1 / 24

Lecture 9 Content

Lecture 9 Content. Near Polar orbiting earth resources satellites: SPOT LIDAR. SPOT LANDSAT system suffered three major drawbacks: Very high ground resolution is not possible with the mechanical MSS

sara-bishop
Télécharger la présentation

Lecture 9 Content

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Lecture 9 Content • Near Polar orbiting earth resources satellites: • SPOT • LIDAR

  2. SPOT LANDSAT system suffered three major drawbacks: • Very high ground resolution is not possible with the mechanical MSS • The repetition time for any one scene is quite long, 18 or 16 days per satellite. Satellites have limited operational value especially when data is needed for monitoring purposes. • Stereoscopic viewing is only possible in narrow image overlaps, and the accuracy of height estimation is low

  3. SPOT French tackled these drawbacks as follows: • It was decided to use a pushbroom scanner. Not only can modern pushbroom scanners provide high resolution, they have a longer and more reliable life expectancy, lower power requirements, and higher geometric and radiometric accuracy • Mirrors make off-nadir viewing possible which allow any area to be viewed frequently. Oblique viewing allowed for stereoscopic viewing

  4. SPOT satellite characteristics: • SPOT in the first earth resource satellite to be launched from Europe • Other characteristics of SPOT which are similar to LANDSAT • Near-polar sun synchronous orbit • Transmission of data to ground stations with the possibility of on-board recording • SPOT sensors can sense in high resolution (10m) panchromatic mode or lower resolution (20m) multispectral mode in 3 wavelengths

  5. A single SPOT scene covers a geographical area of 60 x 60 km. • Two alternative modes of imaging are possible using SPOT: • Panchromatic: black and white, with a ground resolution of 10 m • Multispectral: colour, with 20 m ground resolution acquired simultaneously in 3 bands : green, red and near infrared.

  6. In a MSS it scans the scene from side to side and reflects radiation from the ground surface onto a detector • This process is limited by the accuracy of the rotating mirror • To overcome this problem a HRV (High Resolution Visible) scanner is used in SPOT. It does not have any moving parts, instead, it records each scan line at one go by means of a line of detectors – one detector for each area sampled on the ground • Detectors are controlled by a microchip and controls 1,728 detectors on SPOT

  7. Comparison between pushbroom scanner and MSS

  8. SPOT 1 and SPOT 2 available and launched in 1985 and 1986 respectively • SPOT 1 carry two identical pushbroom scanners which are called “High Resolution Visible” (HRV) scanners • When in panchromatic mode all of the detectors are sampled with a spatial resolution of 10m • Used for mapping scales of 1:150,000 to 1:100,000 • When in multispectral mode only half of the detectors are sampled with a spatial resolution of 20m • Used for pollution monitoring to vegetation mapping

  9. SPOT ground receiving stations

  10. SPOT Panchromatic

  11. SPOT Multispectral

  12. LIDAR • Light Detection And Ranging (LIDAR) • It is a radiometer system that uses a light beam instead of a microwave radar beam (Radar) to obtain measurements of speed, altitude, direction and range of a target • Lidar is used to precisely measure distances and properties of far-away objects • Its operation is that a powerful laser transmits a short and intense pulse of light • Very high spatial resolution, for example a DEM was created of a complete coverage of the Netherlands at a spatial resolution of 1 cm (Introduction to LIDAR, 1997).

  13. Use of LIDAR for accurate determination of terrain elevations began in the late 1970’s but its use was limited due to project cost-effectiveness • One of the most successful early applications of LIDAR was in the determination of accurate water depths • Modern LIDAR acquisition makes use of a rapidly pulsing (20,000 to 50,000 pulses/sec) laser and a highly accurate clock to measure time • The principle of LIDAR is similar to that of RADAR • Further details in lecture 10

  14. LIDAR image at ground zero NY

  15. Lidar Applications • Atmospheric science - dynamics measurements: temperatures, winds, and waves- climate measurements: clouds, aerosols, and water vapor- ozone measurements: depletions and polar stratospheric clouds- high altitude trace metal measurements: sodium and potassium- pollution monitoring • Astronomy • planetary surface relief mapping (eg lidar Mars maps by NASA) • Topographic mapping • erosion monitoring • Bathymetry (under water mapping) • harbor profiling for marine safety

  16. Forest ground and canopy measurements • used to assess forest growth and health • Building and factory construction • measurements allow for precise prefabrication, improving efficiency and reducing costs • Mine shaft mapping • allows cavern monitoring for worker safety • Aircraft docking • for safe aircraft maneuvering near airport terminals • Automobile speed monitoring • a replacement for hand-held radar guns

  17. … The End …

More Related