Data Collection (How to Digitize the World)

What do you do when you've found all the pre-recorded data that exists, but need more detail?  There are many places for which such data (aerial, satellite, road, vegetation, structures etc.) are either too expensive, inaccurate, or unavailable.

In the perfect world, there would be a device that you simply carry around, and it would sense and measure everything and build a database automatically.

GPS

• GPS (Global Positioning System) devices are now quite cheap and accurate
• The GPS Resource Library has useful links
• a typical consumer unit: Garmin eTrex GPS
  • a handheld unit about as big as a cell phone, around $150
  • you can set and name waypoints, record tracks and play them back in reverse
  • battery life of ~30 hours on two AA's
  • with good sky visibility, horizontal accuracy is 5-7 meters
  • has a serial interface; you can either buy their custom cable ($38) or cobble one together yourself
• more expensive models also have a built-in compass and barometric altimeter (GPS altitude readings are pretty inaccurate)
• there is a standard file format for GPS data like waypoints: GPX the GPS eXchange Format, though it is still early in its adoption stage
• Garmin publishes their Communication Protocol Interface Specifications to enable custom software to communicate with their devices
• DGPS - Differential GPS
  • see all about Differential GPS
  • decreases error (to less than 1m) by using another antenna and a transmitter at a known ground location
  • the system is therefore more much expensive (typically >$5000)
• WAAS - the Wide Area Augmentation System
  • improves accuracy to 1–2 meters horizontal and 2– meters vertically, similarly to DGPS
  • unlike DPGS, works with exiting GPS receivers, provided their software is upgraded
  • only covers the USA, won't be entirely functional until 2006
• the latest DeLorme Earthmate GPS Receiver is WAAS-enabled, and the Professional model claims that post-processing software allows for sub-meter accuracy
• a big problem with GPS is that it needs line of sight to at least 3 satellites to get an accurate fix, which means its of limited usefulness in places such as dense cities or dense forests
• Trimble News Release: 03.02.27 announcement that they will develop technology to "Allow Acquisition of Location Information in Difficult Environments—Urban Canyons, Parking Garages and Even Indoors"

Portable Data Collection Devices

• Surveylab - ike
  • incorporates a GPS, an electronic compass, a laser distance meter, an inclinometer, a digital camera, and a Pocket PC 2003 handheld in a single unit
  • the GPS has normal accuracy (~5m) but also allows some additional accuracy via:
    • DGPS Post Processing (using Waypoint's GrafNav Lite)
    • RTCM 'Real Time' DGPS
    • SBAS (i.e. WAAS and EGNOS)
  • laser has a range of 100m, though 30m is more typical
  • costs $8500
• Personal Pilot from GeoPerception [site gone?]
  • a (proposed) hardware/software solution that allows users to interact with GIS data in the field using a lightweight, wearable, hands-free system
  • included a Positioning Engine which combines a GPS receiver, a differential signal receiver (for <2 meter), a heading decoder (<2 degrees) and a computer with custom data and software
  • their DGPS used the free 300 KHz differential signal
  • hardware base was a Xybernaut wearable PC
  • the software enables you to query features by looking at them, to log data to your GIS by walking about, to have a continuous 'bird's eye' perspective of where you are in relation to your data, etc.
  • contact: Dave Caswell, estimated cost $10k
• The ART+COM UJP
  • differential GPS (<1 meter)
  • high precision electronic compass
  • stamps every single piece of information that is recorded by the UJP with the exact location and viewing direction from wich it was recorded
  • records video from a head-mounted camera on MiniDV
  • transmits back to a Base Station in scalable resolutions
  • mobile phone is integrated, wired to an audio switcher with connectors for the headset, the external handheld microphone, the MiniDV recorder and the computer's soundboard
  • text entry is either done by a miniature keyboard or a on-screen keyboard on the optional handheld TFT touchscreen
  • software: Linux, Java, Informix database
  • motherboard: passively cooled AMD K5 at 266 MHz, 6 serial ports, 10/100 ethernet (for maintenance and data update), a 3D graphics board, a full-duplex sound board, a BT848 based video frame grabber and a 8 Gig IBM Travelstar hard disk
  • works with an Sony Glasstron or 10.4" TFT display with touchscreen
  • two Lithium Ion rechargeable batteries with 90 Wh each, power for up to 6 hours
  • one prototype exists, estimated cost $30,000
  • the 'Trimedia Consortium' was a website (as of 1999) which seems to tie the UJP together with several other companies

other approaches and base technologies:

Driving

• one way is to drive around, starting at a known basepoint, using the odometer to track your position, and manually gather information as you encounter it, with a camera, notepad, measuring devices, etc.
• this is somewhat tedious, imprecise, and limited to places you can drive a vehicle

Surveying

• generally used only for small areas
• surveying equipment is expensive, and requires training
• what are typical costs to hire a surveyor or rent equipment?  generally too high.
• Laser Technology Inc. is a leading company for laser-based surveying and mapping instruments
• Epson Locatio
  • press release:
  • ***Seiko Epson Unveils Personal Positioning Gear
    Seiko Epson will release a personal digital assistant on June 9 allowing users to position themselves.  The gadget, dubbed Locatio, can pinpoint the user's position on a map on the liquid crystal display within several meters, using a global positioning system and six ground stations set up across the country.  Seiko Epson will also start an Internet-based membership service to provide geographical and other information to users of Locatio and other mobile gear with GPS functions.
    The pocket-sized terminal, weighing only about 290 grams, also comes with a digital camera and an option for a personal handy phone system function, company officials said.   These features allow users traveling in a distant land to e-mail a friend, show their exact location on the friend's computer display and modem a snap or two of the local landscape.
    The terminal uses an energy-efficient module, developed by Seiko Epson, to allow a long operation.  The product will have open pricing, but even an upscale model with a function for the personal handy phone system will retail at less than 100,000 yen, company officials said.

Video/Photo Processing

• for buildings and other structures
• MIT City Scanning Project
  • goal: given images of an urban environment, produce a CAD model of the structures in that environment
  • uses a special camera called Argus with global positioning (GPS), heading information (IMU), and dead-reckoning (optical encoders on the wheels)
  • at each position, takes up to 70 photos which are stitched into a high-resolution hemispherical image
  • a large number of these hemispheres are gathered, called a pose image dataset
  • feature extraction and texture extraction are used to produce the output models
• Automated reconstruction of 3D scenes from sequences of images (pdf), M. Pollefeys, R. Koch, M. Vergauwen, L. Van Gool, 2000

  • claims fully automatic extraction of textured 3D models from multiple photographs, using projective reconstruction, self-calibration and dense depth estimation.

• Geometrix [geometrixinc.com, no longer online?]
  • back in 1998-2000, was working on "software-based systems which automatically generate 3D simulation models of real-world objects and scenes"
  • they call this "VideoModeling" and the product "SoftScene"
  • they implied that it would be good for digitizing structures such as buildings
  • ***Geometrix Awarded $750,000 Development Contract (February 24, 1999)
    Geometrix announced it has been awarded a research and development contract valued at $749,470 for systems that automatically generate high-resolution 3D simulation databases from video imagery tagged with GPS metadata acquired by airborne platforms. The systems will generate 3D urban terrain models at levels of detail not currently possible with satellite-based imagers. [...]
  • the product was never finished and as of early 2001, the project was inactive

Voice Recognition

• it's possible that a trained user could use natural language to rapidly input 3D scene data
• the voice recognition should be fairly doable, since we can ensure a limited, fixed vocabulary, and train the system to a specific user's voice
• CMU Sphinx Open Source Speech Recognition
  • Sphinx-2 is a real-time, large vocabulary, speaker-independent system
  • Sphinx-3 is slower but more accurate

Amateur aerial photography

• a possibility, discussed on Ben's personal site: how to elevate yourself