Survey tripods, tribrachs, prisms and poles: an accessories guide
Key takeaways
- Most survey tripods, tribrachs and poles use the 5/8" × 11 thread, so check compatibility before mixing accessories.
- Wooden tripods are steadier in heat and wind; aluminium tripods are lighter and cheaper.
- A tribrach's plummet and bubble drift out of adjustment and should be checked regularly.
- Every prism has a prism constant that must match the setting in the total station.
- A bent pole or misadjusted pole bubble causes errors that grow with pole height.
What does a survey tripod do and which type should you choose?
A survey tripod is the adjustable three-legged stand that supports a total station, GNSS receiver, level or prism over a ground point. Its job is to stay rigid and motionless for the whole observation, because any movement shifts the instrument and the measurement.
A surveyor's tripod has a flat head with a central fixing screw, usually 5/8" × 11 thread, telescopic legs with clamps, and pointed steel feet with foot pads for pushing into soil. Two materials dominate:
| Feature | Wooden surveyor's tripod | Aluminium survey tripod |
|---|---|---|
| Stability | Very good; dampens vibration | Good; can vibrate more in wind |
| Thermal behaviour | Little expansion in sun | Expands more with temperature change |
| Weight | Heavier | Lighter |
| Care | Needs protection from moisture | Low maintenance |
| Best for | Total stations, precise long observations | GNSS bases, levels, general work |
Our aluminium survey tripod has a 5/8" × 11 head, an adjustable height of about 90–158 cm and pointed steel feet.
How to set up a survey tripod over a point
A good tripod setup is level enough by eye, firm in the ground and close to centred before the instrument goes on. Time spent here saves time at the tribrach.
- Extend the legs to about chin height and tighten the clamps.
- Stand the tripod over the mark with the head roughly level and the legs evenly spread.
- Look down through the head hole and move the tripod until it is roughly over the point.
- Push each foot firmly into the ground, stepping on the foot pad.
- Attach the tribrach or instrument, centre with the plummet using the foot screws, then level by adjusting leg lengths.
- Finish levelling with the foot screws and re-check centring, repeating until both are correct.
On hard surfaces, use a tripod star or leg chain to stop the legs sliding. Never leave an instrument on a tripod unattended near traffic or in high wind.
What is a tribrach and how does it work?
A tribrach is the detachable base between the tripod and the instrument, used to level and centre it over a point. It has three foot screws, a circular bubble, an optical or laser plummet and a three-jaw locking mechanism.
Because the instrument locks into the tribrach and can be removed without disturbing it, surveyors use tribrachs for forced centring: swap a total station and a prism between tripods on a traverse, and each sits on exactly the same point. A tribrach adapter converts the tribrach to a 5/8" × 11 stub for GNSS antennas and some prisms, and can include a rotating carrier.
Our tribrach with adapter for GNSS and total station has three foot screws, a circular vial, an optical plummet and a 5/8" × 11 thread.
How to check a tribrach plummet
Centre and level the tribrach over a sharp mark, then rotate it 120° at a time on the tripod head, or rotate the plummet if it is in the instrument. If the crosshair leaves the mark in any position, the plummet needs adjustment.
What is the purpose of a surveying prism?
The purpose of a surveying prism is to return the total station's distance-measuring signal straight back to the instrument, so it can measure long distances accurately. A survey prism is a glass corner cube: light entering it is reflected back parallel to the incoming direction, even if the prism is not pointed exactly at the instrument.
Prisms extend range far beyond reflectorless mode. Our STSA9 total station, for example, measures up to 1500 m reflectorless but up to 5000 m to a single prism.
Prism types
- Standard circular prism – about 60 mm glass, used on poles and tribrachs for most work.
- Mini prism (miniature prism) – small prisms for stakeout, short ranges and tight spaces.
- 360° prism – used with robotic total stations so the prism need not face the instrument.
- Reflective targets – adhesive sheets for monitoring and close-range points.
Prism constant
Light travels more slowly in glass, so each prism has a prism constant (often 0 mm, −17.5 mm or −30 mm) that corrects the distance. If the constant set in the instrument does not match the prism, every distance is wrong by that amount.
Note: in road design, the "roadway prism" or "road prism" means the cross-section shape of a road between the cut and fill slopes, not a survey reflector.
Survey poles, prism poles and range poles
A survey pole is a telescopic rod that holds a prism or GNSS antenna vertically above a point at a known height. It is the most handled accessory on any crew, so build quality matters.
- Prism pole – carries a prism for total station work, with height graduations and a circular bubble.
- GNSS pole – a 5/8" × 11 top for a GNSS rover; common lengths are around 1.8 m to 2.6 m.
- Range pole – a painted ranging rod used for lining in and as a sighting target.
A bipod holds the pole steady for longer observations or precise stakeout. Our GNSS pole bipod uses quick-lock aluminium legs with rubber feet and steel points. A pole-mounted data collector bracket keeps the controller in view; ours adjusts through 360° and includes a compass.
Check the pole bubble often: hold the pole against a plumb reference or use a pole adjustment jig. A pole tilted by just 1° at 2 m height moves the top by about 3.5 cm. IMU tilt compensation in modern GNSS rovers reduces this problem, as explained in our guide to IMU tilt compensation.
Care and maintenance of survey accessories
Survey accessories are simple, but neglect turns them into hidden error sources. A short routine keeps them reliable.
- Clean mud from tripod and pole clamps and feet after use, and check that clamps lock firmly.
- Tighten tripod head hinges so the legs do not swing loosely.
- Check tribrach plummets and bubbles monthly or after any knock.
- Keep prism glass clean and dry; replace prisms with chipped faces.
- Store wooden tripods dry and away from long exposure to sun and rain.
- Label each prism with its constant.
Sourcing survey tripods and accessories
Accessories are inexpensive compared with instruments, but buying them alongside the instrument avoids thread and fit problems. Distributors often bundle them into kits.
Mars Geosystems supplies tripods, tribrachs, bipods, brackets and complete RTK accessory kits with an MOQ of one piece and OEM options. Ask for a quote for accessories on their own or with an instrument order.
Frequently asked questions
What is the difference between a tribrach and a tripod?
The tripod is the three-legged stand that supports the equipment above the ground. The tribrach is the levelling and centring base that screws onto the tripod head and holds the instrument. It has foot screws, a bubble and a plummet, so the instrument can be levelled and placed exactly over a ground mark, then swapped without disturbing the setup.
What thread does a survey tripod use?
Most survey tripods use a 5/8 inch × 11 threads per inch fixing screw, which is the common standard for total stations, levels, tribrachs and GNSS adapters. Some camera-style or light-duty tripods use different threads, so check before buying. Adapters exist, but a matched thread is more stable and less likely to come loose.
Why do surveyors use a prism?
Surveyors use a prism because it reflects the total station's distance signal straight back to the instrument, allowing accurate measurement over long distances and to precise points. Reflectorless measurement works on many surfaces but has shorter range and can be affected by angle, colour and texture. A prism on a pole also defines exactly where the point is.
What is a prism constant?
A prism constant is a distance correction that accounts for light travelling more slowly through the glass of the prism and for where the prism sits relative to its mounting point. Common values are 0 mm, −17.5 mm and −30 mm. It must be entered correctly in the total station, or every measured distance will carry that error.
Is a wooden or aluminium tripod better?
Wooden tripods are generally steadier and expand less in sun, so many surveyors prefer them for total stations and precise work. Aluminium tripods are lighter, cheaper and need less care, which suits GNSS bases, levels and general construction work. Both are fine when clamps are tight, feet are firmly set and the head is in good condition.
How do I check if my survey pole is straight and plumb?
Roll the closed pole on a flat surface to spot bends, then check the bubble by holding the pole against a plumb line or a pole adjustment jig. If the bubble is not centred when the pole is truly vertical, adjust or replace the vial. Repeat after any drop, because pole errors grow with pole height.
Need equipment for this work?
Tell us the job, the country and the quantity. An engineer replies with a configuration and price within one business day. MOQ is one unit; OEM is available.
