GCP Distribution in the Survey Area
This article will describe the best practices for marking and measuring Ground Control Points based on the area to be measured.
For rectangular areas of interest, we recommend that a minimum of 5 ground control points are placed every 400 feet for non-RTK flights and every 1000 feet for RTK flights. This would place a control point in each corner and one near the center. The absolute minimum of control points is 3.
For highway projects, we recommend a ground control points is placed on each side of the highway project, 400 feet apart for non-RTK flights and 1000 feet for RTK flights. The control on each side of the highway should be offset and placed on each side of the highway. This will ensure that both sides of the highway have ideal coverage. For RTK flights these distances can be increased to 1000 feet.
GCP Distribution for elongated areas
Ground control points spreading recommendation in relation to desired topographic mapping scale for elongated projects:
|
Num. |
Map Scale |
2 GCP in both project side in each DL or DW [m] |
Accuracies in MSE in 95% [cm] |
Pixel foot print [cm] |
|
1 |
1:250 |
50.0 |
± 12 |
2.5 |
|
2 |
1:500 |
100.0 |
± 25 |
5.0 |
|
3 |
1:1250 |
250.0 |
± 30 |
12.5 |
|
4 |
1:2500 |
500.0 |
± 40 |
25.0 |
|
5 |
1:5000 |
1000.0 |
± 80 |
50.0 |
|
6 |
1:10,000 |
2000.0 |
± 120 |
100.0 |
GCP Distribution for polygonal areas
Ground control points distribution recommendation in relation to desired topographic mapping scale for polygonal (area) projects:
|
Num. |
Map Scale |
1 GCP in each square DL X DL in [m] |
Accuracies in MSE in 95% [cm] |
Pixel foot print [cm] |
|
1 |
1:250 |
50.0 |
± 12 |
2.5 |
|
2 |
1:500 |
100.0 |
± 25 |
5.0 |
|
3 |
1:1250 |
250.0 |
± 30 |
12.5 |
|
4 |
1:2500 |
500.0 |
± 40 |
25.0 |
|
5 |
1:5000 |
1000.0 |
± 80 |
50.0 |
|
6 |
1:10,000 |
2000.0 |
± 120 |
100.0 |
- Convex hull polygon consisting of GCP’s must cover the entire ROI circumference.
- User must add one control point in each DLxDL.
Related Articles
GCP Accuracy
Ground Control Points (GCP) Accuracies Measuring precise ground control point is very essential to getting a precise 3D model. Below are some recommendation as to how to select and measure GCP"s Accurately measure the position and elevation of the ...Marking the Ground Control Points (GCP's) Manually
This article covers all the process of marking GCP's on images. This is needed for all flight instances that were marked as needing manual GCP's at upload time. After the upload and the the link process are done, the site will appear as “Pending GCP ...AI Assisted Ground Control Points (GCP's) Marking
Machine (ML) / Artificial Intelligence (AI) can be used for marking GCP on images by looking for different shapes of marks in the images. The search of these marks in images starts initially by using the GPS location of the images and using a ...Automatic Georeferencing (AGR) Best Practices
Automatic Georeferencing capability is based primarily upon the ability to match features in images between two flight instances surveying the same site. In order to filter out false positives, the matching criteria are very strict. For this reason, ...Tips and Tricks for Using Local Coordinate System (LCS)
When using LCS, DatuBIM automatically brings the GCP’s to the approximate area where the images are. Beyond that, it is the user’s responsibility to bring the GCP’s to the exact location to allow for marking them on images. In all cases, the goal is ...