![]() ![]() Skipping ground control points may yield perfectly fine results, but your reconstruction might not have the correct scale, orientation, or absolute position information. If your drone is not RTK enabled, then we will always recommend using GCPs. If you are using an RTK drone, then our tests have found ground control points do not meaningfully improve accuracy. GCPs have been a traditional part of aerial mapping projects. Ground control 2 how to#Pix4D documentation has detailed and up-to-date information about how to include GCPs in your project.ĭo I always need to use ground control points? You’ve placed GCPs in the field, marked them accurately, and flown your survey - what’s the next step? This large project used 160 GCPs and tie points. The surveyors are marking the corner, not the center of the L. Small in relation to a building, but the 'center' is unclear compared to a traditional GCP. Imagine a line of spray paint: it might cover a handbreadths of the site. The jury’s still out on whether or not this is better than nothing. Mappers in a hurry sometimes slash an X on the ground with spray paint to use as a GCP. Hand painted ground control points: sacrificing accuracy for speed External tests show there’s generally no need to place dozens of ground control points: aim for between 5 and 10.If the area isn’t perfectly flat, place GCPs across the different elevations - at the top and bottom of a hill, for example.Shadows are tempting - but they may move even in the time it takes to fly a site. Some features (such as parking spaces or the corner of buildings) may be too repetitive to be useful. Be careful when choosing ‘naturally occuring’ ground control points.Ground control points should be on the ground for consistent results. These quick tips will help you place ground control points for better accuracy. The ideal layout for ground control points. Ground control 2 manual#Our users have made ground control points out of concrete posts (because painted GCPs kept getting washed away in the rain), vinyl flooring, baseball bases, and cardboard.Ī team of Pix4Ders baked cookie GCPs to test this theory - they worked well as manual tie points, but because we didn’t know the precise coordinates we can’t say the model was correctly georeferenced. ![]() It is better to use water-proof materials if you plan to use them again, and use a matte finish to reduce glare and improve visibility. The go-to rule is to use high-contrast colors - which is why ground control points are usually black and white - and be sure that they are large enough to be identified from your particular flight altitude. There are many ways to make your own ground control points and in theory, GCPs can be made out of anything. Even if this is not sufficient for a surveyor, it can be useful for projects which need to be overlaid on a Google Map. One study found that accuracy varied from 0.1 meter to 2.7 meters. The accuracy of Google Earth coordinates is variable at best. ![]()
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