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CASE STUDY

Off-the-shelf Ground Control from CompassData for Precise Mapping in Correlator3D


CompassData has been surveying ground control points (GCPs) around the world since 1994, and in that time has amassed a catalogue of over 70,000 photo identifiable points. With varying degrees of accuracy these control points are available to users who need ground control but may not have the means to capture them. 

 

GCP Archive
INDUSTRY

Surveying


COUNTRY

Worldwide


USE CASE

GCPs are essential in producing and validating high quality map products. However, when GCPs were not collected during a project, existing ones may be an option. 


CHALLENGES
  • Surveying may not be a service performed in-house
  • Local survey may be more cost effective
  • Surveyors may be difficult to find in remote locations
  • Time constraints may not allow for new survey


BENEFITS
  • Mobilization without delay in survey
  • Deployment worldwide if GCPs are available at location
  • Processing without delay for ephemeris data
  • Rapid turnaround in accurate map products through Correlator3D
compassdata_inc_logo_round_corners
Philipp_CompassData_Headshot_Round

“When determining the number of GCPs needed, think of the person working downstream. Does adding 10% more GCPs make their life easier when generating maps products in a photogrammetry software such as Correlator3D? Then don’t hesitate to add more. Check to see if what we have in our CompassData catalogue is available to supplement what is needed on your projects.”

PHILIPP HUMMEL

VICE PRESIDENT AT COMPASS DATA

GCP Designation

WORKFLOW


Users of SimActive’s Correlator3D software can import GCPs in many common file formats at project setup or after the project has been initiated in the aerial triangulation (AT) module. In either case, measurement of the GCPs occurs in the AT module where the user can select a GCP to measure and designate it as a control point or a check point .  

If designated as a control point, Correlator3D will then use it in the bundle adjustment to constrain the project to the ground. If designated as a check point, the measurements will be withheld from the bundle adjustment process and measured against the resulting AT. All GCP residuals can be found in the AT report which appears upon completion of AT. 

Correlator3D’s AT report allows the user to review individual GCP residuals in a tabular format. A higher-than-average residual might mean a GCP is bad or was measured incorrectly. The user should disable it or remeasure it and rerun the bundle adjustment to see if the residual comes more in line with the overall average. If not it’s likely that it is a bad point and should be discarded . 

Once all GCP’s residuals fall within the desired range and the check points fall within the desired accuracy range, the user can exit the AT module and proceed with the other mapping modules to create the desired deliverables such as DSMs, DTMs, point clouds and orthomosaics.

Detailed Error

DELIVERABLES

Typical mapping deliverables include digital surface models, digital terrain models and orthomosaics. 

 

BENEFITS

The benefit of using CompassData’s GCP catalogue, or any GCPs for that matter, is to allow Correlator3D to tie mapping products to the real world with a level of accuracy needed to meet project requirements.

 

ABOUT COMPASSDATA

Formed in 1994 in Centennial Colorado, and Incorporated in 2003 as a Woman Owned Small Business CompassData is a family of companies led by Chief Executive Officer, Kate Schlatter and Executive Vice President, Hayden Howard. CompassData is proud to offer the industry’s largest commercially available archive of Ground Control Points around the world which can be used for orthorectification, airport mapping, data verification, and sensor calibration. For more information, visit www.compassdatainc.com.

Control Point

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