling rod
level rod
straight bar with a scale on a flat face
Note 1 to entry: The levelling staff can be made of, for example, metal, glass fibre or wood.
Note 2 to entry: The levelling staff is used to measure the vertical distance between a base point and the horizontal
line of sight of a level (3.1.10).

3.1.11.1
digital levelling staff
bar code staff
levelling staff (3.1.11) for levelling with a digital level (3.1.10.2) having a specified code patterns on the flat
face
3.1.11.2
invar levelling staff
precise levelling rod
invar rod
levelling staff (3.1.11) for precise levelling, having an invar strip with graduation lines or code patterns (bar
code)
−6
Note 1 to entry: Invar is a Fe-Ni alloy to ensure a low coefficient thermal expansion (<10 /K).
3.1.12
optical plummet
instrument or device that realizes a visible line of sight in a vertical zenith or nadir direction
Note 1 to entry: The optical plummet can be levelled by liquid horizon, tubular levels or compensators.
Note 2 to entry: An optical plummet can also be a part of a geodetic instrument.
Note 3 to entry: It can be used for placing a marker (3.1.23) on the ground or centring an instrument over a marker
(3.1.23) on the ground (nadir plummet) as well as for centring an instrument under a point (zenith plummet).
3.1.12.1
laser plummet
optical plummet (3.1.12) which uses a laser beam as a visual plumb line
Note 1 to entry: A laser plummet can also be combined with an electro-optical distance meter (3.1.3) for measuring the
instrument height above ground.
3.1.12.2
optical precise plummet
optical plummet (3.1.12) comprising a telescope with high magnification and precise devices (e.g. bubbles,
compensator) to precisely realize the vertical line of sight
3.1.13
optical square
pentaprism
device equipped with pentagonal prism for determination of orthogonal lines of sight
3.1.14
plane table
device used in surveying and related disciplines to provide a solid and level surface on which to make field
drawings, charts and maps
Note 1 to entry: As a sighting instrument, usually, an alidade is used on the plane table.
Note 2 to entry: See also 3.2.27 for a description for a plane table as a part.
3.1.15
reflector
device at the target which reflects the light beam to an electro-optical distance meter (3.1.3) or to a tracker
system
Note 1 to entry: These devices are, for example glass prism reflectors, corner cube reflectors, acrylic reflectors,
reflecting sheets.
Note 2 to entry: Reflectors are usually provided on a pole (3.1.22) having a centring device. A 360° reflector device has
multiple glass prisms which are measurable from any horizontal direction.

3.1.15.1
retroreflector
passive device designed to reflect light back parallel to the incident direction over a range of incident angles
Note 1 to entry: These devices are, for example glass prism reflectors, corner cube reflectors.
3.1.15.2
reflective tape
reflecting tape
reflecting sheet
reflector (3.1.15) of plane sheet or tape comprised of tiny prisms made of a flexible material
3.1.16
rotating laser
laser level
rotary laser
instrument generating a plane by means of a rotating laser beam
3.1.17
tachymeter
tacheometer
instrument for measuring horizontal directions, vertical angles and distances
Note 1 to entry: A tachymeter is basically a theodolite (3.1.19) enhanced with the capability to measure distances.
3.1.18
target
target plate
symmetrical figure, structure or reflector defining a point on the target to which observations are taken
Note 1 to entry: It is usually provided with some form of a forced-centring device (3.2.13).
3.1.19
theodolite
transit
optical instrument for measuring horizontal directions and vertical angles, whose main components are
the horizontal circle and the vertical circle inclusive reading systems, the telescope (3.2.38) and the alidade
(3.2.1) inclusive the horizontal and vertical rotation axes
Note 1 to entry: The telescope can be rotated around the horizontal axis (3.2.15) and vertical axis (3.2.44).
Note 2 to entry: A theodolite can also be used for optical distance measurement.
Note 3 to entry: A theodolite used in astronomical work is usually termed an astronomical theodolite or a transit
instrument.
3.1.19.1
compass theodolite
compass transit
theodolite (3.1.19) attached with a centrally mounted compass (3.2.6) for determining the magnetic azimuth
3.1.19.2
electronic theodolite
theodolite (3.1.19) with microprocessor(s), display and memory for automatic reading, processing, displaying
and storing of measurement data

3.1.19.3
gyrotheodolite
gyro-azimuth theodolite
survey gyroscope
theodolite (3.1.19) with a north-seeking gyro attached for the determination of the geographic north
direction
Note 1 to entry: In general, both theodolite and gyro form one unit. Different observation methods allow to determine
the geodetic azimuth.
3.1.19.4
suspension theodolite
theodolite (3.1.19) in a hanging position to carry out measurements in the region of nadir, prior used for
mining surveys
3.1.20
total station
electronic tachymeter
electronic tacheometer
tachymeter (3.1.17) with microprocessor(s), display and memory for opto-electronic distance measurement,
angle reading, processing, displaying and storing of measurement data
3.1.20.1
multistation
combination of the functionality of a total station (3.1.20), terrestrial laser scanner (3.1.8.1) and of imaging in
one instrument
Note 1 to entry: A multistation (3.1.20.1) has often the possibility to attach or integrate a GNSS, wireless transmission
techniques and other devices used for surveying.
3.1.20.2
non-prism total station
reflectorless total station
total station with capability to measure the distance to almost any object without the need of a specific
reflector
3.1.20.3
gyro total station
total station with a north-seeking gyro attached for the determination of the geographic north direction
3.1.20.4
double-image tacheometer
tacheometer (3.1.17) with the optical wedge system included in the path of the rays in the telescope (3.2.38)
Note 1 to entry: It divides the image of a horizontal staff into two horizontally displaced images. The size of the
displacement is the index of the distance reduced for the difference in height.
3.1.21
tripod
three-legged stand to which instruments or accessories can be attached and set up in a stable manner on the
ground
Note 1 to entry: The tripod consists of a head and three legs made of wood or metal, with metal tips. The legs are either
rigid or telescopic and connected with the tripod head by joints. The tribrach (3.2.41) is fixed on the head of the tripod.

3.1.22
pole
range pole
reflector pole
GNSS pole
straight rod which is used to project points of interest to a different working height
Note 1 to entry: Can be used for example with reflectors (3.1.15) or GNSS receivers (3.1.5.1) which are attached to the
pole.
Note 2 to entry: Often a pole is extendable, includes a printed height scale and an analogue bubble for levelling.
Note 3 to entry: A pole can also include sensors to measure the height extend and/or the amount of tilt, for example.
3.1.23
marker
marking
indication of a measured or staked out point in the region of interest
Note 1 to entry: Short-term markers with a foreseeable limited usage period are used, for example, to lay out design
data in the process of building construction or to set temporary ground control points (GCPs) during photogrammetric
measurement sessions.
Note 2 to entry: Long-term markers with an indefinite usage period, such as a survey marker (3.1.23.1), are stably
anchored objects which mark key survey points of known position on the Earth's surface.
Note 3 to entry: Examples of markers can be printed or engraved indicators, physical objects or projected light.
3.1.23.1
survey marker
geodetic mark
permanent and solid object indication of a key survey point of known position on the Earth's surface
Note 1 to entry: Often represented by metal disks set in concrete or border stones used e.g. as triangulation point or
benchmark in geodesy and land surveying.
3.1.23.2
reference marker
reference mark
survey marker (3.1.23.1) of highest-grade, independently verified accuracy
3.1.24
hydrostatic level
level that consists of two or more glass tubes connected by flexible tubing filled with a fluid whose surfaces
in the glass tubes define a reference level
Note 1 to entry: Device typically consisting of two static heads of liquid, to measure changes in height by hydrostatic
pressure difference.
Note 2 to entry: This device can be used for deformation measurement of buildings and structures.
3.1.25
ground penetrating radar
GPR
device that transmits electromagnetic energy into the ground which is reflected, refracted, or scattered
back to the surface depending on the features it encounters
Note 1 to entry: can be used for measuring subsurface location and thickness of natural structures, such as rock, ice or
snow layers, or urban structures such as pipes, cables or masonry.

3.1.26
mobile mapping system
MMS
moveable measurement system generating geo-referenced observation data using multiple sensor systems
Note 1 to entry: MMS are frequently used to investigate and document the state of infrastructure.
Note 2 to entry: Unmanned aerial vehicles (3.1.27) are often typical MMS platforms.
3.1.27
unmanned aerial vehicle
UAV
unmanned aircraft system
UAS
remotely or autonomously controlled flight system
Note 1 to entry: UAVs can typically carry surveying instrumentation such as a digital aerial camera (3.2.48), 3D laser
scanner (3.1.8), GNSS receivers (3.1.5.1) and IMUs (3.2.49).
Note 2 to entry: UAVs typically can be classified into single-rotor, multi-rotor, fixed-wing and hybrid design.
3.2 Parts of geodetic instruments
3.2.1
alidade
turning board
DEPRECATED: alhidade, alhidad, alidad
device that allows one to sight a distant object and uses the line of sight to perform a task, consisting of
an upper part (3.2.42) or turning part of a theodolite or total station with telescope (3.2.38) which can be
rotated around the standing axes (3.2.44) with or without vertical circle and an opto-electronic distance-
measuring device
Note 1 to entry: This task can be, for example, to draw a line on a plane table (3.1.14) in the direction of the object or to
measure the angle to the object from some reference point.
3.2.2
base part
lower part
bottom part
centring flange
integrated group of parts of a theodolite (3.1.19) or the total station (3.1.20), supporting the limb (3.2.18) and
the upper part (3.2.42), and are firmly attached to the tribrach (3.2.41) during the measurement
Note 1 to entry: The base part consists essentially of the bearings for the vertical axis (3.2.44) and connecting devices
for the detachable tribrach.
3.2.3
base plate
lower part of the tribrach (3.2.41), connected by screws to the spring plate (3.2.36) and the foot screws
(3.2.12), which rest on this metal plate
3.2.4
circle drive
device for turning the horizontal and vertical circle of a theodolite (3.1.19) or total station (3.1.20) [usually
the telescope (3.2.38)] in relation of the fixed parts

3.2.5
clamp
device which enables rotating parts of the instrument to be clamped together when precisely sighting a
target, usually with clamps on the horizontal and vertical axis circles
Note 1 to entry: There are different types of clamps: central clamp, coa
...