Remote Sensing

Remote Sensing

“What is Remote Sensing?” Remote sensing defined: “… is the measurement or acquisition of some property of an object or phenomenon, by a recording device that is not in physical contact with the object or phenomenon under study (formal definition of the ASPRS ) Remote sensing is both an art and a science.”

Keywords:

•acquiring, •processing, and •interpreting

images and related data that are obtained from ground-based, air-or space-borne instruments that record the interaction between matter (target) and electromagnetic radiation. Remote Sensing: using electromagnetic spectrum to image

Platforms for remote sensing Satellite

Airplane

Balloon

Terrestrial platform

• Ground – repeat or continuous sampling – regional or local coverage – example: NEXRAD for precipitation • Aircraft – repeat sampling , any sampling interval – regional or local coverage – examples: airplanes for photographs; LIDAR for ozone and aerosols

Electromagnetic wave (light)

Electromagnetic radiation is energy consisting of an electrical (E) and magnetic (M) fields oriented at right angles of each other that travels through atmosphere at the speed of light (c) at a certain wavelength (λ)

λ

The EM Range with Respect to Different Applications

Light interaction with objects Incident radiation that reaches and interact with the Earth's surface can have any of (3) forms of interaction: • absorption (A); • reflection (R); and • transmission (T). The total incident energy will interact with the surface with proportions depending on the wavelength of the energy and the material and condition of the feature.

Spectral signatures The amount of energy that interacts with object varies with wavelength, an important property that enables identification of different substances or classes. This is called spectral signatures (spectral curves), as shown in the figure below:

Energy Interactions with the Atmosphere • Atmosphere affects not only the speed of radiation, but also its wavelength, its intensity, and its spectral distribution. • (Electromagnetic Radiation) may also be diverted from its original direction due to refraction. • Interactions include: – Refraction – Scattering – Absorption – Reflectance

Processes involved:

1. Energy Source or Illumination (A) 2. Radiation and the Atmosphere (B) 3. Interaction with the Target (C) 4. Recording of Energy by the Sensor (D) 5. Transmission, Reception, and Processing (E) 6. Interpretation and Analysis (F) 7. Application (G)

A D

B

G C

E

F

Our eyes as remote sensors

Image Interpretation Elements • Size of objects must be considered in the context of image display • Shape – refers to the general form, configuration, or outline of individual objects • Shadow (1) affords an impression of profile view and (2) reflect little light on affected areas and are difficult to discern on photographs • Tone or (hue)– relative brightness or color of objects on the image • Texture – frequency of tonal change on image • Pattern – spatial arrangement of objects • Site – topographic or geographic location determines cover • Associated relationships or context – occurrence of features in relation to others

Why then use remote sensing?

• Remote – global coverage possible • Non-intrusive and wide coverage – economical • Multiple scales – ideal for different applications • Wide spectral range – visible, infrared, thermal, microwave • Hyperspectral – more applications • Repetitive coverage – ideal for environmental monitoring

Digital Image Color Composites: Combinations

RGB:321

RGB:432

RGB:543

The First Application of Remote Sensing

Meteorological Satellites - NOAA AVHRR

NOAA AVHRR • Network of satellites • 1.1 km spatial resolution • Polar-orbiting • 5 channels (VIS~IR) • 870 km away • 3000 km swath width

TRMM (Tropical Rainfall Measuring Mission)

TRMM Characteristics • 7 sensors onboard •Ground horizontal resolution:4 km • Swath width: 220 km • Product: height of about 12 miles (20 kilometers). •The Precipitation Radar will be able to detect fairly light rain rates down to about .027 inches (0.7 millimeters) per hour

MODIS Sensor (payload in TERRA and AQUA satellites) Moderate Resolution Imaging Spectroradiometer Radiometric sensitivity: 12 bit 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm. The responses are custom tailored to the individual needs of the user community and provide exceptionally low out-of-band response. Two bands are imaged at a nominal resolution of 250 m at nadir, with five bands at 500 m, and the remaining 29 bands at 1 km. A ±55degree scanning pattern at the EOS orbit of 705 km achieves a 2,330-km swath and provides global coverage every one to two days

ERTS-1 • First Unmanned Satellite Dedicated to Multi-Spectral Remote Sensing • Renamed Landsat – The RBV (Return Beam Vidicon) consisted of three TV-like cameras which used color filters to provide multispectral bands • MSS (Multi-Spectral Scanner)

LANDSAT ETM+

LANDSAT 7 ETM • • • • • • •

“7” indicates 7th launch Sun-synchronous 7 (ETM) + 1 (Pan) channels 30-m spatial resolution (ETM) 15-m spatial resolution (Pan) 16 day revisit period swath: 185 km x 185 km

San Francisco Bay, California 2001. Image on right shows contrast of green vegetation, urbanized centers (grey color) along coastal area and the differences in water composition in the estuary. Notice the prominence of the San Andreas fault

SPOT Imagery Colors are from the French SPOT satellite imaging data in both visible and infrared wavelengths collected in February 1996. Areas of vegetation appear red and areas without vegetation appear light blue. River valleys radiate out from the summit of the volcano (upper left)

SPOT 4 • 10 & 20 meter res. (Pan & XS resp.) • 26 days orbit repetition (Sun-sync) • 3 Bands (XS), 1 Band pan with vegetation sensor • 117 km swath width (panning possible) • Stereoscopic data generation capability

IKONOS (2)

Resolution: 4m (MS) 1 m (pan) No of Bands: 4 (3 vis & 1 NIR Dynamic range: 11-bit: Orbit time: 98 m Time pass: 1030 am Revisit Period: 11 days minimum

Top right: This one-meter resolution image of Mount Pinatubo, Philippines was collected March 6, 2001 by Space Imaging's IKONOS satellite. The image features the volcano located 90 kilometers north of Manila. Once standing 1,780 meters (5,840 feet), Mount Pinatubo was dormant for 600 years until 1991 when the volcano erupted twice in June of that year.

Quickbird (by Digital Globe)

• •

•

•

Sensor Resolution & Spectral Bandwidth Panchromatic: – 61-centimeter GSD (Ground Sample Distance)at nadir – Black &White:450 to 900 nanometers Multispectral: – 2.44-meter GSD at nadir – Blue: 450 to 520 nanometers – Green: 520 to 600 nanometers – Red: 630 to 690 nanometers – Near-IR: 760 to 900 nanometers Revisit period: 1- 3.5 days

Spy satellites • A spy satellite (officially referred to as a reconnaissance satellite) is an Earth observation satellite deployed for military or intelligence applications

Radar – Radio Detection and Ranging • Radars operate both as transmitters and receivers:– they transmit energy towards the Earth’s surface – they receive only what is scattered back towards the radar – (Note that in other contexts, you can have transmitters and receivers in different places…) – they calculate distances by timing how long this takes

Banda Aceh Detail Before Debris

Banda Aceh Debris Detail

Banda Aceh Shore (Before Tsunami) Imagery collected June 23, 2004

Banda Aceh Shore Imagery acquired December 28, 2004

During and postTsunami images of Sri Lanka beach

2004 Global Temperature Anomalies

Monthly Mean Global Vegetation Index 2004

ALOS PALSAR over Southern Leyte

Observed: Feb. 24, 2006

Radar Imagery of Mt Pinatubo and Vicinity

ALOS PALSAR: Landslide monitoring

ALOS PALSAR: Oil Spill Detection

ASTER (Advanced Spaceborne Thermal Emission and Reflectance Radiometer)

ASTER sensor onboard Terra Satellite (above) • • • • • •

15 m resolution, (1st 3 bands) 30 m resolution, (mid 6 bands) 90 m resolution, (last 15 bands (VIS~TIR) 60 km x 60 km swath Selective acquisition (on request)

Top-right: Two half scenes covering the Laguna de Bay and vicinity taken January 3, 2001. Lake waters exhibit high turbidity during the dry season

Landcover classification Level 1: Example

23 Feb 2002 Landsat-7 ETM+

+ dam

Landcover classification Level 1: Example

23 Feb 2002 Landsat-7 ETM+

Classification of Shallow Seafloor

Ikonos Multispectral 08/26/2003

Classification Image

Remote Sensing in the Philippines • Still mainly based on aerial photography (black and white mostly used) • No systematic data acquisition program – Dependent on mapping projects to acquire images • We have no ground receiving station while – our neighbours, Indonesia, Malaysia, Thailand or even Viet-nam) have – Thailand will launch its own satellite (geostationary) • We have local distributors for the following products – Quickbird: GSMI – IKONOS: ? – SPOT: Certeza – Landsat: NAMRIA – ASTER: ? • ..to think that 30 years ago we were looked up to in Asia as having the most advanced technology in the region!