How to Place Ground Control Points (GCPs) for Drone Survey Malaysia – GCP Placement Guide
How to Place Ground Control Points (GCPs) for Drone Survey Malaysia – GCP Placement Guide
Content
How to Place Ground Control Points (GCPs) for Drone Survey Malaysia
Practical GCP Placement Guide for UAV Mapping, Photogrammetry & Construction Survey
Where should you place Ground Control Points (GCPs) when carrying out a drone survey?
Correct GCP placement is important because having many targets does not automatically create good survey control.
A project with fewer, accurately surveyed and appropriately distributed GCPs can be more meaningful than simply placing many targets wherever they are convenient.
QUICK ANSWER: GCPs should generally be distributed across the mapping area according to the site geometry, terrain, elevation changes, flight plan and accuracy requirements. Avoid clustering all GCPs in one small part of the project.
GOOD GCP PLACEMENT = VISIBILITY + ACCURATE COORDINATES + APPROPRIATE DISTRIBUTION
Why Does GCP Placement Matter?
A GCP provides a known ground reference for the photogrammetric workflow.
But that control needs to represent the project area appropriately.
Imagine a large construction site with ten GCPs.
If all ten are positioned beside the site office because that location is easy to access:
You have many GCPs—but poor spatial distribution.
The number of targets alone does not solve this problem.
The Basic Principle of GCP Placement
For a simple project, think about distributing control across the area rather than concentrating it at one point.
A conceptual layout might look like:
GCP ───────────── GCP
** GCP**
GCP ───────────── GCP
This is only a simplified illustration.
The actual layout depends on:
• Project dimensions
• Project shape
• Terrain
• Elevation variation
• Flight configuration
• Required accuracy
• Applicable survey specifications
There is no universal GCP pattern suitable for every drone survey.
1. Place GCPs Around the Project Area
For suitable compact sites, control around different parts of the project perimeter can help provide spatial coverage.
Instead of:
GCP GCP GCP GCP GCP → all in one corner
consider distributing control around the area according to the project's survey design.
GCPs should represent the mapping area—not just the easiest places for the surveyor to reach.
2. Consider Interior GCPs
Perimeter control alone may not always be sufficient for every project.
Depending on the size and geometry of the mapping area, interior control may also be appropriate.
This is particularly relevant for:
• Large construction sites
• Wide land developments
• Quarry projects
• Large earthwork areas
• Irregular sites
Do not automatically assume that putting targets only at the four corners is the optimum layout.
3. Consider Elevation Changes
Drone mapping is not only about X and Y position.
Z — elevation — also matters.
Projects with substantial height variation require particular attention.
Examples include:
QUARRIES
HILLY DEVELOPMENT SITES
CUT & FILL PROJECTS
EMBANKMENTS
SLOPES
STOCKPILE AREAS
If every GCP is positioned on similar low, flat ground while the site contains large elevation changes, the control geometry may not adequately represent the complete project.
GCP planning should consider the three-dimensional nature of the terrain.
4. Avoid Clustering GCPs Together
This is one of the easiest mistakes to make.
Survey teams naturally prefer locations that are:
Easy to walk to
Close to the vehicle
Close to the take-off point
Easy for GNSS measurement
But convenience should not be the only consideration.
Five GCPs within a small area do not provide the same spatial control as appropriately distributed points across the project.
5. Make Sure Every GCP Is Visible From Above
A perfectly surveyed GCP is not useful for photogrammetry if you cannot identify it reliably in the drone imagery.
Avoid placing targets:
✗ Under trees
✗ Under machinery
✗ Beside objects that may cover the target
✗ In deep shadow where visibility becomes poor
✗ Where vehicles may park over them
✗ Where workers may move them
✗ In vegetation that hides the target
A GCP needs two things: a reliable surveyed coordinate AND reliable visibility in the imagery.
6. Choose a Surface With Good Contrast
Ground surface matters.
Common Malaysian project environments include:
Dark asphalt
Light concrete
Red soil
Grass
Sand
Crusher run
Quarry surfaces
The target pattern should remain clearly distinguishable from its surroundings.
High target-to-ground contrast can make GCP identification easier during image processing.
7. Secure the Target Properly
Outdoor drone mapping means dealing with:
Wind
Passing vehicles
Construction activity
Uneven surfaces
Workers and machinery
A target that moves after its coordinate has been surveyed can create a serious problem.
Once the GCP coordinate has been measured, the target reference point must remain in the same position for the relevant flight.
Where appropriate, secure the target according to its design and site conditions.
8. Survey the Correct Reference Point
This is critical.
Do not simply place the GNSS pole somewhere on the target.
The exact physical point measured in the field must correspond to the exact point identified later in the aerial images.
For a target with a defined centre:
Survey the defined reference centre consistently.
During processing:
Mark that same reference point consistently.
Consistency between field measurement and image marking is fundamental.
9. Do Not Put GCPs Too Close to Obstructions
Tall structures can create:
• Shadows
• Image occlusion
• GNSS limitations
• Multipath issues
• Difficult aerial visibility
Examples include:
Buildings
Trees
Cranes
Steel structures
Large machinery
When using GNSS/RTK to establish coordinates, also consider whether the location provides suitable satellite visibility and measurement conditions.
10. Keep Some Targets as Check Points
Not every surveyed target needs to become a GCP.
Depending on the project methodology, some can be reserved as independent Check Points.
GCP = CONTROL
CHECK POINT = VERIFY
A Check Point can help assess how the completed photogrammetric output compares with an independently surveyed ground coordinate.
Example: Construction Site GCP Placement
For a compact construction project, a conceptual strategy may include:
• Control around suitable parts of the perimeter
• Appropriate interior control
• Independent Check Points
• Consideration of elevation variation
Do not copy a fixed pattern blindly.
Adapt the control layout to the actual site.
Construction sites change continuously, so also consider:
Machinery movement
Temporary structures
Material stockpiles
Excavations
Access restrictions
Example: Road & Highway Drone Survey
Road projects are usually long and narrow.
This creates a different control problem.
Do not treat a 5 km road corridor like a square construction site.
Control may need to be distributed along the project corridor according to the survey methodology.
Applications include:
• Highway construction
• Road upgrading
• Drainage projects
• Pipeline corridors
• Utility corridors
• Railway projects
GCP placement should follow the geometry of the project.
Example: Quarry GCP Placement
Quarries can be particularly challenging because of:
Large elevation changes
Excavated faces
Stockpiles
Changing terrain
Dust
Heavy machinery
GCPs should be positioned where they are:
Clearly visible
Safe to access
Stable
Appropriately distributed
Never compromise site safety simply to achieve a theoretically ideal GCP position.
Example: Plantation Drone Mapping
Plantation environments introduce another challenge:
Finding clear ground that is visible from the air.
Vegetation can hide smaller targets.
Suitable placement may require open areas such as:
Roads
Clearings
Accessible open ground
depending on project conditions.
A larger GCP target may be worth considering where additional visual presence is beneficial.
Which GCP Size Is Best for Placement?
MTM Precision supplies three sizes.
50 × 50cm
BEST FOR PORTABILITY
Advantages:
✓ Easy to carry
✓ Compact storage
✓ Fast deployment
Use where it remains sufficiently visible under the project's imaging conditions.
100 × 100cm
BEST GENERAL-PURPOSE OPTION
Advantages:
✓ Good visual footprint
✓ Still practical to transport
✓ Suitable for many construction and land projects
For general drone survey applications, 100×100cm is our practical starting size.
150 × 150cm
BEST WHEN A LARGER VISUAL TARGET IS REQUIRED
Advantages:
✓ Larger ground footprint
✓ Greater visual presence
Useful when project conditions justify a larger target.
Important: GCP Size ≠ GCP Accuracy
This deserves repeating.
A larger target does NOT automatically produce a more accurate survey.
Target size primarily affects visibility and field handling.
Accuracy depends on the complete workflow, including:
Coordinate measurement
Control distribution
Image quality
Flight geometry
GNSS/RTK performance
Photogrammetry processing
Accuracy verification
Common GCP Placement Mistakes
MISTAKE 1 — All Targets Near the Take-Off Point
Easy for the pilot, poor representation of the project.
MISTAKE 2 — Targets Under Trees
The drone cannot reliably see them.
MISTAKE 3 — Target Moves After Surveying
The surveyed coordinate no longer corresponds to the target position.
MISTAKE 4 — Wrong Point Surveyed
The field coordinate and image-marked reference point do not match.
MISTAKE 5 — Ignoring Elevation
Drone mapping is 3D.
MISTAKE 6 — Using Every Point as a GCP
You may have no independent Check Points left for verification.
MISTAKE 7 — Choosing Targets Too Small for the Imagery
If you cannot reliably identify the reference point in the photographs, the target is not doing its job.
GCP Field Checklist
Before flying, check:
✓ Targets are correctly positioned
✓ Targets are securely fixed
✓ Reference centres have been surveyed
✓ Coordinates are correctly recorded
✓ Target IDs are clear
✓ Targets are visible from above
✓ GCPs are appropriately distributed
✓ Check Points are identified separately
✓ No machinery or vehicles are covering targets
✓ Flight plan covers the required targets
A five-minute field check can prevent an expensive re-flight.
Frequently Asked Questions
Should GCPs be placed at the corners?
Corners can form part of a control strategy for suitable project geometry, but four-corner placement should not be treated as a universal rule.
Should I put a GCP in the centre?
Interior control may be appropriate depending on the size, geometry and survey methodology of the project.
Can GCPs be placed on roads?
Potentially, if the location is safe, stable, visible and appropriate for the survey method.
Never place targets where they create a traffic or site-safety hazard.
Can I put GCPs on grass?
Potentially, but ensure the target remains flat, stable, clearly visible and unobstructed by vegetation.
What happens if a GCP moves?
If it moves after its coordinate was measured, the surveyed coordinate may no longer represent the target's actual position.
It should be checked and, where necessary, re-established and re-surveyed.
Buy Ground Control Point Targets in Malaysia
MTM Precision supplies reusable GCP Targets for Drone Survey, UAV Mapping and Photogrammetry in Malaysia.
Available Sizes
50 × 50cm — Compact
100 × 100cm — General Purpose
150 × 150cm — Large Visual Target
Suitable for:
Drone Survey | Construction | Earthwork | Topographic Mapping | Road Projects | Quarry | Plantation | Land Development | Infrastructure
Contact MTM Precision
MTM Precision Sdn Bhd
Website: www.mtmpre.com.my
Email: mtmpre@yahoo.com
WhatsApp: 016-660 7346
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Supplying GCP targets and professional surveying accessories throughout Malaysia, including Selangor, Kuala Lumpur, Johor, Penang, Perak, Negeri Sembilan, Melaka, Pahang, Kedah, Perlis, Terengganu, Kelantan, Sarawak and Sabah.
08 Sep 2026
