ISO 12858-3:2005

INTERNATIONAL ISO
STANDARD 12858-3
First edition
2005-02-01
Optics and optical instruments —
Ancillary devices for geodetic
instruments —
Part 3:
Tribrachs
Optique et instruments d'optique — Équipements annexes pour les
instruments géodésiques —
Partie 3: Embases
Reference number
©
ISO 2005
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ii © ISO 2005 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Type W tribrachs . 2
4.1 Nomenclature. 2
4.2 General features — Dimensions. 3
5 Type Z tribrachs . 6
5.1 Nomenclature. 6
5.2 General features — Dimensions. 7
6 Requirements. 9
6.1 General. 9
6.2 Connection between the tribrach and the tripod. 9
6.3 Torsional rigidity. 9
6.4 Foot screw. 10
6.5 Protection from corrosion. 10
6.6 Clamp knob or clamp screw . 10
6.6.1 Type W. 10
6.6.2 Type Z. 10
6.7 Circular level. 10
7 Designation and marking. 10
Annex A (informative) Recommendations for Type W tribrachs with improved stability. 11

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12858-3 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 6,
Geodetic and surveying instruments.
ISO 12858 consists of the following parts, under the general title Optics and optical instruments — Ancillary
devices for geodetic instruments:
 Part 1: Invar levelling staffs
 Part 2: Tripods
 Part 3: Tribrachs
iv © ISO 2005 – All rights reserved

Introduction
ISO 12858 consists of a series of parts which detail specifications for ancilliary devices to be used with
geodetic instruments in surveying. This third part specifies requirements for Tribrachs.
Additional parts, covering further ancillary devices, may be added to ISO 12858 as the need arises.
INTERNATIONAL STANDARD ISO 12858-3:2005(E)

Optics and optical instruments — Ancillary devices for geodetic
instruments —
Part 3:
Tribrachs
1 Scope
This part of ISO 12858 specifies the most important requirements of tribrachs used in geodesy for the
connection of the instrument's body with its base.
The requirements in this part of lSO 12858, however, do not guarantee the full interchangeability of the
instrument's body with tribrachs of different manufacturers, but give the detailed specifications of the clamp
system to ensure the reliable mounting and clamping without prejudicing their performance and their
usefulness. There are mainly two types of tribrach in use, categorized in this part of ISO 12858 as Types W
and Z.
This part of ISO 12858 is applicable to tribrachs which are used for levels, theodolites, tacheometers, GPS
equipment, EDM instruments and in combination with targets, reflectors, antennae etc.
2 Norma
...