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gcp position


tell me if we placed gcp in correct position. we placed gcp about 250 meter interval, yellow color represents flight plan, our project is about wideing of road.

the problem is accuracy of level on is better but off road its worst, please give a suggestion


Your drawings match what we recommend in our article about the number and distribution of ground control points (GCPs) in corridor mapping. As mentioned in it, the denser network of ground control points should yield better results. Regarding the number and distribution, it depends on the relative accuracy of the image geolocation, the size and topography of the area, the image content, etc.

However, if you are also interested in accurately reconstructing the neighboring areas, since this road section has to be widened, I would suggest you add some ground control points in the areas next to the road, for a more even distribution. Indeed, the further away a feature is from a ground control point, the less it benefits from the higher absolute accuracy the GCP brings. This is why we recommend to place ground control points near features of interest.

You will find useful information about acquiring ground control points in the field here.

For more information about general and corridor mapping flight plans, check out this article.
For future troubleshooting, the following article might be of interest to you: Corridor Project has Big Errors on the Edges.