john whelan <[email protected]> writes: > It depends on the requirements. I think mapping from Bing imagery is quite > reasonable and that isn't done to 1 cm accuracy.
Sure. mapping from 15 cm imagery that is actually georeferenced properly is 100% fine but it does not work in tree cover. Also actually georeferenced properly is hard to evaluate. MassGIS imagery and RTK line up super well. > However as you point out there are other solutions and I'm not advocating > one specific solution merely that it exists. If there is a requirement > that needs high accuracy then this might work. I didn't mean to criticize the video I didn't watch. I just meant that 10 cm accuracy gets you really high value in mapping, and I don't think going from 10 to 1 helps that much. Also people need to be clear on what datum the reference network is in, and at 1 cm they need to be clear on their local plate motion. North America is moving at about 3 cm/year and some other places are double that. > Perhaps it needs a wiki entry to list the advantages and disadvantages of > different approaches. Certainly locally imagery is much better than GPS > near tall buildings. non-rtk, yes. But imagery is challenged if the height models are off, because it is slant and reduced to be apparently vertical. Unfortunately all of this is pretty hard. > Another issue is if you have two things in the map one that has been mapped > with high accuracy and one not there isn't really anyway to tell which is > the high accuracy one. True. We need accuracy metadata on coordinates; I put "RTK GNSS" in my changeset comments when that's how it is. _______________________________________________ talk mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk
