Slowly I start seeing where this goes. If I figure rightly, OSM has gained permission to use the french cadastre data under certain conditions. So this is a mass data job! I thought you might just want to do some OSMing maybe on your own home town, but this seems to be a major project and large quantities of data, like the older Ordonance Survey maps in Britain. Big thumbs up to the french authorities for letting you use the data. It looks like there has been a great effort done on the data already, with hundreds of thousands of individual maps already vectorised. Is that so? And how did they do it? This is the information I'm refering to (sorry, my french is a bit rusty, so I'm not 100% certain if I interpret this correctly):
http://wiki.openstreetmap.org/wiki/WikiProject_France/Cadastre On 7 Dez., 12:03, Olivier Croquette <[email protected]> wrote: > Actually the scale strongly varies among the 24 pieces (maybe not in > the sample I provided though), so I have Z factors. One of my problems > is to convert this Z factor into a scaling factor (see the message > about the transX/Y/Z parameters). The data being from an official source, hey, even the cadastre, I reckon their scales are correct. Like the images you posted are 1:2000. I think it best to bring them all to a uniform scale before putting them into hugin - they are all supposed to end up at the same scale anyway. The smaller the number of parameters you have to deal with, the better - and scaling can be done very accurately with other tools. I would like to give you a good answer about how to convert a scale into a Z parameter, but the connection is non-obvious. It is certainly not as straightforward as linear distances along the optical axis. I'll try and find it out, though. > > Stitching this, with the input images' projection and the panorama > > projection set to rectilinear, should give you a result where the > > input images aren't distorted at all, just nudged into place. > > Yes, it works, but the process doesn't scale (because of the memory > and the required manual steps). Now I'm not sure if I understand where this is going. My understanding of OSM is that the project's aim is to create a vector map of the earth. Vectorization is done piecemeal, so I don't see why you need very large raster maps. Hugin is well capable of dealing with large images (I'm not sure what the actual limit is, but I suspect it's beyond anyone's memory), but you wouldn't want to vectorize from a gigapixel map. Why first create one and then chop it into tiles if you can create a set of maps each of resonable size (like some 100 MBs) and use those as backdrop for vectorisation? > The cadastre is reference for the property limits, so it's very > accurate. I could verify that myself by stitching myself a few > samples. They fit very well. Okay, granted. Just keep in mind the error sources. I don't know how accurately you can georefernce with JOSM, since I'm a QGIS user... > > To use the data as source for OSM, I think you'd be > > well advised not to stitch the maps with hugin, but to georeference > > the individual sheets as best as you can, be it in JOSM or QGIS. > > That was actually my first approach, but since I don't have precise > sources for the georefencing, it's not accurate enough. That's the > reason why I am trying to use the internal consistency of the pieces > between each other. The data look to me as if they had precise grid references. I'd assume it doesn't get better than that, please correct me if I'm wrong. If you know the projection, the grid crossing points that are marked on the map should be perfect for georeferencing the sheets. Are you sure you are using the proper projection for the map data? What is the projection, by the way? And - do have a look at QGIS: with QGIS georeferencing raster data in about any projection is simple. All you need is the projection and a couple of points, like the grid intersections; it's a point-and-click operation. It is fully integrated with OSM via a plugin and it's free, so you can just play with it a bit to see it. I'm not sure if JOSM does the same so easily. You can even work on the raster data in their original projection; the vector layers are reprojected on-the-fly, so they can be in OSM's WGS 84 but will still show correctly on the cadastre sheets, keeping the substrate as legible as possible to aid the vectorization. with regards Kay -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hugin-ptx
