How Many Ground Control Points (GCPs) Do You Need for Drone Mapping Malaysia?
How Many Ground Control Points (GCPs) Do You Need for Drone Mapping Malaysia?
Content
How Many Ground Control Points Do You Need for Drone Mapping Malaysia?
GCP Quantity, Placement & Check Points for UAV Survey and Photogrammetry
One of the most common questions when starting a drone survey is:
“How many Ground Control Points should I use?”
There is no single fixed number of GCPs that is correct for every drone mapping project.
The appropriate number depends on the site size, site shape, terrain, required accuracy, flight configuration, positioning system and survey methodology.
MTM Precision supplies reusable 50×50cm, 100×100cm and 150×150cm GCP targets in Malaysia for drone survey, UAV mapping and photogrammetry applications.
QUICK ANSWER: Do not decide GCP quantity based only on acreage or hectares. Good GCP distribution, accurate coordinate measurement and independent Check Points can be more important than simply adding more targets.
Is 5 GCPs Enough for Drone Mapping?
You will often hear recommendations such as:
“Just use 5 GCPs.”
That may work for some projects, but it should not be treated as a universal rule.
A simple, relatively flat and compact project area is very different from:
• A long highway corridor
• A large quarry
• A hilly construction site
• A plantation
• An irregular land parcel
• A site with major elevation differences
The same number of GCPs can produce very different control geometry on different sites.
More GCPs Do Not Automatically Mean Better Accuracy
This is important.
20 poorly measured or poorly positioned GCPs are not automatically better than a smaller number of accurately surveyed, well-distributed control points.
Drone mapping quality can be influenced by:
✓ Coordinate accuracy
✓ GCP distribution
✓ Image geometry
✓ Image overlap
✓ Camera quality
✓ GNSS/RTK solution quality
✓ Terrain
✓ Processing methodology
✓ Independent accuracy verification
Therefore:
GCP quantity should be designed as part of the survey methodology—not treated as a simple “more is better” decision.
GCP Distribution Matters
Imagine a large site where every GCP is placed close to the take-off point.
You may have many accurately surveyed targets, but the control is poorly distributed across the mapping area.
A better control layout generally considers:
• Project perimeter
• Interior of the project area
• Site corners
• Changes in elevation
• Irregular geometry
• Areas where stronger control may be required
The objective is not to create the highest number of GCPs. The objective is to create appropriate spatial control for the project.
GCP Placement for a Simple Rectangular Site
For a simple compact mapping area, surveyors may consider distributing control around the project rather than concentrating it in one location.
Conceptually:
GCP ————— GCP
** GCP**
GCP ————— GCP
This illustrates a common idea:
Control around the perimeter plus suitable internal control can provide better spatial distribution than clustering all targets together.
However, the actual design must follow the project's survey requirements.
What About Large Sites?
As the mapping area increases, the control strategy may need to change.
Larger sites can introduce:
• Longer distances between control points
• Greater terrain variation
• More complex flight blocks
• Different ground conditions
• Greater image-network complexity
Do not simply scale a small-site GCP layout to a large project without considering the survey geometry.
Long Road & Infrastructure Projects Need Different Thinking
A road, railway, pipeline or utility corridor has very different geometry from a square construction site.
For corridor mapping, control may need to be distributed along the length of the project, rather than only near the beginning and end.
Applications include:
ROAD CONSTRUCTION
HIGHWAY PROJECTS
PIPELINE CORRIDORS
UTILITY PROJECTS
RAILWAY MAPPING
DRAINAGE & INFRASTRUCTURE
Project shape matters when determining GCP quantity and placement.
Terrain & Elevation Matter Too
A flat site and a hilly site should not automatically use the same control strategy.
Sites with significant elevation variation may require additional consideration of the vertical distribution and overall geometry of control.
Examples include:
• Quarry faces
• Cut-and-fill areas
• Hilly developments
• Embankments
• Large stockpile zones
Drone mapping is three-dimensional. GCP planning should not consider horizontal position alone.
GCP vs Check Point
Another reason not to use every available target as a GCP is that some surveyed points can be reserved as Check Points.
Ground Control Point
A GCP is normally used as known control within the photogrammetric adjustment.
Check Point
A Check Point is normally excluded from the adjustment and used afterwards to assess the mapping result independently.
If every surveyed target is used as control, you may lose an important opportunity to independently evaluate the result.
Why Check Points Matter
Suppose your photogrammetry software reports a good fit to the GCPs.
That tells you something about how the model fits the control used in processing.
But professional users may also want to know:
“How accurately does the processed model reproduce surveyed points that were NOT used to control it?”
That is where independent Check Points become valuable.
GCPs help control the model. Check Points help evaluate it.
Do RTK Drones Need GCPs?
Modern RTK/PPK drones can significantly improve image geolocation.
But the answer is not simply:
RTK = No GCP Needed
The appropriate approach depends on:
• Required deliverable
• Accuracy specification
• RTK/PPK workflow
• Base/network conditions
• Project risk
• Client requirements
• Need for independent verification
Even when fewer or no GCPs are used as control, independently surveyed Check Points can still be valuable for verifying the result.
How Many GCP Targets Should You Physically Own?
This is slightly different from asking how many GCPs should be used on one project.
A drone survey company may benefit from owning more physical targets than the typical number used as control.
Why?
Because targets may be used as:
• GCPs
• Check Points
• Replacement targets
• Additional control for unusual site geometry
• Additional targets for larger projects
Reusable GCP targets allow the same set to be deployed repeatedly across different projects.
Which GCP Size Should You Use?
MTM Precision offers:
50 × 50cm
Best advantage: PORTABILITY
Useful when compact targets remain clearly visible under the planned imaging conditions.
100 × 100cm
Best advantage: BALANCE
Our practical general-purpose starting option for many drone survey applications.
Suitable for construction, land development, earthwork and general UAV mapping.
150 × 150cm
Best advantage: LARGER VISUAL TARGET
Useful where project conditions benefit from a larger ground target.
Can You Mix GCP Sizes?
Potentially, yes.
A survey team may own different target sizes for different types of projects.
For example:
50×50cm — compact projects
100×100cm — general projects
150×150cm — applications requiring a larger target
However:
Consistency of the defined reference point is more important than simply having different target sizes.
The exact point surveyed on the ground should correspond consistently with the point identified in the imagery.
GCP Target Size Does Not Determine GCP Quantity
This distinction is important:
SIZE = VISIBILITY
QUANTITY + DISTRIBUTION = CONTROL GEOMETRY
A 150×150cm target does not automatically mean you can use fewer control points.
Likewise, using many 50×50cm targets does not solve a visibility problem if they cannot be identified reliably in the images.
Before Planning Your GCP Layout, Ask These Questions
1. What is the shape of the site?
Compact, long corridor, irregular or fragmented?
2. How large is the project?
A small construction site and a large plantation require different planning.
3. Is the terrain flat?
Elevation variation can affect control strategy.
4. What accuracy is required?
Different deliverables can have different requirements.
5. Is the drone RTK/PPK equipped?
The positioning workflow affects how ground control may be used.
6. How will accuracy be checked?
Consider reserving independently surveyed Check Points.
7. Will every target be visible?
Target size, GSD, surface contrast and obstruction must be considered.
Common GCP Planning Mistakes
MISTAKE 1 — Using a Fixed Number for Every Job
“We always use five.”
The project geometry may not support that assumption.
MISTAKE 2 — Putting All GCPs Around the Edge
Depending on the site, interior control may also be important.
MISTAKE 3 — Clustering GCPs Together
More targets in one small area do not necessarily create stronger control across the whole site.
MISTAKE 4 — Using Every Target as Control
This may leave no independent Check Points for accuracy evaluation.
MISTAKE 5 — Poor Coordinate Measurement
A clearly visible GCP with an inaccurate coordinate is still an inaccurate control point.
MISTAKE 6 — Choosing Targets Too Small to Identify
A physical target must remain identifiable in the actual aerial imagery.
Ground Control Point Applications in Malaysia
Reusable GCP targets can support drone mapping for:
CONSTRUCTION PROJECTS
EARTHWORK & CUT/FILL
TOPOGRAPHIC SURVEY
ROAD & HIGHWAY PROJECTS
LAND DEVELOPMENT
QUARRY & STOCKPILE MAPPING
PLANTATION MAPPING
INFRASTRUCTURE PROJECTS
GIS & AERIAL MAPPING
Frequently Asked Questions
How many GCPs do I need per hectare?
There is no universal GCP-per-hectare number suitable for every project.
Site geometry, terrain, flight configuration, positioning technology and accuracy requirements all matter.
Are 5 GCPs enough?
They may be sufficient for some workflows and insufficient for others.
Do not treat five as a universal specification.
Should I use all my targets as GCPs?
Not necessarily.
Some surveyed targets may be better reserved as independent Check Points, depending on the project methodology.
Does RTK eliminate GCPs?
Not universally.
The required ground-control and verification strategy depends on the project specification and workflow.
Does using more GCPs improve accuracy?
Not automatically.
Coordinate quality + appropriate distribution + good image geometry are more important than simply maximising target count.
Buy Ground Control Point Targets in Malaysia
MTM Precision supplies reusable GCP Targets for Drone Survey and UAV Mapping in Malaysia.
Available Sizes
50 × 50 cm — Compact
100 × 100 cm — General Purpose
150 × 150 cm — Large Target
For customers planning a set, tell us your:
Drone model
Application
Approximate flight parameters
Project type
and we can help you compare the available target sizes.
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 Ground Control Points and 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
