Nikon Hotshoe IMU with Xadow Modules

Hotshoe GPS-IMU in enclosure

We take lots of oblique images from a helicopter for our high-resolution 3D modelling service - Aero3Dpro. While photogrammetry and aerotriangulation lets us establish the position and orientation of these photographs afterwards from a relatively poor initial GPS and no IMU, just after capture there is no indication how well an area is covered from different angles. This can be a pretty difficult proposition anyway, especially in the presence of narrow allies and tall buildings. However with a good initial GPS-IMU one could build a low resolution model of the city literally on the fly.

All the components that get packed into the GPS-IMU

So I set about building a system that fills this niche, a camera hotshoe mounted system with a reasonably accurate GPS and IMU. There are already a lot of existing Xadow modules which satisfy the requirements of the system. I just had to cook up a few more as described in a previous post to cater for the unique requirements for interfacing with the camera and logging the data.

1. Xadow Barometer
2. Xadow 9-DoF IMU (can be combined with 1 above in the new 10-DoF IMU)
3. Xadow GPS  (the NMEA from the stock one does not agree with the Nikon so looking at a UBlox based version)
4. Xadow OLED
5. Xadow-M0 with MBed support
6. SPI to Dual-UART with SC16IS752, this is necessary because the only available UART on the Xadow-M0 is consumed by the GPS. We need 2 more UART's to send data to BLE module and camera at 4800 Baud.
7. Xadow BLE Module  
8. Xadow SD for logging locally in case BLE connection is patchy or a non-Nikon camera is being used which does not allow geotagging over UART.

A lot can be done when all these modules come together to party, the mBed code is available here. The android app for receiving the GPS-IMU data over BLE and predicting the camera foot print is still in the works. If anyone wants to take the app development up as an excercise I can provide the source. In conclusion I must thank Kris Winer for excellent IMU test beds and sample codes which helped me get started down this path.

GPS-IMU on hotshoe mount

After all the electronics came the enclosure and hotshoe attachment system. I designed something rough in blender using a trace of the stacked PCB's and got it locally 3D printed by 3D Hubs and Andrew Karas. This mounts nicely on the hotshoe, but the openings for reset, USB and cable to camera are not neat, a more aligned box is in the works.

Medieval Fair 2013 - Making rings for chainmail

I have dressed up as Robin Hood and gone to the Medieval fair in Gumeracha sporting a bow. This year I decided to sport my camera with the classic 20mm pancake instead. The first thing I walked into was a sword holding competition. The challenge was to hold a 15 kilo sword with the arm extended horizontally for as long as possible. Plenty of fitness instructors and heavy lifters had a go at it, the record while I watched was around 3 minutes. I think I am going to practice with a cricket bat for next year.

Being a builder builds muscles

There were also jugglers and irish dancers, and to my dismay people with huge amounts of camera gear shadowing them. I felt really unprofessional with my dinky m43, then again this is the age of mobile photography and the battle between processing vs gear is on. It is now even being used as a marketing point by those Sony NEX ads. Granted a micro-four thirds sensor is smaller than the APS-C, still the weight advantages and flexibility bonuses do apply.

Juggler practicing

There were a few knights in chainmain and I walked into a conversation involving effort and time that goes into making the armor. Eventually the talk drifted to cheap Indian labour working for $1 a day so that people can have fun the fair, at that point people glanced at me and stopped talking. I should start tinkering with fencing wire to keep the stereotype going. Some things cannot be mechanised yet, clothing be it out of fibres or metals is one of them. The economics of hobbies is also interesting.

Riveted chainmail

The melee of kids with pugil sticks reminded me of a Schlock Mercenary episode. It will be good to get some excercise done while in costume.

Pugilists not boxing

There were also Middle eastern belly dancers and scribes doing calligraphy while complaining that the Belly dancers are not Medieval. Though the ululation accompanying the dancing is fairly universal.

Belly dancer and musician

Finally I managed to put the 850mm IR filter to good use and capture a panorama including the little lake at the Viking encampment. Without special IR modifications to the camera I had to use a pretty high ISO (1600) and a 2 second exposure. The processing through RawTherapee worked fine using some IR profiles I found floating around in Github, Hugin did a fair job of stitching as well.

850mm IR filter with unmodified camera panorama

Adelaide Mini Maker Faire, Zoo and Indian Mela

I have been involved with the Adelaide Hackerspace on and off. Lately my attendance has dropped a lot due to work commitments and a casual addiction to photography. A few photography related hacks are stewing in my brain, so I might go back there. Anyway a few weeks back I went to the Adelaide Mini Makerfaire and it was great opportunity to see all the different things going on in Adelaide, from Dalek making, Metal working to 3D printing and Electric cars. I had a great time catching up with people and learning about new groups. The airstream guys had some hacked wireless AP's on display, including the Minitar on which I cut my teeth in cross-compiling and writing kernel modules to interact with the wifi-stack. There are a lot more photos.

I had planned a busy day, so I headed off to the zoo to attend the local photography group session and check out some pandas. It was my first time at the Adelaide zoo, so it took a while to get oriented. We covered a fair bit of ground in the hour and a half before closing. Managed a few shots of hippos, birds, otters and mountain goats. Lots of other animals which hardly stood still enough to compensate for my nascent photography skills.

We were trudging and hobbling back to the car when we noticed the bright lights and steady stream of people heading to Elder park. The local indian community was throwing their annual mela. So we headed there for a meal and to feed our cameras with some colour. The movement and low light made photography pretty difficult from the back of the crowd. It was a great day overall.