Nice article over at the BBC on new US Army drones. Helicopter based for VTOL, they sport a 1.8GP (yes, thats gigapixel) video camera capable of real time video feed at 10 frames per second, allowing multiple target tracking up to altitudes of 6000m. Nice.
Well just about…. Beidou is the Chinese GPS equivalent and is now “operational”. Well its got 10 operational satellites and these will provide coverage for China and near-surrounds. Expect global coverage by 2020. Whilst perhaps uptake won’t be quick, it is designed to be inter-operable and expect to see handsets starting to take advantage of US, Russian, European and Chinese satellites for positioning. An exciting marketplace at the moment….
I’ve moaned before about the price of Kindle books and that they are often pennies cheaper than the printed version…. and you can’t lend them! Anyway, part of the reason is that VAT is charged on ebooks, but not on paper books. As PCPro explain, a cut in VAT on ebooks in Luxembourg may well see some sort of parity across Europe and we deserved dropped in prices.
Capturing aerial imagery from KAP can be a hit and miss affair (although far less so with digital cameras) and therefore setting the camera up carefully prior to imaging is essential. For oblique images there are fewer problems because there is a lot of light coming in to the camera and you can utilise whatever shutter speed/aperture you want. That’s not to say its not without problems, but that automatic camera settings can often get great shots.
When you’re trying to obtain straight verticals from KAP in order to generate DEMs (see my paper) then things become more difficult. It reminds me of a more general quote from my undergraduate days (thanks Lindsay):
"In aerial survey we have to take a large number of photographs to a set plan, from a moving platform, at a great height and at a low temperature. Alone or collectively these conditions are foreign to most photography. Despite this the photogrammetrist requires excellent definition of a low contrast object, further reduced by poor atmospheric conditions."
Which about sums things up….. OK, its not quite as severe from a kite, but the requirements for high definition photos of a low contrast object remain the same. This is even more so when we consider that we want to collect stereo imagery: the photos need to be good. So when it comes to the camera how do we actually set it up?? My paper linked above has the following paragraph in it:
"The photogrammetric use of aerial imagery requires sharp definition and this is controlled on the camera by focus, shutter speed, aperture and ISO settings. With flying heights in excess of 50m, a focus setting of infinity is used. The focus ring is normally taped and auto-focus setting switched off, this eradicates changes to the focal length during the flight. As the kite is usually moving during image capture, fast shutter speeds are needed. Field tests suggest speeds in excess of 1/500 s are required. In addition an aperture of at least F8 (for a wide angle DSLR) is preferable, to allow sufficient light to enter the camera system whilst minimizing lens distortions. In most field situations an ISO setting of at least 400 is necessary for normal UK daylight conditions. With automatic digital cameras, these stipulations mean that the ISO is set prior to image capture with the camera in 'aperture priority' mode. Prior testing may be required in order to ensure shutter speeds are fast enough."
So there we have it: tape the focal ring at infinity, put the camera in aperture priority and maintain an aperture of at least F8. The camera will auto-set the shutter speed but we actually need speeds in excess of 1/500s. This can be problematic as the only light entering the camera is reflected off the Earth’s surface and for low reflectance features (e.g. vegetation) this can be quite low. One thing I didn’t explore in the original paper was the AutoISO feature that is available on the D70 and pretty much every Nikon DSLR since. Yes, it automatically sets the ISO for you and there is a nice layman’s article here. Nikon Support also offer some sage advice. In short though, AutoISO increases the ISO speed (aka sensitivity) of the sensor in order to expose the photo correctly. The brilliant aspect when shooting in aperture priority is that you can set the threshold shutter speed at which it should kick in. So in our case we could specify 1/500s to always make sure photos are sharp.
This is no panacea though… yes it effectively adds 3 or so f-stops but you increase the noise in the image, particularly once you get over 1000. And whilst we want sharp photos for photogrammetry, noise won’t help things. Clearly some more experimentation needed here, but AutoISO is well worth enabling.
We also mustn’t forget the ambient atmospheric conditions at the time of image capture. We want sun… yes, but more than that we want texture in the image. If we are interested in enhancing topography then shadows are helpful. A low angled sun can significantly improve texture but again you lose sunlight which affects exposure. Its a careful balance which you rarely get right all the time!
P.S. And don’t forget to turn the auto-shut off to the longest possible time. You don’t want the camera to power down after 30 s!!
NASAs Earth Observatory have posted the first global image from VIIRS on NPP. This is a great start to demonstrate the capabilities of VIIRS; and for those doing introductory courses in remote sensing the accompanying notes nicely explain why we have sun-synchronous orbits and why there is variation in the imaging of the global composite.
“The government has signalled a revolution in scientific publishing by throwing its weight behind the idea that all publicly funded scientific research must be published in open-access journals.”
which is verging on the side of sensationalist, but does reflect a genuine interest by government to become more transparent and make outputs of funded research more widely available. I am a big supporter of open-access as it allows all to access research work, but as The Guardian notes, journals add significant value through peer-review and the actual publication. Someone as to do this and it has to be funded. They note the physics research community moving funding from subscription to author-pays (something we used at JoM), but consensus varies by discipline. The actual cost of publishing a journal article is quite high (somewhere over $1000) and for many disciplines with very low amounts of research funding this is not sustainable. And it begs the question about where to publish non-funded research (again, varying by discipline, and often in very significant quantities).
So if the author doesn’t pay and the library doesn’t pay, who does? Well that’s a good question and why the subscription model remains the most popular as it is the closest solution. Many open access journals are directly funded by learned societies who also have subscription based journals, whilst learned societies also rely upon journal subscriptions to fund research activities. I don’t know what the mix between commercial and learned societies is, but it would be interesting to investigate. I don’t think anyone would argue with reducing excessive profits by some publishers, but there has to be a publishing solution in place that is fit-for-purpose.
Some of you may know that I’m a big fan of Carbonite, the online backup facility. Yes it charges, but for unlimited storage and a real no-hassle backup it is a bargain at $59. Which in my book is pretty good for the 85Gb I’ve got stored there. Whilst it’s really billed as online backup, it is a “webdrive” and the web interface to access files is pretty reasonable. Of course, there is also now an Android app to do this which is simple, small and fully functional. Very handy to be able to grab a file whilst out and about.
Nice article at The Guardian on using a data contract on your mobile to route all your comms traffic. The introduction fails miserably in what is mean to be a newspaper article… you know what they say, don’t bury the lead! Well they have here. Anyway, given everything is digital, all the mobile operators essentially provide is a data pipe, quite what you put through it is irrelevant and the fairest option is to charge by the Mb. Of course many of the profits come from calls and roaming, so operators are keen to keep this nice top slice.
But the market is changing and what Skype/IM did on the PC is now happening on the mobile through apps like WhatsApp which is available across all smartphone OSes. This is the way the market is headed, although the gotcha is that to use such a service your friends need to be on it as well, although they can also operate as gateways to traditional voice and txt services (for a price!). Skype succeeded by being first to market so its an area to watch closely (and, worth noting it might well be against your contract T&Cs).
Loads of stuff is sent, received and archived as PDF. Its a great format originally derived from postscript (by Adobe) designed for bridging the gap between designing a print job on a PC and delivering it to a printer for output. Since then it has evolved considerably to include audio, video, 3D, layers, meta-data, digital signing and form filling to name a few. And since Adobe opened the format up there have been many vendors providing PDF readers, writers and editors. Obviously Adobe has its flagship product Acrobat, but Foxit remains my favourite for small footprint, rapid rendering.
In terms of writing files there are a few open variants that are worth considering:
FreePDF-XP: if you can get past the impenetrable German download page, this is a very capable and useful product. DoPDF: nicely configurable PDF printer driver. Plenty of options, way over and above the simplistic PDF export in MS Office.
If you fancy a nice combination then FinePrint allows you to accumulate and edit print jobs, whilst PDF Factory produces the output. Paid for, but excellent apps.
I’m currently involved in a project led by Paolo Paron (UNESCO-IHE) looking at beach development in the Netherlands. This is really a proof-of-concept project and follows on from the earlier training day back in October where we ran through a full kite aerial photography setup. During that day we had temperatures that peaked at 20oC…. amazing for October!
Anyway, the return trip to the Netherlands was to see the full kit that Paolo had assembled and take it to the field site for full testing/tweaking. The Netherlands is renowned for its flatness and by that I mean: bikes and wind. There were plenty of the former in evidence….. and none of the latter!!! Well, almost. It was the week of dense fog which virtually shut Amsterdam airport, however EasyJet flights in to Schiphol were almost unaffected. A remarkable effort. It was my first visit to the Netherlands and I must say, yes, it’s flat but also that the public transport system is regular, reliable and well used. Bikes are everywhere and it’s clearly a mode of transit favoured by all ages and types. Streets are wide and there are many segregated bike ways, in addition to the onus being on the driver. All in all very civilized.
Paolo (and Niels Anders, a PhD student at Amsterdam who has spent time at Kingston, and a “sixth form” student on work experience) met me at Den Haag HS railway station and from there we went out to the coast. The pictures say it all really: incredibly dense fog and winds <3 kph. Yes, that is a kite flying but t was hard enough to just get the thing off the ground let alone fly anything from it. Paolo did fully assemble the rig and camera, even though we couldn’t fly it. He has bought most of the bits from the highly recommended KAPshop and is testing one of their self-levelling rigs. He also has a Nikon D7000 which is the successor to the D70s, 80s and 90s I have used. At the moment he has a manual 20mm lens which will be interesting to see the results of the test field imagery from (in comparison to our auto-24mm).
So all in all it was disappointing not to have a full flight test, but immensely useful in fully ground testing the kit and ironing out some niggles that needed fixing in the setup. Watch this space for further results.