On Sun, May 17, 2009 at 11:32 PM, MP <singular...@gmail.com> wrote: >> http://en.wikipedia.org/wiki/TopSat >> http://www.qinetiq.com/home/defence/defence_solutions/space/topsat.html >> >> Apparently you can rent it for £25k a week... easily within the ambition of >> donate.openstreetmap.org. > > How large part of earth could be imaged in that timeframe? > Topsat have 2.5m resolution, which is quite fine for most areas, > though less than aerial imagery ...
2.5m sounds about the same as Y!, so its even enough for rudimentary building mapping. but thats the black-and-white figure, the colour resolution is about 5m. :-) out of interest, is there a link to the £25k figure? i couldn't find any pricing information on the net anywhere... i guess hiring it for any fixed period is a bit hit-and-miss, since satellite imagery will be affected much more by cloud conditions. >> MP's point about what you do with the vast quantities of data that you get >> is well-observed, of course. But we like a challenge. > > One thing is having the data on ground - entire world (510,072,000 > km²) from Topsat in 2.5m resolution will have ~ 245Tb of uncompressed > data (you'll get to about 1/3 of that if you discard imagery with just > sea), which is lot, but perhaps still manageable. at 5m in colour, thats about 20.4 Tb for the land portions of the world. compressing in JPEG, which compresses about 2:1 based on their sample images, thats 10.2 Tb - or 1,400 gmail accounts ;-) or it would cost $20,110 to put it into S3 and host for a year (without downloading) or about £1,400 to stick it on some 1Tb SATA drives in a RAID1+0... (interesting co-incidence which implies that each gmail account at capacity costs google about £1 in storage...) > But you have to > either store some non-trivial part of it on the satellite (that is not > as easy as on earth where you can buy some server with RAID and plug > it into wall) while the satellite does not have direct visibility of > the earth contyrol center where it can relay stored images (and then > you have some means to transmit large amount of the data while the > satellite flies over the earth control center) or have multiple ground > stations or bunch of another satellites that relay the continuously > transmitted data. i have to assume that qinetiq have some way of solving this. also, would it be worth it as a PR stunt for qinetiq to just use up whatever spare capacity they have when maneuvering or between clients and give us whatever gets photographed...? anyone know anyone at qinetiq? cheers, matt _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
