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Posts Tagged ‘KAP Rig’

Nokia N8 PUSH

Posted by Tom Benedict on 24/11/2010

Some months ago Nokia put out a call for proposals for how to use a KAP rig based around a pair of N8 phones.  At the time I’d been doing some KAP with a photographer in Kona with the goal of photographing whales in the ocean.  So I had whales at the front of my mind.  It wasn’t too much of a stretch to come up with an idea that involved doing KAP of whales.  I sent the idea in, but didn’t really expect to move forward with it.

Turns out I was wrong.  My idea was selected, and not long ago I was contacted by the N8 PUSH team to let me know.

??!  !!!  COOL!

There were some questions to answer and some details to be worked out, but everything came out ok and in the end I was given the timeline and was told to expect a package in the mail.  There’s no curbside delivery where I live, so I’ve been swinging by the post office to check out my PO box ever since.  Nothing yet, but it’s getting clooose!

The package should contain two Nokia N8 cameras, each sporting a 12MP camera with a fixed focal length Carl Zeiss lens, along with a KAP rig designed specifically for the N8, and a kite.  The two phones come loaded with the N8 KAP application, which allows the KAP rig to be controlled from the phone on the ground, and for the aerial phone to stream its video signal to the ground phone.  All in all a seriously cool setup!  I was a little skeptical of the camera at first, but hearing the Zeiss name and seeing a video clip of the camera focusing (yes, it actually focuses) went a long way toward laying those concerns to rest.  What finally did my concerns in was seeing a set of KAP images made by Ricardo Ferreira with the N8 phone.  The image quality was better than most point and shoot cameras, and worlds better than any phone camera I’d ever seen.  (For anyone who’s not familiar with KAP and with the KAP-Nokia connection in particular, Ricardo is an excellent KAPer, and developed the first Nokia KAP rig, based around the N900 phones.)

Operationally, this will be a significant change from the way I’m used to working in the field.  I don’t have a video downlink on my current rig.  The N8 rig does.  I can do movies with my current rig, but I tend not to.  In any case 640×480 is as good as I can get with my current camera.  The N8 does 720p HD video. Right now I don’t have any way to get GPS information for where my camera is in space.  Yeah, I can add a GPS photo tracker to my rig, and probably will in the not so distant future.  But the N8 phone has GPS built in, of course.  I just hope the EXIF headers on the files include the GPS information.  Even the rig itself is different.  I’m used to plugging in cables, screwing down cameras, attaching safety lanyards, and the like.  To use the N8 rig, you snap the phone into the rig and you’re done.  From what I’ve gathered, the aerial phone controls the rig via a Bluetooth connection.  No wires, no screws, no nothing.  And no legs!  The rig has no legs.  But the way it’s shaped, it really doesn’t need them.

So in addition to the PUSH project itself, I’m interested in seeing how the N8 rig behaves in the field.  I’m planning to give it a thorough shake-down and post a review here and on the KAP forums.  Luckily, there’s still some time before the whales come through the Hawaiian Islands.  So I’ve been picking out some likely flying spots where I can put it through its paces and see what it’s got under the hood.  High on the list are Kiholo Bay and Puako.  I’d love to give it a try at the summit of Mauna Kea, but cell phone signals really do mess with the radio telescopes up there.  So it’s a no-no.  Waipio Valley and Pololu Valley are also high on the list since they offer some of the more challenging wind conditions for doing KAP on the Big Island.  (Besides, on the drive back from Pololu there’s a fantastic deli in Hawi called Lighthouse Delicatessen.  Can’t beat a KAP session that ends with a great lunch!)

By the end of the land-based sessions, I should have a better feel for how the rig handles, I’ll have some seat time with it on a couple of different kites, and I’ll be ready to trust myself to launch it off the back of a boat.

Now all we need is whales!

– Tom

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Posted in Hawaii, Kite Aerial Photography, N8 Push, Photography | Tagged: , , , , , , , , , | Leave a Comment »

Challenging but Rewarding

Posted by Tom Benedict on 17/11/2010

I recently had a pair of flights that yielded really nice results.  The first was done just on a whim.  In the past I’ve flown at Mala`ai, the culinary garden at Waimea Middle School in Kamuela, Hawaii.  I like flying there for a number of reasons.  It’s a pleasant place to fly with no ground hazards or obstructions, it’s a great place to try out new ideas for orthoimaging, it’s an interesting subject, and the school uses the images to help plan future work in the garden.  One of the coolest things about the garden is that it’s largely the students who do the planning and the work.  And boy do they ever move FAST!  I’ve never photographed it twice and seen the same thing.  It’s constantly changing.

But almost every time I’ve flown there, I’ve underestimated the size of the place!  The field of view on my camera’s lens is such that the field of view on the ground in the horizontal direction is almost exactly the same as its altitude.  This helps me compose shots when doing orthoimaging.  But vertically the field of view is smaller, and in the past I’ve clipped.  This time was going to be different!  I’d fly high enough to get the whole thing in one shot!

And in the end I did:

Mala`ai - The Culinary Garden at Waimea Middle School - 11 November, 2010

This is still a composite image because I wanted to be able to rotate it to line it up better with the edges of the frame.  But there are no stitch errors inside the garden that needed attention.  The garden itself came from a single image.  As soon as I’d processed the image I let the folks at the garden know there was a new image to download.

About a week and a half ago I got a call to ask if I could photograph the Anuenue Playground in Kamuela, as well.  I’ve wanted to photograph the playground for years, but there are a number of ground hazards and obstructions that have made it less than ideal.  Even though the adjoining football/baseball field doesn’t have lights any more, the poles that used to support them are still there.  There are large trees near the park.  It’s bordered on two sides by busy roadways.  And worst of all the park is full of kids!  I have never had a rig fall off my kite line, but that doesn’t mean I don’t believe it can.  So a great deal of additional paranoia was called for.

I surveyed the place a couple of times that week, trying to find a good angle to launch and approach the park.  But depending on the direction of the wind I could add above ground high voltage power lines to the list of ground hazards.  No thank you!  It looked like the only reasonably safe approach was for the wind to blow out of the west-northwest, and for it to be super-steady.  I didn’t even bother to call back to let them know.  I felt like a failure.

Two days after I made the garden picture, I checked the wind models.  Lo and behold, the afternoon called for soft and steady winds out of the west-northwest!  Sure ’nuff, by 2:00pm the winds had shifted and the conditions were ideal.  I waited out an event that was happening in the football field, my chosen launch spot, but by 3:30pm the coast was clear.  I put up my Fled, put my camera in my ortho rig, and got it in position.

There’s one other piece of KAP gear that figures prominently into this session: my son.  I knew I’d never spot it on my own, so I asked him to grab his walkie talkies and come with me to the park.  He got on the radio and guided me in, and I checked my apparent altitude against the footprint of the park on the ground to make sure I had the field of view to get everything.

I came close.  There’s one apparatus in the park that didn’t make it into the photo set, but the rest of the park did:

Anuenue Park, Waimea

I didn’t get enough overlap for a clean crop, but it covered the bulk of the park with reasonably sharp detail.  A quick pass through PTLens to take out barrel distortion and a small amount of tilt, and then a pass through ICE to make the composite, and the image was done.

All in all the camera was in the air for only 14 minutes, taking pictures every five seconds.  The resulting set of images offered a rich selection to work from.  I feel confident that as the restoration work on the park progresses, I’ll be able to return and make additional documentation photos for them.

Can’t beat a good day.

– Tom

Posted in Hawaii, Kite, Kite Aerial Photography, Photography, Weather | Tagged: , , , , , , , , | Leave a Comment »

Panorama Workflow

Posted by Tom Benedict on 23/07/2010

I’ve had some opportunities to play with my camera on the ground as well as in the air, and to test a number of image sets on the software I’ve been using.  Two days ago my wife and I took our kids to Pololu Valley to go hiking.  On the off-chance the weather would be nice, I brought my KAP gear.  The weather was fantastic, with solid winds for kite flying, and beautiful partly-cloudy skies.  Time to play!

I ran about 5GB of images through the camera from various vantage points.  In creating the base images I tried to incorporate everything I had learned from the earlier experiments.  The resulting photographs turned out quite well, so I’m considering the new workflow to be a win.  I’m sharing it here in the hopes that someone else doing kite aerial photography will give it a try and take it even further.  Here are the details:

  • If you can shoot RAW, shoot RAW.  I can’t, but in the near future I’ll be able to.
  • Use Manual Exposure mode on your camera.  Set it on the ground, check it, and double-check the histograms to make sure you’re getting bullseye exposures.
  • Use at least 1/1000 second exposure speed.  I’m using 1/1250.
  • Use the slowest ISO setting you can to control noise.  This is of less concern with a DSLR, but every bit helps.  I made this set at ISO 80.
  • Use the sweet-spot aperture on your lens if possible.  My lens is sharpest around f/4 to f/5.  I couldn’t use this aperture and hold the other numbers, so my lens is wider than ideal.  But the benefits in noise at ISO 80 make this a reasonable choice.  I give up some sharpness for lower noise, and keep the fast exposure speed to avoid blur.

Once the camera is in the air, all my panoramas were made with the camera vertical.  With a KAP rig this either means building the rig around a vertical camera (Brooxes BEAK rig), or using an L-bracket on a conventional rig, or having a dedicated Horizontal/Vertical axis on the rig.  I recently modified my rig to add the HoVer axis, so this is the route I went.

The idea with this technique is to start the rig on a slow spin, and to trigger the shutter continuously.  This technique was developed by a French KAPer who goes by the name of Vertigo on the KAP forums.  With a sufficiently fast shutter speed, this works perfectly.  My A650IS does one frame every 1.1 seconds.  With a 10-second-per-rev rotation rate, this works out about perfectly.  I’m upgrading to a Canon EOS T2i DSLR in the near future, which has a much faster frame rate.  I’m planning to build an electronic release cable for this camera that will give me the same 1-frame-per-second rate my A650IS has so I can continue to use this technique.

  • Start the rig rotating at a rate that gives you adequate overlap between images, and minimizes motion blur from the rotation, given the camera’s shutter speed.
  • Once the camera is rotating cleanly (no see-sawing on rotation, no jerkiness in the pan axis, no swinging around, etc.) trip the shutter.
  • Make at least two complete orbits of the camera, tripping the shutter non-stop the entire time.  This is for a couple of reasons:  First, it gives you plenty of frames to choose from in case one is blurry.  Next, it gives you a range of random tilt angles that you can use to fill in gaps later on.  Finally, if the rig starts to move, the second orbit will still produce a clean panorama.
  • If you want to make a larger panorama, change the tilt after two orbits and make two more orbits at the new tilt value.
  • While all of this is going on, do everything you can to minimize camera motion.

This should produce a nice set of images from which to work.  You may well end up using them all, so don’t toss any of them!

I use Autopano Pro for stitching.  Some of the tricks I’ve picked up will apply to other packages.  But if you find yourself scratching your head and thinking, “No, I’ve never seen that,” don’t sweat it.  Your software is different.  Skip that part.

One of the first problems I ran into is that Autopano Pro deals really well with point features, but not very well at all with linear features.  For example, it’ll match up individual stones on a beach like a champ, but it will produce lousy horizons if the horizon is just water and sky.  It makes no effort whatsoever to correct for lens distortions if the bulk of the picture is water and sky.

The fix I found was to use PTLens to correct lens distortions before using Autopano Pro.  PTLens is a $25 plug-in for Photoshop.  Even better, it’ll run as a stand-alone program and will batch process hundreds or even thousands of images at once.  If you’ve got a block of images you photographed as fodder for panorama stitching software, it’s no problem at all to batch process them all to remove lens distortions.  Water horizons should now be ramrod-straight lines across the frame.

So back to the process:

  • Run the entire image set through PTLens to remove barrel distortion, vignetting, and chromatic aberrations, but nothing else.
  • Process the images with Autopano Pro, or the panorama software of your choice.
  • Do everything you can to get completely horizontal, completely straight horizons for water.  Nothing kills a pano faster than a grossly errant horizon.
  • Save as 16-bit TIFF images.  16-bit workflow can be a real PITA, especially on a smaller machine, but it hides a lot of ills when it comes to large-scale processing like Levels and Curves.

At this point I open up the images in Photoshop.  I’m still using Photoshop 7.  I’ll upgrade to CS5 as soon as I can afford it.  But for now it still does everything I need.  Want is a whole ‘nuther story, but as far as my needs go, it’s fine.

  • View 100% and check for stitching errors.  Repair all of these with the rubber stamp or heal tools.
  • If your kite line shows up in the image, remove it using the same tools.
  • If you cropped your panorama wide enough to have gaps in ground or sky, open up all the images that went into the panorama, as well as the second orbit you made from that same location.  Use the rubber stamp tool to pull patches from any and all of the input images to repair problems on the panorama.  (This is one of the best reasons to make a second orbit!)  Since you used a fixed exposure, you should be able to rubber-stamp these into the panorama with no changes necessary.
  • Once the panorama is defect-free, look at your levels.  If you did your job setting the manual exposure on the ground, the exposure should be dead-nuts on, or need very little tweaking.
  • Do all your dodging and burning at this point to get the exposure just the way you want.  This can involve lots and lots of time, depending on how meticulous you are with your exposures.  If you’re the kind of person who got into photography in the days of film, and spent your afternoons in the positive darkroom dodging and burning the same negative over and over and over, you may be on this step for a while…

At this point the bulk of the workflow is complete.  But I would advise you not to stop here.  In Photoshop under the File menu is a command called File Info.  Click it.  It lets you edit the header information associated with your image.  At the very least I would fill out:

  • Title – What is the name of the original file on your computer?  Leave out the extension since that can change without changing the image.
  • Author – Your name.  You’re the author of your image.
  • Caption – Describe the photograph clearly and concisely, and include enough information so that you could read it and know where on the planet you were when you made the photograph.
  • Copyright Status – Change this to “Copyrighted Work”.  The moment you tripped the shutter, your photograph was a copyrighted work.  Not marking this just sets you up for someone to use your photograph without your knowledge.  If you choose to license your photographs under the Creative Commons license, of course, you should set this appropriately.
  • Copyright Notice – Mine reads: Copyright © Tom Benedict
  • Date Created – The date you tripped the shutter on your camera to make the photographs that went into this image.
  • City / State / Province / Country – Fill them in.
  • Source – Give yourself some hints here.  Is it a straight shot?  Digital?  Film?  Stitched?  My digital panoramas are all marked “Digital-Stitched”.

The neat thing is that most of the photo sharing sites on the Internet will automagically read your header information and fill in their own forms for you.  You may still want to provide more information than this, but the base information will be there.

The even neater thing is that in the event someone downloads your photograph and puts it on their own site without your knowledge, your header information is indexed by most search engines.  Even better, when you challenge them and they claim the photograph as an “orphaned work”, you can demonstrate that they did not make an honest effort to find the photographer in order to ask for permission since your info is all right there with the image.

So that’s it in a nutshell.  How well does it work?  See for yourself:

Pololu Valley Wetlands 2

– Tom

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Mechanics of KAP

Posted by Tom Benedict on 28/05/2009

On the off-chance that my previous post sparked some interest in doing kite aerial photography, I’ll go into the mechanics of actually hanging a camera from a kite line, and convincing it to do what the photographer wants.  The approach used can be anything from quite simple to otherworldly complex.  A lot depends on what the photographer actually needs, but even more depends on what the photographer is convinced they want.  It’s important to keep these two ideas separate when you look at hanging a camera from a kite line.

Lightweight Rig - Ready to Fly

By far the simplest KAP rig I use is one I designed spedifically for doing mapping.  It was built for one specific trip, but it’s such a versatile rig I’ve used it numerous times since.  The requierments of the trip drove the design:  For starters, there is very little wind at the site, so lifting a heavy KAP rig was out of the question.  The bulk of the weight in this rig is the camera itself.  The rig’s weight is almost negligible.  For the purpose of mapping, all the pictures needed to be as orthogonal as possible, so there is no provision to tilt or pan the camera.  And we would need to take pictures over the course of several hours with no opportunities to change batteries during the flight, so battery life was of paramount importance.

There is no provision for the photographer to tell the camera when to take a picture.  Instead the camera is running CHDK, a toolkit that runs on top of the camera’s native firmware.  In this case CHDK was running an intervalometer script that let the camera take pictures every five seconds without any user intervention.  No mechanical linkages, no servos, no fancy electronics, just the camera itself running a pre-canned program.

Lightweight Rig Airborne

In the end the rig performed marvellously.  Complete with camera and the four AA batteries the camera requires, the rig came in just over 450g.  It flew on one set of batteries for two straight days, and took more than 2,000 photographs.  The photos from that trip are being used to map an archaeological site, and will be used in papers that should be published in the next year or so.

Current Rig - Late 2008

At the other extreme is my radio controlled KAP rig.  It’s built almost entirely out of off-the-shelf parts from Brooxes, the main supplier of commercial KAP equipment. The rig allows the photographer to pan and tilt the camera, and to operate the shutter.  Brooxes sells other components that would allow the camera to rotate from horizontal to vertical, and other accessories exist that allow the photographer additional control over the camera itself.

The rig started off as a Brooxes BBKK, but over the course of a few years I added a carbon fiber leg kit, gear reduction for the pan axis, a set of PeKaBe blocks for the suspension, and a number of other improvements.  Two changes have been made since this photograph was taken:  The first was to replace the aging 72MHz AM radio with a 2.4GHz Turborix.  The second was to remove the shutter servo and replace it with a GentLED-CHDK.  Unfortunately I haven’t photographed this rig since the changes were made.

The GentLED-CHDK is one of the cooler pieces of hardware I’ve bought for my rig.  It is a smart cable that plugs into the RC receiver on one end, and the camera’s USB port on the other.  When the photographer flips the shutter control on the RC transmitter (in my case I set it up as a switch rather than a joystick), the GentLED-CHDK sends +5V down the USB cable to the camera.  One of the features of CHDK is that you can monitor the +5V line on the USB port and take action when the camera sees it.  In my case I run a script on my camera that says as long as +5V is being applied, behave as if the shutter button is being held down.  In single-shot mode, this means each time I flip the switch the camera will take a picture.  In continuous shutter mode this means that I can hold down the switch on the transmitter and the camera will keep taking pictures as fast as it can, roughly every 1.1 second.

The two rigs are as different as they could be and still get the job done.  One was the product of a few hours of thinking and about an hour’s worth of time in the shop.  Total expenditure was maybe $50 for the Picavet suspension, most of that being the PeKaBe blocks.  The bulk of the rig came out of the scrap box.  The other was the product of a few years of tinkering with a commercial rig.  Total expenditure is probably several hundred dollars by now, but still probably less than a good carbon fiber tripod and professional ball head.

What is important to take away from this is that there is no one right way to hang a camera from a kite line.  And depending on what you actually need, an extremely simple rig like the ortho mapping rig may get the job done just as well as a more complicated, heavier rig like the BBKK.  Before becoming discouraged at the prospect of designing and building a rig from scratch, consider the commercial options.  And before becoming discouraged by the cost of the commercial kits, consider the possibility of simplifying your requirements and making one yourself.

It’s possible for anyone to do aerial photography.  If you want to do it, do it.

— Tom

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