TP> It was not clear if the OP indeed wants to map pipelines, TP> or was just quoting the pipeline expert for his opinion about TP> surveying methods. the latter. I'm referring to all nodes, not just pipelines & marker. Just used the conversation I had some time ago as an example.
W> Terms !! W> In Metrology (http://en.wikipedia.org/wiki/Metrology) the words W> accuracy, error, etc have specific meaning .. please forgive my ignorance - let the experts decide on a proper term to be eventually used as tag. "dilution" comes to mind, but that's GPS specific, if I'm not mistaken. FV> Even if you collect plenty of GPS traces with no systematic error, these FV> still cannot beat a theodolite triangulation. when specifying "accuracy", the source of the coordinates shouldn't matter. It could be GPS, DGPS, theodolite triangulation, a file provided by officials or companies ... FV> I used estimated_accuracy=* or gps_accuracy=* a couple of times, IMHO, that's the way to go. would recommend against gps_*, see above. also, there should be a distinction between estimated and actual accuracy. FV> but I doubt FV> that it prevents other mappers from moving or even deleting them. Some use FV> editors like Potlatch, so they are not aware of tags. Some do thousands of FV> edits, all of which are validator based "corrections". They do not ask nor FV> think nor look at tags, except at those reported by the validator. software evolves; if such a tag is considered useful and widely used, it may eventually be supported by the developers. of course, there'll always be the black sheep ... FV> Also, there is no clear line between high and low precision data. Should an FV> editor warn when the precision is better than 1m, but ignore a precision of FV> 2m? This all depends on the precision of the new data, which the editor does FV> not know. for starters, I'd begin with a general warning if the precision of the existing node is less or equal than 2m (thats better than what the average consumer receiver can achieve). to draw a line between high and low precision, this article [1] may be helpful. some GPS receivers show the current precision in meters; GPX files contain HDOP/VDOP/PDOP if provided by the receiver. In theory and if provided, when a GPX file is used as source for nodes, precision could be derived from this information (by whatever means). FV> There are no GPS traces for pipeline markes. actually, there are ;-) I just didn't upload mine. but apart from that, pipeline mapping seems to be a few-(wo)men show, therefore it's more likely that pipeline operators may release their (high precision) data [2] before there are enough GPS traces to significantly increase precision via interpolation. cu [1] http://en.wikipedia.org/wiki/Global_Positioning_System (section "Augmentation" f.) [2] https://wiki.openstreetmap.org/wiki/Talk:Proposed_features/PipelineExtension#status_update.2F1 _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
