Ushikata LS-25 O-BAC Zero-Setting System Explained Malaysia
Ushikata LS-25 O-BAC Zero-Setting System Explained Malaysia
When checking the specifications of the Ushikata LS-25 surveying compass, buyers may notice an unusual term:
“O-BAC Zero-Setting System.”
What does this mean, and why is zero setting useful when measuring horizontal angles?
The Ushikata LS-25 combines a magnetic compass, 12× telescope, horizontal and vertical angle measurement, levelling and stadia capabilities.
Its horizontal-angle system is specified with a 5′ graduation and O-BAC zero-setting system.
For surveyors, forestry teams and plantation users, understanding the purpose of zero setting makes it easier to understand how the LS-25 differs from a simple magnetic compass.
What Is Zero Setting in Angle Measurement?
Imagine that you want to measure the horizontal angle between two targets.
You have:
Point A — Instrument position
Point B — Reference target
Point C — Second target
Instead of being interested in the absolute circle reading at Point B, you may want to treat the direction toward B as your starting reference.
Conceptually:
Reference Target B = 0°
Then rotate toward:
Target C = Measured Horizontal Angle
This makes the resulting reading easier to interpret as the angle between two selected directions.
What Is the O-BAC System on the Ushikata LS-25?
Ushikata specifies the LS-25 horizontal graduation as:
5′ — O-BAC Zero-Setting System
The important practical point is that the system provides a method for establishing a zero reference for horizontal-angle observation.
This is different from simply reading magnetic direction from the compass circle.
For exact operating procedures and the internal mechanism of the O-BAC system, users should refer to the manufacturer's instructions rather than assuming that all zero-setting systems operate identically.
Why Is Zero Setting Useful?
Consider a simple field example.
You are standing at an observation point and want to determine the horizontal angle between:
Target 1 — Survey Marker
and
Target 2 — Ranging Pole
You first establish Target 1 as the reference direction.
Then you observe Target 2.
The horizontal-angle system allows the relationship between those two directions to be measured.
This is useful because surveyors frequently need relative angles between field points, not only compass bearings.
Bearing and Horizontal Angle Are Not the Same
This distinction is important when considering the LS-25.
Magnetic Bearing
Answers a question such as:
“In what magnetic direction is this target?”
Horizontal Angle
Answers:
“What is the angular difference between these two directions?”
The Ushikata LS-25 provides capabilities for both types of observation.
That is one reason it belongs in the category of professional surveying compass / Level Tracon, rather than being treated as an ordinary navigation compass.
What Does 5′ Graduation Mean?
The horizontal graduation of the LS-25 is specified as 5′.
The symbol ′ means an arc minute.
Angular measurement is divided as:
1° = 60′
Therefore:
5′ = 5 arc minutes
This is an angular unit.
It does not mean five minutes of time.
5′ vs 1° — Why Are Both Listed for the LS-25?
Buyers sometimes see both specifications and assume they refer to the same scale.
They do not.
The LS-25 specifications include:
Horizontal Graduation — 5′
and
Compass Circle — 70 mm / 1° graduation
These relate to different observation functions.
This is another reason buyers should avoid judging a surveying compass from a single specification.
LS-25 Horizontal Angle vs Compass Bearing
FunctionPurposeMagnetic CompassEstablish magnetic direction / bearingCompass CircleDirectional observationHorizontal Angle SystemMeasure angular relationship between directionsO-BAC Zero SettingEstablish a reference for horizontal-angle observation12× TelescopeSight the selected target
Together, these functions provide more flexibility than a conventional compass.
Why Does Telescope Sighting Matter?
An angle measurement is only meaningful when the operator is observing the correct target.
The Ushikata LS-25 incorporates a 12× erect-image telescope.
This allows the operator to identify and sight field targets such as:
Survey markers
Ranging poles
Reference points
Selected trees
Terrain features
Temporary targets
This can be especially useful in forestry or plantation environments where field features may be difficult to distinguish.
Example: Forestry Survey
Imagine a forestry team needs to observe the angle between two field directions.
From the observation point:
Direction A → Existing survey marker
Direction B → Proposed route
The operator can establish the required reference toward the first direction and then observe the second direction.
The horizontal-angle measurement provides information about the relationship between those directions.
At the same time, the compass can provide directional information where required.
Example: Plantation Reconnaissance
A plantation team may be investigating:
Existing access road
versus
Proposed new route
A preliminary field observation may require the team to understand how much the proposed route changes direction relative to the existing alignment.
A horizontal-angle capability can assist with this type of reconnaissance.
If the project later requires precise engineering coordinates, road setting-out or detailed construction data, a Total Station or other appropriate surveying system should be used.
Does O-BAC Make the LS-25 a Total Station?
No.
Zero setting and horizontal-angle measurement do not make the LS-25 equivalent to a modern Total Station.
A Total Station provides functions such as:
Electronic Distance Measurement
Precise electronic angle measurement
Coordinate calculation
Construction setting-out
Digital data storage
Topographic surveying
The LS-25 remains a compact optical-mechanical surveying compass designed for a different type of fieldwork.
Does the LS-25 Still Have a Magnetic Compass?
Yes.
The LS-25 incorporates a 70 mm compass circle with 1° graduation.
This provides magnetic directional capability in addition to its horizontal-angle functions.
Users should therefore remember that magnetic observations can be influenced by nearby magnetic or ferrous objects.
Avoid taking critical compass observations immediately beside:
Vehicles
Steel structures
Heavy machinery
Metal fencing
Strong magnets
Other significant sources of magnetic interference
Ushikata LS-25 Main Specifications
SpecificationUshikata LS-25Telescope12× erect imageHorizontal Graduation5′Horizontal SystemO-BAC Zero SettingCompass Circle70 mmCompass Graduation1°Vertical CircleFull circle / 1° graduationBubble Sensitivity5′ / 2 mmApprox. Weight with Case1.3 kgOriginJapan
Who Needs Horizontal Zero Setting?
This type of functionality can be relevant to users involved in:
Forestry Survey
Plantation Survey
Land Reconnaissance
Terrain Observation
Environmental Fieldwork
Agricultural Survey
Geological Survey
Research & Education
Preliminary Route Survey
The important question is whether the user needs relative horizontal-angle measurement in addition to magnetic bearing.
Frequently Asked Questions
What is O-BAC on the Ushikata LS-25?
It is the zero-setting system associated with the LS-25 horizontal-angle measurement system.
What is the horizontal graduation of the LS-25?
The specified horizontal graduation is 5′.
Is 5′ the same as 5°?
No.
1° = 60′, so 5′ represents five arc minutes.
Is the compass also graduated at 5′?
No. The LS-25 compass circle is separately specified as 70 mm with 1° graduation.
Can the LS-25 measure vertical angles?
Yes. It incorporates a full-circle vertical scale with 1° graduation.
Can it measure electronic distance?
No. The LS-25 has stadia capability but is not an EDM Total Station.
Can it provide coordinates?
Not by itself. For coordinate surveying, consider suitable Total Station or GNSS/RTK equipment.
Ushikata LS-25 Supplier Malaysia
MTM Precision supplies professional surveying instruments and accessories for customers in Malaysia.
Our surveying range includes solutions for:
Direction & Bearing
Horizontal / Vertical Angles
Levelling
Electronic Distance Measurement
Construction Setting-Out
Monitoring
Forestry & Plantation Surveying
Products include Ushikata, Myzox and Topcon surveying equipment, together with levelling staffs, prisms, tripods and surveying accessories.
If you are unsure whether the Ushikata LS-25 provides the measurement functions your project requires, send us the application before ordering.
Contact MTM Precision
MTM Precision Sdn. Bhd. (744811-A)
Telephone: +603-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com / enquiry@mtmpre.com.my
Website: www.mtmpre.com.my
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Contact MTM Precision for Ushikata LS-25 price, quotation, availability and technical enquiries in Malaysia.
16 Sep 2026
