In regard to administrative boundaries being attached to other features such as waterways and roads, I think it is a trade-off between accuracy and convenience.
I am most familiar with NSW. Boundaries are not "defined" by words but rather by surveyors' charts. The surveyors may often have been directed to use waterways, roads, mountain ridges and similar features for their surveys. However the waterways and roads have sometimes/often moved but the boundaries have not. Words are sometimes used to describe boundaries such as "it follows the river and then goes south along the main road ... " Such a description is approximate and is near enough for many purposes, especially if one's area of interest is well within the boundaries. However it may not be sufficiently precise if one is concerned with particular locations close to the boundaries. Examples in NSW that might be considered include the boundary on the Murray River west of Tocumwal, the Lachlan River east of Cobb Highway, Willandra Creek south of Roto, Bogan River at Girilambone. If the boundaries were attached to the respective waterways, either the boundaries or the waterways would be incorrect. Where boundaries are mapped on rivers or roads, mappers may re-align the river or road as changes occur and the administraitve boundary becomes distorted, sometimes only slightly but usually increasingly significant over time. Alternatively we could map the waterway or road using the administrative boundary data (as some mappers have done in the past) and ignore the satellite imagery and GPS data but this affects the accuracy of the location of the waterway or road. While I will accept the community's group decision, personally I think accuracy is to be valued over convenience. I strongly advocate for accuracy by mapping administrative boundaries separate from other features on the map, even if they are nearby. The decision in regard to the above issue will affect use of a source tag for the boundary. If the boundary is an approximation and attached to waterways or roads then it would be incorrect to use a boundary source tag, However if boundaries are mapped separately and accurately, then we should record the source of the boundary data. While I would suggest adding the source tag to the relation for the administrative boundary, it might also be added to the way if there is any need to specify the source for the way e.g. if using the administrative boundary for the geography of a river, then also give the source of the boundary data as the source for the waterway. _______________________________________________ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
