Elphel Development Blog

Subpixel Registration and Distortion Measurement

Motivation

While working on the second generation of the Eyesis panoramic cameras, we decided to try go from capturing the series of the individual panoramic images to the 3d reconstruction. There are multiple successful implementations of such process, we just plan to achieve higher precision of capturing the 3d worlds using Elphel ability to design and build the hardware specific for such purpose. While most projects are designed to work with the standard off-the-shelf cameras, we are working on building the cameras together with the devices and methods for these cameras calibration.  In order to be able to precisely determine the 3-d locations of the features registered with the cameras we plan first go as far as possible to precisely map each pixel of each sub-camera (of the composite camera) image to the ray in space. That would require at least two distinctive steps:
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Live USB/CD/DVD

We made a new Live USB version of Elphel Toolkit.

It is available for downloading here.

Software

Elphel-Eyesis-4π preassembly stage

We have finally received the parts for Elphel-Eyesis-4π camera and started assembling them hoping that all will fit together as we planned. And for the most part they do, which seems a bit like magic to us: you design the camera on the computer in a 3D CAD program, make a long list of parts it will consist of and then a couple months later it all turns into physical object, not just a virtual 3D design. Of course some of the parts will need minor modifications – some are due to mistakes made by us, and some are manufacturing problems. But none of them were significant enough to prevent us from assembling the first 3 prototypes, that will be 100% operational spherical panorama cameras. Elphel-Eyesis-4π is the second generation Panoramic Imaging System by Elphel Inc. It is able to capture high-resolution images in full 360 degrees and create 4π (in steridians) spherical panoramas at a high frame rate. The actual recording device consists of a weatherproof camera head that contains the image sensor front-ends and lenses in spherical distribution to cover the entire 360 degree area. The rest of the electronic components as well as the SSDs for data storage are contained inside the camera pole. Elphel-Eyesis-4π covers a full sphere. 24 sensors (8 in horizontal array, 8 pointing at +30 to + 90 degree (zenith) and 8 pointing at -30 to -90 degree (nadir) ensure a uniform high resolution distribution over the entire covered area. A new Internal Measurement Unit (IMU) mounted at the top of the camera pole provides high resolution 3D position and orientation of the camera.

Fig.1. Test assembly.

Fig.2. 3D CAD rendering.

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NC353L-369-IMU/GPS

We are proud to add a new product and camera KIT to the Elphel portfolio. See the pricelist.

The NC353L-369-IMU/GPS is a new camera configuration with an Inertial Measurement Unit (IMU) and optional GPS receiver. In addition to storing the geographical coordinates with each captured image in a video stream this allows to also save 3D orientation (yaw, pitch and roll) and 3D acceleration (Six Degrees of Freedom Inertial Sensor) of the camera at the moment of capturing an image at very high precision (2400 samples/second). A detailed description can be found in the previous post.

Eyesis outdoor panorama sets and the Viewer/Editor

WebGL Panorama Editor (view mode)

This April we attached Eyesis camera to a backpack and took it to the Southern Utah. Unfortunately I did not finish the IMU hardware then so we could rely only on a GPS for tagging the imagery. GPS alone can work when the camera is on the car, but with a camera moving at pedestrian speed (images were taken 1-1.5 meters apart) it was insufficient even in the open areas with a clear view of the sky. Additionally, camera orientation was changing much more than when it is attached to a car that moves (normally) in the direction the wheels can roll. Before moving forward with the IMU data processing we decided to try to orient/place some of the imagery we took manually – just by looking through the panoramas, adjusting the camera heading/tilt/roll to make them look level and oriented so the next camera location matches the map. Just tweaking the KML file with the text editor seemed impractical to adjust hundreds of panoramic images so we decided to add more functionality to our simple WebGL panorama viewer, make it suitable for both walking through the panorama sets and for the editing orientations and locations of the camera spots. (more…)

IMU and GPS Integration with Elphel Cameras

CAD rendering of the Analog Devices ADIS-16375 Inertial Sensor, 103695 interface board and 103696 serial GPS adapter board attached to the top cover of NC353L camera

For almost 3 years we had a possibility to geo-tag the images and video using external GPS and optional accelerometer/compass module that can be mounted inside the camera. Information from the both sensors is included in the Exif headers of the images and video frames. The raw magnetometer and accelerometer data stored at the image frame rate has limited value,  it needs to be sampled and processed at high rate to be useful for the orientation tracking , and for tracking position it has to be combined with the GPS measurements.

We had developed the software to receive positional data from either  Garmin GPS18x (that can be attached directly to the USB port of the camera) or a standard NMEA 0183 compatible device using USB-to-serial adapter. In the last case it may need a separate power supply or a special (or modified) USB adapter that can provide power to the GPS unit from the USB bus. (more…)

Panoramas From the Backpack

Eyesis Backpack with Netbook for initial set-up

Tacking high-resolution panoramic images in the remote places, that can only be accessed by feet is an option now available with the Elphel-Eyesis 360 degree panorama camera. The camera’s size (1.3 x 0.3 meters) and relatively light weight (10kgs) allow to mount it on a backpack frame and carry by a person.

There were multiple requests for the backpack option by our customers since the development of Elphel-Eyesis camera, but other projects were of higher priority, until this spring, when we finally decided it was time to take Eyesis hiking.  After all, we have worked hard on this project for many months, so we ought to have some fun with it too, and take panorama images of the places we knew and enjoyed for it’s scenery.

On April 19th, 2011, we took the Elphel mobile office to camp for 5 days in Southern Utah near the Goblin Valley State Park to try out Eyesis in beautiful places not yet available in continuous panoramic imagery, mainly because of their inaccessibility for car, ATV, or even a tricycle.
Hiking with Eyesis in the backpack (30 lbs/14 kg total weight with the battery pack) allows us to capture a continuous stream of geotagged (GPS) 360° panoramic images. With the current battery pack (just a regular UPS with lead battery) we can take up to one hour and forty minutes of footage at a rate of 5 frames per second.
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Google API V3: Custom StreetView

Click here for the active view (resizeable)

Description

Works in Firefox 4.0 and Chrome. Does NOT work in Firefox 3.6.X.

The above sample shows how custom panoramas (in our case: a panorama we shot with our Elphel Eyesis) can be integrated in a custom StreetView.

Elphel Eyesis images is the top-left window. The top-right window is the current (lower resolution) official Google Street View in Salt Lake City supposedly made by the 2nd or 3rd generation of GSV cameras.

The Open Street Map is for switching between the available panorama points and the Google Map with a pegman is filling the otherwise unused space at the same time generously showing the view direction.

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Hardening the Asterisk-based phone system

Last week our phone system was broken into and we’ve got a phone bill for some five hundred dollars for the calls to Gambia. That expense was not terrible, but still that amount is usually enough for many months of the phone service for our small company – the international phone rates in the VoIP era are (for the destinations we use) are really low. The scary thing was that the attack lasted for very short time – just minutes, not hours, so our damage could be significantly higher. (more…)

Open Street Maps and Google Maps APIs

   

Both, Google Maps API and Open Layers API, are quite simple, though it can take some time to find a perfect example. The maps are added to the WebGL panorama view test page (read “Experimenting with WebGL panoramas”)
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