The difference between a map that is internally consistent and one that is tied to absolute real-world position — and how to tell which one your project needs. Applied across Fort Lauderdale, Miami, and West Palm Beach and throughout South Florida.
These get used interchangeably and they are not the same thing. Relative accuracy describes internal consistency: if you measure a 40-foot distance in one corner of the dataset and a 40-foot distance in the opposite corner, both are correct relative to each other. The whole model could be shifted several feet from true position and relative accuracy would be unaffected.
Absolute accuracy describes how closely the dataset matches actual real-world coordinates. A model with excellent relative accuracy and poor absolute accuracy is perfectly usable for measuring changes, comparing volumes, and tracking progress — and completely unusable for anything that must tie to a legal boundary, a control network, or a design datum.
Most construction documentation, progress tracking, and volumetric work needs relative accuracy and nothing more. Work that has to integrate with survey control or design coordinates needs absolute accuracy. Paying for the second when you need the first is waste. Accepting the first when you need the second produces a dataset your engineer cannot use.
A standard GNSS receiver on an aircraft is accurate to within a few meters. That is not close enough for mapping. RTK positioning corrects for that by comparing the aircraft's satellite readings against a fixed reference station at a precisely known location, calculating the error in real time, and applying the correction to each image's recorded position.
Sellers LP flies RTK-enabled using Florida's free open NTRIP correction network, which provides that reference infrastructure across the state without a dedicated base station on site. That coverage is one of the practical advantages of operating in Florida.
RTK substantially improves the positional quality of the captured imagery, and for many projects it is sufficient on its own. What it does not do is independently verify the result — it improves the input without providing a check on the output.
Ground control points are physical, high-contrast targets placed on the site at known surveyed coordinates. Because they appear in the captured imagery and their true position is independently established, processing can tie the entire dataset to real-world coordinates and, just as importantly, checkpoints can verify how well it did.
That verification is the part RTK alone cannot provide. GCPs give the licensed professional on your team something to validate against rather than a number they have to take on faith.
Placement takes time on site and adds to the field day, which is why it is specified per project rather than applied by default. The right approach is to let the surveyor or engineer who will use the data specify the accuracy requirement, then build the flight around that requirement rather than the other way around.
Ideal for: Licensed surveyors, professional engineers, civil firms, earthwork contractors, and project teams with defined accuracy specifications.
Any deliverable that has to tie to a control network, a design datum, or a legal boundary depends on how positioning was handled during capture.
Relative accuracy means measurements are internally consistent with each other across the dataset. Absolute accuracy means the dataset matches true real-world coordinates.
A model can have excellent relative accuracy while sitting several feet off true position. That is fine for measuring change and computing volumes, and unusable for anything tying to survey control.
RTK alone is sufficient for a great deal of construction documentation, progress tracking, and volumetric work. Ground control points are required when a project needs verified absolute accuracy tied to real-world coordinates.
The licensed surveyor or engineer who will use the data should specify which. That is an engineering decision, not a budget decision.
Florida's free open NTRIP network, which provides reference station coverage across the state without needing a dedicated base station set up on site. It is one of the genuine operational advantages of working in Florida.
No. RTK substantially improves the positional quality of the captured imagery, but it does not independently verify the finished dataset. Ground control points with checkpoints provide that verification, which is what lets your licensed professional validate the result rather than accept it on faith.
No. Accuracy is documented and the dataset is handed off with the information needed to evaluate it. Validation and certification are the responsibility of the licensed surveyor or professional engineer on your team.