We generally prefer the manual "yo-yo" reels because of their durability. Those little winders you're using definitely break at high loads. I have one of these as well, its a little tricky and the string can jam up the brake if I'm not careful. its nice for flying alone, but when two or more people are with me I go to the yo-yo reels-- they're easier to learn on and simple enough not to cause much trouble. On my own the yo yo isn't bad either, but if I have to rapidly pull in a lot of string I'll have to drop the reel and make a mess.

Great report. The mini bottle and 3D printed Picavet will go in the Public Lab record books. And what a fantastic place to fly. Is that public land?

It's too bad about the little camera. I'm glad to hear you were able to retrieve the kite.

I bought one of those line winders too. It came with a $5 discount on another purchase, so I bought a second one. I used it once and have not touched either one since. They could work for ballooning, but are a liability for kiting. You can't beat a halo reel for convenience and effect.

Fifty pound Dacron is a little lightweight. Was it really 50 lb? 150 pound is the minimum line weight for a lot of KAP people.

ActionCams and Pi Cams and other little cameras have advantages, but most of them don't cost less than a $40 ebay or refurbished Powershot which will take photos which are actually useful. Your result at Potts Point confirms that you made a good decision to fly a low end camera, but when the wind is behaving and you have the correct kite, a decent camera might be worth the risk. I decided early on that kite photography was too much trouble unless I could get good quality photos.

Thanks for the story.
Chris

Hmm, i'm not sure what's going on with that mapknitter export. Looking into it... thanks!

I can't tell if there's something it's choking on in your images (maybe 'cause they were screenshots from VLC?) or it's having trouble downloading them from Amazon s3 after up you upload them. It errors with:

identify: magick/splay-tree.c:880: GetValueFromSplayTree: Assertionsplay_tree != (SplayTreeInfo ) ((void )0)' failed. Aborted`

but that's not very helpful, and could just be what happens when you call identify on a nonexistent image? But when i run identify on a truly non-existent file, i get identify: unable to open imagesadjlfkads': @ error/blob.c/OpenBlob/2489.` so maybe there's really something it can't deal with in the images...

Indeed there's something about the images themselves. I hate to ask, but could you try to convert them to jpg and re-upload them? I'm very sorry but since there are only 3 i hope it won't be too big a setback?

RE: Mapknitter- I converted the images to JPGs and uploaded them again. The export status dialog then reads (Status: Warping 1 of 6, 2 of 6 etc.) until it gets to 5 of 6 where it just hangs. This is definitely an improvement over last time however wherein it showed no status at all. I did use DigiKam to convert the images to JPGs and I can't remember if I used it the first time. I certainly hope the error doesn't trace back to DigiKam because it seems so well suited to the needs of batch editing.

RE: Kite Reels and Line- It was definitely 50 Ibs line but now that I know better I made sure to order a Yo Yo Reel with 150 Ibs Dacron this time. In hindsight it validates my decision to use the lighter cheaper camera all that more! As I mentioned earlier, I ordered a Mobius Action Cam that should be arriving tomorrow so I'll have the weekend to go over various options for the Picavet/Rig before the new line arrives. It certainly helps to have a 3D Printer, but with only 4x4x4 to work with I'll have to get creative.

RE:-High Winds- Has anyone posted a note about making a DIY wind speed meter? It would've been handy to get a rough idea of how close I was to the kites limits. I tried various Android apps that claim to calculate wind speed by measuring distortion in the phone microphone, but all were completely useless when I tried them in the field...
There seem to be a few "DIY Anemometer" tutorials on KAP forums and Instructables but they all seem to be for full anemometers, meaning it also measures wind direction. In my case direction wasn't all that important... I have an old PC fan with an analog output I was considering hacking into one of those attachments for the smartphone that go in through the headphone jack, but I wanted to see if anyones tried it already.

Hi,

Great project.

I do multi rotors, rc planes, blimp and kite pics.

Your pictures will be 100 times better with a Mobius, plus a waterproof case. 100 dollars, intervalometer inside, quite shockproof.

You will need Gimp and bimp to automatically make the pics square, and you can use agisoft photoscan for composing the whole picture.

Best of all, you can even make 3D images of your same project, from the exact same software and hardware, like I do here : https://www.youtube.com/watch?v=iOmtm0G-AJQ

Cheers

Thank you for the interesting recommendations. I actually just got my Mobius today and will be printing out various components for the rig. Can you recommend a good waterproof case? I certainly learned my lesson last time... I was not aware of the Bimp plugin though I use Gimp frequently. I was very impressed with DigiKam and was going to propose a side project aimed at configuring a preset template for aerial mappers or possibly a plugin for MapMill. But something along those lines would make much more sense for Gimp considering it has such a large user base. Can I ask if you've tried DigiKam before? If so how does it compare to Gimp+Bimp? Have you tried Mapknitter yet? If not I'm sure the devs would be interested in your input since you've worked with professional-level platforms. Some might dismiss the need for 3D but grassroots mapping is one application where 3D could be a game changer! It looks like Agisoft Photoscan uses some form of Computer Vision to add their 3rd dimension. I wonder if it would be possible to do something similar with OpenCV? Though it looks like the Agisoft Suite is proprietary? If so their technique might be patented...

Links to waterproof case (the only case I am aware of ) Video : https://www.youtube.com/watch?v=sy8ONQOhha8 Purchase : https://joovuu.com/gb/home/103-mobius-waterproof-case.html

Instead of using photoscan you can have a look at visualsfm / cmvs, it is just too complicated for my primitive knowledge of photogrammetry.

I had not heard about any of the software you mentioned, I will have a look :-)

One picture I took recently from the Mobius so you can have a flavour of what it can provide, at a rythm of 1 image every 2 seconds.

That is the "black island" from Tintin album cover. My multicopter is hand made with super cheap material, it is therefore vibrating a lot. From a kite / picavet, no doubt you will have crisp pictures despite low resolution.

Sorry two more things for you : - make sure you use pulleys and proper pulleys string on your picavet. Brooxes.com is the place. My picavet / pulleys from Brooxes are 10 year old and still going strong. - try free software microsoft ice if your pictures are flat enough ( not taken at an angle)

That is an excellent Mobius photo. The Mobius is so lightweight that there is no reason not to include one on every flight. The lens is very wide, so stitching maps from multiple low altitude photos produces poor results. The zoomed mode of the Mobius just uses the center part of the sensor so the resolution suffers. I don't know whether structure from motion algorithms can deal with very wide angle photos.

There is a very involved workflow for sfm using free programs. Brenden Duffy made a couple of tutorials that are linked here to my only attempt to do it. Very involved, but effective.

The PeKaBe blocks that Brooxes sells are excellent for Picavets, and help a lot with very lightweight rigs. But for normal rigs with the camera mass a few inches below the Picavet cross, and with soft line lacing the Picavet, smooth eyes work fine to keep the rig level. It's hard to justify $60 for four blocks, although they are beautifully engineered.

"The lens is very wide, so stitching maps from multiple low altitude photos produces poor results"

Sorry for not being clear enough. Gimp + Bimp allow you to automatically (batch) take the barrel effect out of every Mobius picture, making Mobius pictures "stitchable".

For instance, this was done from a few hundred Mobius pictures with barrel effect out thanks to Gimp + Bimp : https://www.youtube.com/watch?v=vK-3joqFIWA

Now I can't wait to get back in the air because I really want to compare the Bimp+Gimp combo to DigiKam. I have a slight suspicion that DigiKam postprocessing is causing some kind of file corruption in Mapknitter however, so I hope the same doesn't prove true with Bimp/Gimp.

That's good to know that structure from motion works with wide angle photos. It sounds like you have to correct the distortion first. It doesn't seem like making a flat map would work very well with wide angle photos even after the photos were corrected, because the ground is viewed from many different angles in each photo.

Also a brief search into OpenCV and 3D Aerial Photography yielded some promising results- This post on Stack Exchange almost seems like it came from someone at PublicLab- http://stackoverflow.com/questions/22180512/algorithm-for-ortho-rectification-mosaic-ing-aerial-images. Mathew, CFastie, and Warren- Has anybody examined the use of OpenCV for 3D Ortho-Rectification? Or is this a new discovery? If so I'll post a new research note about it.

I haven't seen anyone doing orthorectification with Open CV. MicMac is the only toolchain I know of it include 3D construction and orthorectification https://publiclab.org/notes/mathew/02-25-2014/3d-data-from-image-sets-autostitching

On anemometers-- learn the Beaufort scale and watch the tops of trees-- since wind speed on the ground is less important than high up, Beaufort is more useful than an anemometer. its not as precise, but its more accurate and useful. I had a pocket anemometer for a while but it wasn't worth it. I don't use one anymore. https://en.wikipedia.org/wiki/Beaufort_scale

Hmm, trying again now: https://mapknitter.org/map/view/pottskaptest2/

It worked this time! Not sure what your last error was but it seems converting to JPG was OK.

cfastie- Now that I'm back in the air, I definitely see what you're talking about with the lens distortion... My latest attempt- http://archive.publiclab.org/leaflet/?tms=https://mapknitter.org/tms/low-tide-potts-point/&lat=43.7319613151&lon=-70.0234926588

I forgot about the Gimp/Bimp method suggested by Philgib though so I will try it.

Philgib- I tried using the GIMP+BIMP combination that you suggested and it seems relatively straightforward. The only problem is I have no way of knowing how to set the lens distortion correction values. When working with a single photograph it gives you a live preview, but the batch processing menu has nothing of the sort and the parameters are different so I can't just copy them over from a single image. Can you maybe go into a little more detail about how you used Gimp for batch processing Lens distortions?

Sure. I won't say I have the best way to do it but that works for me for many different lenses.

Take a picture of that screen : http://1.bp.blogspot.com/_0zx-4pM8HnA/TSltkqjXscI/AAAAAAAAAI0/45MJoCS5-f8/s1600/OpenCV_Chessboard.png

Go to Gimp, open that picture, use filter=>distortion=>lens distortion, and play with settings until you have the picture square

For batch treatment, go to Bimp, click on the Add button, open the "open other bimp procedure", then choose plug-in-lens-distortion and use the same parameters as for gimp, then select directory or files, then Apply

My gimp is in French so options may not have the exact same wording but you should get the idea. Let me know if that works for you too.

You may also watch this : https://www.youtube.com/watch?v=hiiYW5cMGII

Cheers

Phil

I guess I read your question too fast or it is too late here (past midnight) or I am too old... Anyway...

I am using the first 2 variables in the Gimp lens distortion section, and amount of 2nd order and 4th order on Bimp plug-ins-lens-distortion.

Yes, I conducted my own test by correcting values using both menus on two copies of a single photo and the photos came out identical.
This is how the values seem to be translated-

Using GIMP-Lens Distortion-

and using BIMP Batch Editing dialog-

Its rendering now, so hopefully it makes a noticeable difference when I try to upload onto a new map. If not, I was looking into the HUGIN Panorama editor which has lens correction and batch processing but makes Gimp look like iPhoto in terms of complexity... So I'm hoping it doesn't come down to that...

How did i miss this note?

excellent discussion, y'all

I wrote this up after a chat with mathew http://publiclab.org/notes/eustatic/11-11-2014/a-method-for-distorting-mobius-action-cam-imagery-in-gimp-foss