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The Kinect is a new sensor and is actively being used and researched, and new uses and information appears frequently. I cited what I could in my paper, but some of that information is already out-dated. In the comments below I attempt to catalog new projects, studies, publications, and information as it becomes available.
Tags: Code, Computers, HowTo, Kinect, ResearchA manuscript by Mankoff and Russo entitled “The Kinect: A low-cost, high-resolution, short-range, 3D camera” has been accepted with minor revisions by the journal Earth Surface Processes and Landforms (ESPL).
It can be cited as doi: 10.1002/esp.3332
I’m about to embark on my third trip underneath a glacier within the past 13 months. I’m taking the time to write up the first two trips now, so that next month when I go on the third trip there is some context and some record in case I don’t return (I will be rappelling down a dry moulin and spending time underneath a glacier that will likely have polar bears on top). I also want to share the experience here because it was interesting and special and I hope to educate others about some unique field sites and engineering feats.
The first trip occurred in September, 2011. My collaborator Jason Gulley and I drove a short distance from Longyearbyen, Svalbard, and then hiked to the nearby Rieperbreen glacier. We crawled up the snout of the glacier, and tested the Microsoft Kinect as a low-cost 3D camera to measure the roughness of the rocky floor and the scalloped ice roof. Although just a proof-of-concept, that work was written up by Wired, and led to an invitation for my second sub-glacial trip.
Unloading personnel and equipment from a hovering helicopter.
In April 2012 the Svartisen Subglacial Observatory hosted a Subglacial Workshop. Compared to hiking and then crawling through 0 C degree water into the glacier, this trip was relatively speaking a luxury. It began with a helicopter ride, but the helicopter, unable to land on the snowy mountainside, hovered with its nose touching the mountain while we climbed out of it (Note: climbing into a hovering helicopter is a bit more difficult than climbing out of one). After the helicopter departed, I noticed a door in the side of the mountain.
Entrance to the Svartisen Subglacial Observatory
Svartisen Subglacial Observatory mine shaft
The Svartisen Subglacial Observatory entrance is a door into a mountainside. Once inside, a km-long tunnel contains a living area able to house 8 scientists, a research laboratory, and several places with direct access to the bed of the glacier. The end of the tunnel that is not on the side of the mountain literally ends at the edge of the rock part of the mountain, but underneath 200 m of ice. There is no sunlight in this mine shaft, and one instantly feels disconnected from the outside world after entering and closing the outside door.
The living units are similar to those we live in when in Antarctica (when not in a tent): Shipping containers retro-fitted for humans to live in. There is a kitchen, rooms with bunk beds, and a bathroom and shower. There is electricity, but no internet. The water is fresh and cold. A 15 minute walk farther up the tunnel to the office and there are experiment benches and work space, and surprisingly, a WiFi signal with slow internet access to the world beyond. Another 5 minute walk to the end of the tunnel, and there are holes in the bedrock leading to the bed of the glacier, and a door big enough to walk through. Several times a year, scientists open the door and with a hot-water hose melt a cave, several cubic meters in size, into the bed of the glacier. This cave creeps closed quickly due to the weight of the ice above and around it. The room shrinks to about 1/2 its size every 24 hours, and the cave is completely closed within a week.
The temporarily-created subglacial cave melted in the Svartisen Subglacial Observatory. Brown bedrock with embedded pressure sensors is seen in the foreground, and the slowly creeping gray/blue ice in the background.
My third sub-glacial trip will happen in October 2012 underneath the Hornsbreen Glacier in southern Svalbard. We will rappel down an empty moulin to access the subglacial cave system.
Algorithms for the Kinect have been much improved since my first trip (for example, see Kintinuous and ReconstructMe), and we hope to make full 3D maps of the cave system. This third trip has been funded by the Svalbard Science Forum Arctic Field Grant, and I will describe it in more detail after it happens.
I know of only a few people that attempt to personally explore the subglacial environment, and am excited to partake in some of those expeditions.
Tags: Kinect, Research
I am releasing source code for a program that supports off-line calibration and registration of raw Kinect data collected by the libfreenect record program. The interesting parts of this code were all developed by the OpenKinect community, I simply patched parts of their code together in a way that was useful for my Kinect work. I have argued in the past for collecting the raw data so that different (and better) calibrations can be applied in the future, and this code maintains this philosophy.
This code uses the internal calibration parameters that are shipped with each Kinect, as opposed to extrinsically determining the calibration (the method used by most checker-board image calibration methods). Offline means that the calibration parameters can be captured once when the Kinect is plugged in, and then used in the processing phase without the Kinect on data that has already been acquired. Calibration is defined as the act of mapping from the raw sensor digital numbers (DN) in (pixel, pixel, DN) coordinates to world (x,y,z) coordinates. Registration is defined as mapping the RGB pixels onto the depth data.
Importantly, this registration maps RGB to depth, whereas all other registration algorithms I know of map depth to RGB. Since the data of interest with the Kinect is the depth data, it does not make sense to perform any unnecessary error-increasing mathematical operations on the depth data.
The code can be downloaded from https://github.com/mankoff/libfreenect/tree/offline_register and built with the following commands, assuming all dependencies are already installed. The easiest way to verify your are able to build this code is to install libfreenect through an existing package manager system, then over-write that with this custom build.
git clone https://github.com/mankoff/libfreenect/
cd libfreenect
git checkout offline_register
mkdir build
cd build
cmake ..
make
make install
Optionally, skip the make install line and access the new program in build/bin/. The new program is called “kinect_register” and when run without any arguments it prints usage instructions:
$ kinect_register
Kinect Offline Registration
Usage:
kinect_register [-h] -s <regfile> | -a <regfile> <PGM> [<PPM>]
-h: Display this help message
-s: Save the registration parameters from a connected Kinect to <regfile>
-a: Apply the registration from <regfile> to <PGM> (from 'record')
Optionally align a PPM file with the PGM file
Data Formats (units: mm):
file.x: 640x480 double of x values
file.y: 640x480 double of y values
file.z: 640x480 integer of z values
file.xyz: ASCII file of x y z r g b. RGB only if PPM argument provided
file.reg.ppm: PPM shifted so pixels align with file.{x,y,z} data
The role of Pine Island Glacier ice shelf basal channels in deep-water upwelling, polynyas and ocean circulation in Pine Island Bay, Antarctica
Several hundred visible and thermal infrared satellite images of Antarctica’s southeast Amundsen Sea from 1986 to 2011, combined with aerial observations in 2009, show a strong inverse relation between prominent curvilinear surface depressions and the underlying basal morphology of the outer Pine Island Glacier ice shelf. Shipboard measurements near the calving front reveal positive temperature, salinity and current anomalies indicative of melt-laden, deep-water outflows near and above the larger channel termini. These buoyant plumes rise to the surface and are expressed as small polynyas in the sea ice and thermal signatures in the open water. The warm upwellings also trace the cyclonic surface circulation in Pine Island Bay. The satellite coverage suggests changing modes of ocean/ ice interactions, dominated by leads along the ice shelf through 1999, fast ice and polynyas from 2000 to 2007, and larger areas of open water since 2008.
@article{Mankoff:2012The-role,
Title = {{The role of Pine Island Glacier ice shelf basal
channels in deep water upwelling, polynyas, and
ocean circulation in Pine Island Bay, Antarctica}},
Author = {Kenneth D. Mankoff and Stanley S. Jacobs and
Slawek M. Tulaczyk and Sharon E. Stammerjohn},
Journal = {Annals of Glaciology},
Number = {60},
Volume = {53},
Year = {2012},
DOI = {10.3189/2012AoG60A062}}
Tags: Antarctica, map, NASA, NBP09-01, PhD, Pine Island Glacier, publication, Research 
Pine Island Glacier and Pine Island Bay
Pine Island Bay in the southeast Amundsen Sea, Antarctica, on 16 Nov 2008. Upwelling, melt-laden outflow plumes emerge from beneath the adjacent Pine Island Glacier ice shelf (top center) and mix in the bay waters. Warm red colors show sea surface temperatures more than a degree warmer than the near-freezing dark blue color. Cyclonic circulation in the bay is framed by the ice shelf, land ice and sea ice, in gray-scale with the darker shades colder. Landsat Enhanced Thematic Mapper Plus image, thermal infrared (channel 6H), subset of scene #LE72331132008321EDC00.
@article{Mankoff:2012The-role,
Title = {{The role of Pine Island Glacier ice shelf basal
channels in deep water upwelling, polynyas, and
ocean circulation in Pine Island Bay, Antarctica}},
Author = {Kenneth D. Mankoff and Stanley S. Jacobs and
Slawek M. Tulaczyk and Sharon E. Stammerjohn},
Journal = {Annals of Glaciology},
Number = {60},
Volume = {53},
Year = {2012},
DOI = {10.3189/2012AoG60A062}}
Tags: Antarctica, ice, map, PhD, Pine Island Glacier, Places, publication, Research, Visualization Last week I presented a poster at the 2011 AGU Fall Meeting. It has generated some press thanks to an article in Wired. If you are interested in the poster it is available by clicking on the image below.
AGU Poster: `Kinects as sensors in earth science: glaciological, geomorphological, and hydrological applications`
@conference{Mankoff:2011Kinects,
Author = {Kenneth D. Mankoff and Tess Alethea Russo and
Benjamin Kenneth Norris and Saffia Hossainzadeh and
Lucas H. Beem and Jacob I. Walter and
Slawek M. Tulaczyk},
Title = {{Kinects as sensors in earth science: glaciological,
geomorphological, and hydrological applications}},
Address = {San Francisco, CA},
Booktitle = {American Geophysical Union, Fall Meeting},
Month = {December 5 - 9,},
Note = {Abstract \#C41D-0442.},
Year = {2011}}
Tags: Kinect, Media, PhD, publication, Research Following up on my previous post about using the Kinect for earth science applications, I’m documenting the Kinect Go Kit I built for fieldwork.
Kinect Go Kit: Top level
Kinect Go Kit Pelican Case
I travel with two Kinects, two power supplies, and two computers in case one gets damaged or destroyed in the field, although only one computer is in the kit.
The Netbook is a cheap $240 computer running Ubuntu and the libfreenect software stack at a minimum. I have also found it useful to have more advanced data collection software (ROS, RGBDemo, RGBDSLAM), and some analysis software (CloudCompare, points2grid, Viewpoints, etc.). This netbook works fine for raw data dumps from the libfreenect ‘record’ program. It can run the more computationally expensive scene stitching algorithms such as RGBDSLAM, but it takes about 10 seconds per stitch, while a more powerful laptop (but still a few years old) can do it at 0.5 to 1 Hz. Since ‘record’ collects about 1.5 GB of data per minute, it is good to have a lot of free space on the hard drive.
The plugs and cables are shown laid out below, and in addition, some velcro straps are stored in that compartment, used to attach the Kinect to the tripod arm.
The Pelican 1510 case supports two levels, and the lower level looks like this:
Kinect Go Kit: Bottom level
Battery #1 is a 12 V 5 Ah sealed led acid battery. It provides >5 hours of Kinect runtime, about equal to the runtime of the netbook.
Battery #2 is 8 AA batteries (12 V), and underneath is an 8 AA battery holder and a battery charger. If I need to turn the Kinect on for a short amount of time and want to travel lightly, these will do.
Kinect cable layouts
As shown above the cord to the Kinect can be cut and alligator clips or some other electrical termination can be attached. I often have wall power and have attached clips to the detached plug so I can use it as originally intended. However, when in the field, the clips can connect directly to the 12 V battery or the AA battery pack.
Kinect mounted on tripod
The Kinect Go Kit above is close to the minimum necessary for fieldwork. Things that I would like in it, but are not yet, include:
Additional tools I have found handy to have with me in the field include, but are not limited to, the following:
Tags: Computers, HowTo, Kinect, PhD, Research
We have successfully used a Kinect outdoors to study ablation on a glacier, map a subglacial cave in 3D, and tested it in a variety of hydrological situations (imaging roughness on the base of a stream, calibrating the Kinect data through water, and imaging surface waves). Results will be presented at the 2011 AGU conference.
There are a variety software interfaces to the Kinect. One high-level tool that is easy to use (binaries provided, no need to compile source, supports ‘scene painting’) is RGB-Demo. It is a good tool to start with if you want to work with the Kinect.
However, most Kinect software and calibrations so far have been developed by the robotics and computer vision communities. I am grateful for the work they have done, but those communities have different data needs than earth scientists. For example, quadrotor obstacle avoidance (link (PDF), link) has distance measurement errors that appear to be on order cm, but it still works fine as the helicopter avoids obstacles by an amount larger than the error.
Earth scientists should aim for a better model of the world than the one currently provided by the Kinect and its primary users. I suggest recording and storing the raw digital numbers (DN) from the Kinect rather than higher-level auto-calibrated real-world coordinates. It will require more post-processing, but storing the DNs will allow the data to be re-processed as better calibrations are developed. In addition, the low level recorder operates at 30 Hz and the higher level point-cloud products currently do not record data at that rate.
The best supported low-level interface is the LibFreenect Fakenect record program. It dumps the uncalibrated RGB and depth images to a folder at 30 Hz until you kill the process. Uncalibrated means both that the depth data is in sensor units, and that the depth and RGB images are not aligned. You can easily convert the depth data to real world x,y,z coordinates using existing published algorithms (link, link, link, and many others exist on the web), but importantly the raw data is stored and can be used with better calibrations in the future.
After processing the raw ‘record’ data, you can work with the point cloud data or DEMs using a variety of standard software for pointclouds, LiDAR, etc. I have had great success with CloudCompare and Poinst2Grid, in addition to custom code in MATLAB, IDL, and Python. A good list of software is available at the NSF OpenTopography site.
To work with the depth data to we initially use the following algorithms found on the various sites dedicated to Kinect hacking. The data provided by these algorithms is sufficient for certain uses, and for testing algorithms and visualizations, while better calibrations are performed.
DN to distance (source):
k1 = 1.1863d
k2 = 2842.5d
k3 = 0.1236d
Z = k3 * tan( double( DN ) / k2 + k1 )
XYZ to world (source):
Xres = 640
Yres = 480
FovH = 1.0144686707507438 (rad)
FovV = 0.78980943449644714 (rad)
XtoZ = tan( FovH / 2 ) * 2
YtoZ = tan( FovV / 2 ) * 2
X = ( X_pixel / Xres – 0.5 ) * Z * XtoZ
Y = ( 0.5 – Y_pixel / Yres ) * Z * YtoZ
Question or comments? Post below…
Tags: Code, Computers, HowTo, Kinect, ResearchIt has been almost one year since the Kinect was released, and there have been some amazing projects that use it. Microsoft appears to be embracing the hackers and highlights some of the non-video-game related uses in a new video:
Tags: Computers, Kinect, Research, Video
Also of Interest…