Make Geospatial Data More Accurate
When is Submeter Accuracy Required?
With the growing constellation of commercial earth-observation satellites, there has been an explosion of spatial data in our everyday lives. Once the realm of surveyors and rocket scientists, Global Positioning Satellite (GPS) technology is now in our automobiles, wristwatches, and cell phones, and is becoming increasingly tied to data, be it a satellite image of the Earth or the map location of the restaurant we just made reservations with while stuck in traffic. How does the satellite image and internet map display the restaurant within meters of its real location? GCPs. GCPs were used to geolocate the satellite image and the map that was digitized from the image and displayed in the application. This positional accuracy will become even more critical as we enter the age of driverless vehicles.
GCPs: Essential Foundation for Geospatial Accuracy
- Planimetric (GIS) Mapping
- Urban Planning / Engineering
- Natural Resource Management
- Utility Mapping
- UAV Navigation
- LiDAR and IFSAR Surface Models
- Image Orthorectification
- Airport Mapping Databases
- Sensor Calibration
- Surface Elevation Mapping
- Driverless Vehicle Navigation
Certified Quality Processes and Standardized GCP Deliverables
Per ISO and FAA certified quality processes, CompassData strives to meet and exceed the customer’s end project requirements:
- GCP survey planned to capture best suited feature types (photo-identifiable, LiDAR specific, permanent or temporary features)
- Accuracy tailored to end product accuracy requirements, see GCP Specifications
- Optimized density and distribution of GCPs
- Coordinate file containing Lat/Long and Elevation with data translated to the desired spatial reference and coordinate system
- Project Report (optional) containing information on:
• Equipment used in data collection
• Survey procedures
- Post processing Accuracy Report
- Image Chip showing GCP location
- Field Station diagram (sketch)
- Digital pictures of the GCP location, from each cardinal direction
- Google Earth KML and ESRI shapefile of GCP
Quality 01 Premium – Accuracy from 1cm/Δ H X 3cm/Δ V to 5cm/Δ H X 5cm/ΔV. With CompassData’s Quality 1 data a customer receives photo identifiable Ground Control Points with Accuracy from 1cm/Δ H X 3cm/Δ V to 5cm/Δ H X 5cm/ΔV.
Quality 01 – Accuracy from 1cm/Δ H X 3cm/Δ V to 10cm/Δ H X 10/ΔV. With CompassData’s Quality 1 Premium data a customer receives photo identifiable Ground Control Points with Accuracy from 1cm/Δ H X 3cm/Δ V to 10cm/Δ H X 10cm/ΔV.
Quality 02 – Accuracy of 20cm/ΔH X 20cm/ΔV or better. With CompassData’s Quality 2 data a customer receives photo identifiable Ground Control Points with an Accuracy of 20cm/ΔH X 20cm/ΔV or better.
Quality 03 – Accuracy of 50cm/ΔH X 75cm/ΔV. With CompassData’s Quality 3 data a customer receives photo identifiable Ground Control Points with an Accuracy of 50cm/ΔH X 75cm/ΔV.
Quality 04 – Accuracy of 70cm/ΔH X 1.25m/ΔV. With CompassData’s Quality 4 data a customer receives photo identifiable Ground Control Points with an Accuracy of 70cm/ΔH X 1.25m/ΔV.
Quality 05 – Accuracy of 2.5m/ΔH X 5m/ΔV. With CompassData’s Quality 5 data a customer receives photo identifiable Ground Control Points with an Accuracy of 2.5m/ΔH X 5m/ΔV.
The World’s Largest Commercially Available Ground Control Points Data Set
CompassData provides complete global coverage, with more than 60,000+ photo-identifiable Ground Control Points available right now, and more GCPs being collected all the time.
The control points residing in the CompassData archive have:
- readily view-able metadata indicating the date of collection
- the positional quality
- additional supporting data including a control point sketch and photographs of the point taken during collection
Data from competitors won’t be perfect, but it will be close. That’s not good enough for CompassData’s Control Freaks. We have the most accurate, precise data in the industry.
Ground Control Applications: Satellite
Satellite data is improving, but the fact is, the vast majority of satellite imagery available today requires Ground Truth to create accurate maps. Orthorectification without GCPs is inherently inaccurate.
Ground Control Applications: Aerial
When planning an aerial data collection effort, a review of the available CompassData control points in the archive may allow for the use of:
- existing control data
- eliminating or reducing the need to send a survey crew into the field
- saving you time and money on your project
Not all points in the archive will be usable in any given photogrammetric project. However, they do provide an independent check against existing data. They can also provide an excellent starting point for troubleshooting any aerial project control issues. Or to provide an initial starting point for image positioning or project layout.
CompassData also provides rapid-response ground control retrieval virtually anywhere in the world at the customers’ desired level of accuracy, and in a timely, cost-effective manner, to supplement Ground Control Points from our archive for their projects.
Ground Control Points with each downloaded deliverables from the CompassData archive include:
• Coordinate File containing Lat/Long/Elevation and Metadata, in either text or spreadsheet format
• Project Report containing information on:
• Equipment used in data collection
• Accuracy Report
• Image Chip showing GCP collection location
• Sketch diagram, hand-drawn by field data collector
• Digital pictures of the GCP location, showing each cardinal direction
We Provide The Most Comprehensive Geospatial Solution For Ground Control Points
These readily available, archive Ground Control Points or GCPs allow you to accurately correct or enhance aerial or satellite imagery and LiDAR data for any mapping project.
More than 50,000 Ground Control Points in the CompassData archive have all passed rigorous quality-control procedures. Most of the points have been collected for customers who have used them in the orthorectification process or subsequent QA to validate accuracy.
Ensure That Your Operation Mapping Investment Provides The Strongest ROI
CompassData has a team of experienced geospatial experts working for your needs producing complex and detailed geospatial multilayer mapping for your operational intelligence in all stages of the production or management process.
Consult CompassData’s team about how you can get more accurate data and bring improvements in the decision making process.
Ground Control Points Archives includes points in North America, Europe, South America, Asia, Africa, Australia, and the Middle East. CompassData maintains its own GNSS survey crews as well as 30 international partners capable of acquiring high-accuracy points anywhere in the world in a matter of weeks.
Before CompassData, there were no standards for commercial Ground Control Points. We were one of the first to create the business model, so we set the standards – almost by default.
Knowledge Base and FAQ: Ground Control Points 101
What are ground control points? Why do they matter? How are they used?
With the growing constellation of commercial earth-observation satellites, there has been an associated growth in the inclusion of spatial data in our everyday lives. Global Positioning Satellite (GNSS) technology is now in our automobiles, wrist watches, and cell phones. It is becoming increasingly tied to image data, be it a picture of the Earth or the front of the restaurant. We can make reservations with our cell phone while stuck in traffic.
Geospatial professionals process the collected images with ground coordinates in order to correctly position the imagery in relation to the Earth with the use of aerial, satellite and ground-based imagery.
To ensure that the image is in the right position and that the correct image of the restaurant comes up on the screen of the onboard navigation system in our car, it is necessary to provide accurate ground coordinates to tighten the accuracy of the overhead imagery.
This is the role of CompassData. We are continually collecting new Ground Control Points (GCPs) across North America and around the world to provide accurate coordinate data to support an increasing variety of applications.
Reliable GCPs are an essential input for precise orthorectification of:
• Remotely sensed imagery
• LiDAR and IFSAR Surface Models
• Image and mapping data quality assessment
• Photogrammetric mapping
• A fundamental building block of Geographic Information System (GIS) development
Bringing the Real World to Remotely Sensed Imagery
In order to be of any use spatially, Airborne and Spaceborne imagery must be referenced to the real world. By recording precise coordinates of photo-identifiable locations within an image, those coordinates form the basis for remapping that image, through the use of robust software such as Esri ArcGIS, into a usable, accurate map image, ideal for a variety of applications and industries.
Without ground control, accuracies for space-borne images are typically 10-50 meters off, based on onboard position and attitude sensors and known orbital parameters.
Once ground control has been applied, those accuracies improve to .5-2 meters or better.
Through the use of ground control and sophisticated terrain modeling techniques, aerial images can be generated into orthophoto maps with sub-foot relative accuracies and absolute accuracies of under 2 feet.
So, contrary to popular belief, higher quality aerial or satellite imagery cannot replace the need for ground control. In fact, GCP collection becomes increasingly more important as image accuracy is required and user expectations increase. Fortunately, collecting ground control is now a much faster, more accurate, and cost-effective process thanks to the use of GNSS technology.
Field Data Collection and Remotely Sensed Ground Control
There are two ways to ensure that Ground Control Points are accurate. One is to have a human being physically at the location of the required control point, who uses GNSS-enabled equipment with mapping or survey grade capabilities, to verify the longitude, latitude, elevation, and position relative to photoidentifiable elements around it (buildings or other unmovable objects).
CompassData has highly trained field data collectors all over the world, continually adding to and updating our archive of off-the-shelf GCPs.
The other way is through Remotely Sensed Ground Control Points (RSGCP) which are now obtainable through a highly sensitive and accurate satellite radar imagery coupled with postprocessing done using our archive of confirmed GCPs across the globe.
For GCPs in very remote or dangerous parts of the world, RSGCPs are now an ideal option.
As GIS/GNSS Tehnology Grows, So will GCP Need An Increase
Just a few years ago, not many people had heard of photogrammetry, GIS imagery, remote sensing, or LiDAR, except geospatial professionals. These terms may still be somewhat rarified, but awareness is growing daily.
The demand for better accuracy will grow as more and more industries and individuals learn about how mapping can improve their business and their lives. Along with accuracy, the requirement for standardized deliverables that can be quickly and easily ingested into GIS databases will rise.
CompassData is at the forefront of this industry and has been since the early 1990s. All of our more than 50,000 Ground Control Points include a complete set of standardized, accurate deliverables. This makes our GCPs not only the largest commercially available data set of control points in the world but also the easiest to use.