<div dir="ltr">First I'd like to say a big thank you to Pat, Eli & Bob for your responses here, and also to Jeff who I originally emailed, and suggested I email this list. Problems of this type clearly are technically soluble, and some, e.g in the military context, which I'd not been thinking about, have been solved. So let's try to redefine what I looking for, and the questions which arise. So:<div>
<br></div><div>1. A process for geotagging images which are sparse in both time and space, but with human expertise on hand.</div><div><br></div><div>I think this differentiates the problem from the Structure from Motion problems linked to, although I note that they include looking at sparse data. It's just that having just the occasional photos and drawings surviving of a location at various points in the past take sparseness to another level. I may be wrong, but there has to be a sparsity threshold beyond which you need to design in the human expert.</div>
<div><br></div><div>For this stage, I think now I was confusing myself by thinking about warping images to maps; more sensible to warp maps to images, so having tentatively tagged an image with a location, direction of view and magnification, then call up a warped version of vector layer map, such as OpenStreetMap, to compare the edges on the image with what you'd expect to see, and adjust the initial estimates for the image geotagging. It wouldn't need to be perfect, just recognisably making sense to the human researcher; it's not as if we want to land a missile on anything with pinpoint accuracy.</div>
<div><br></div><div>An incidental thought here - what does OpenStreetMap do when new roads and buildings come along? Can it be rolled back to how things were? If there's a data structure of that, could that not be extended to how streets looked before anyone thought of OpenStreetMap? If I was trying to locate a historical photo, it could be helpful.<br>
<div><br></div><div>2. A data structure for holding such geotagged images and relating them to other types of entity.</div><div><br></div><div>Thanks to looking videos showing architectural drawing packages (SketchUp) interfacing with Google Earth, in which buildings are considered as an entity type 'component', I think that's the sort of thing I want. I'm thinking of this in the context of how city-scapes change, so that seems natural. Obviously if it was landscapes, components could be water features or other components of the non-built environment. So you'd want a relation to say that an image is of some component - which would have its own geotag, and also some vector data to describe its 3D extension based on the edges obervable - by machine with expert guidance. This would be a many to many relationship.</div>
<div><br></div><div>3. A process to use this data to realise what it would look like if you looked a certain way at a given point in time - so this is where you would warp the images rather than the maps. This also has to be a solved problem - architects and town planners must be doing it every day as they visualise projected developments, and are also able to add texture from existing images. The product I was just looking at in this connection is <a href="http://en.wikipedia.org/wiki/SketchUp">SketchUp</a></div>
<div><br></div><div>4. Making it happen.</div><div><br></div><div>I'm not going to write too much about this, because it would be too vague and conjectural, but any thoughts on what it would take to achieve the above, and additional ideas on the sort of entities who might argue for it and fund it would be appreciated! I'm also thinking about copyright issues ... any thoughts on that welcome too.</div>
<div><br></div><div>Tim</div><div><br></div></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On 1 August 2014 20:01, Pat Tressel <span dir="ltr"><<a href="mailto:ptressel@myuw.net" target="_blank">ptressel@myuw.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Tim --<br><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr"><div style="font-family:arial,sans-serif;font-size:13px">
This is a project idea which seems obvious to me, and one which would so obviously benefit from OSGeo involvement, that I feel someone on this list will know very quickly if anyone is working on it in an open data way. It comes from thinking about the warping which needs to be done to get from an aerial photograph to a map, and extending the thought to what can be done with a very oblique image - such as I might take standing on the ground. Any photo, not just an aerial one, can be considered as a map just waiting to be tagged with scale, projection, geolocation and date. The photo doesn't have to be great quality - perfection is not needed. In fact, if we allow some artistic licence, we could apply the same process to scans of historic prints and paintings.</div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">And if we had a library of such geotagged images, researchers would be able to specify an area and a time range, and search for images whose area of coverage overlapped it taken during the given period. It would be of antiquarian interest - there's an organisation I belong to called the <a href="http://www.topsoc.org/front/index" target="_blank">London Topographical Society </a> which has access to a mind-boggling number of maps, old photos and prints of London - but also to academics in Geography and Town Planning departments. It would also be of commercial interest to developers looking at the planning context for new developments. And I think I've read somewhere of commercial companies - Google, Facebook? - collecting various picture of the same location, e.g. a holiday destination, and using the combined data to produce images with unwanted obstructions eliminated. It has to be possible, so is anyone working on developing an open source library of images so tagged?</div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">Brief background on me; I'm a maths graduate, now approaching retirement, and with interests not only in history, but also urban development, so a project along these lines is something I'd love to get involved with. Although I might dream to doing some coding, that's just not realistic when my skills are more in MS Office applications and VBA. I've also been looking at 'R' and QGIS, and I could get to the point of doing the tagging, except for date stamping, but if there was anyone else further up the learning curves for these, it would be good to link up. I also have a lot of possible contacts with people who might be interested in such a project as users, which would also make a difference.</div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">It seems like such a nice project, so hoping someone can help<br></div></div></blockquote><div><br>
</div></div></div><div>This is a popular area, since it relates to side-scan sonar, side-looking aerial radar, and cameras suspended from drones, which, even if they're intended to be pointing down, rarely are. (It also seems to be somewhat a solved problem, just not open-source -- as you may guess, this has military use.)<br>
<br></div><div>It also comes up in autonomous vehicles, since one wants to infer (for instance) distance of objects from imagery. For both this and georeferencing, sequences of (partly) overlapping images -- video -- are very useful.<br>
</div><div><br>In fact, this subject is under current discussion over on the Humanitarian OpenStreetMap Team mailing list, with the revival of OpenAerialMap. I'd recommend joining up with the folks over there.<br><br>
</div><div>I'm CCing some folks (Stephen Mather, Kate Chapman, Michael Patrick) who are involved with OpenAerialMap and / or OpenStreetMap and georeferencing in general.<br><br></div><div>Some references re. georeferencing imagery (specifically for drones) and related (Michael probably has more):<br>
<br><a href="http://opendronemap.github.io/odm/" target="_blank">http://opendronemap.github.io/odm/</a><br><a href="http://dronemapper.com/" target="_blank">http://dronemapper.com/</a> (commercial image processing service)<br>
<a href="http://flightriot.com/" target="_blank">http://flightriot.com/</a><br>
<a href="http://ccwu.me/vsfm/" target="_blank">http://ccwu.me/vsfm/</a><span class="HOEnZb"><font color="#888888"><br><br></font></span></div><span class="HOEnZb"><font color="#888888"><div>-- Pat<br></div></font></span></div>
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