Radar03

Radar Imaging: 

Radar Imaging GEOS 5325 Fall 2007 Dr. Stuart Murchison

Non-Imaging Radar: 

Non-Imaging Radar Radar (an acronym for "radio detection and ranging") is a device that emits and receives radio waves. The waves bounce off the targeted vehicle and are received by a recorder. The recorder compares the difference between the sent and received waves, and translates the information into miles per hour.

Non-Imaging Radar: 

Non-Imaging Radar To provide a polar-coordinate map-like display of targets, NRL originated the radar PLAN-POSITION INDICATOR (PPI)-the well-known radar scope with the round face and the sweeping hand-between 1939 and 1940. The PPI is now universally used by military and commercial interests around the world for the display of radar information for such functions as air and surface detection, navigation, air traffic control, air intercept, and object identification

Imaging Radar - General: 

Imaging Radar - General

Microwave Region: 

Microwave Region

Radar Bands: 

Radar Bands

Radar Bands: 

Radar Bands

Imaging Radar - Advantages: 

Imaging Radar - Advantages

Imaging Radar - Operation: 

Imaging Radar - Operation

Terminology: 

Terminology

How Radar Works: 

How Radar Works Microwave energy pulses (A) are emitted at regular intervals and focused by the antenna into a radar beam (B) directed downwards and to the side. The radar beam illuminates the surface obliquely at a right angle to the motion of the platform. Objects on the ground reflect the microwave energy depending on factors such as roughness and attitude. The antenna receives this reflected (or backscattered) energy (C).

How Radar Works: 

How Radar Works By measuring the time delay between the transmission of a pulse and the reception of the backscattered "echo" from different targets, their distance from the radar and thus their location can be determined. As the sensor platform moves forward, recording and processing of the backscattered signals builds up a two-dimensional image of the surface.

Radar Geometry: 

Radar Geometry

Radar Image Geometry - Shadow: 

Radar Image Geometry - Shadow

Radar Image Geometry - Shadow: 

Radar Image Geometry - Shadow

Radar Image Geometry - Shadow: 

Radar Image Geometry - Shadow

Shadow is more of a problem at far range: 

Shadow is more of a problem at far range

Radar Image Geometry - Layover: 

Radar Image Geometry - Layover

Radar Image Geometry - Layover: 

Radar Image Geometry - Layover Layover occurs when the radar beam reaches the top of a tall feature before it reaches the base. The top of the feature is displaced towards the radar sensor and is displaced from its true ground position - it 'lays over' the base. The visual effect on the image is similar to that of foreshortening.

Foreshortening: 

Foreshortening Foreshortening occurs because radar measure distance in the slant-range direction such that the slope A-B appears as compressed in the image (A'B') and slope C-D is severely compressed (C'D')

Radar Image Geometry - Shadow & Foreshortening: 

Radar Image Geometry - Shadow & Foreshortening 4,317 meters (14,161 feet) Stratovolcano Mt. Shasta, California

Target Interaction and Image Signatures: 

Target Interaction and Image Signatures

Surface Roughness: 

Surface Roughness

Radar viewing and surface geometry relationship : 

Radar viewing and surface geometry relationship Different vegetation types (e.g., desert, grasslands, forests or frozen tundra) will all have different backscatter properties. In addition, the basic reflectivity of the soil, called the "dielectric constant" will change depending on the amount of water that the soil contains. Dry soil has a low dielectric constant, so that little radar energy will be reflected. Saturated soil will have the opposite effect, and will be a strong reflector. Moist and partially frozen soils will have intermediate values.

Moisture content and electrical properties of the target : 

Moisture content and electrical properties of the target Dielectric constant is controlled by the amount of moisture content, hence, the return of radar signal is influenced by the amount of moisture in the soil and vegetation. Most common materials have dielectric constants 1-100 By affecting the absorption and propagation of electromagnetic waves, dielectric constant strongly influence the interaction of electromagnetic radiation with the terrain surface. Increasing the moisture content reduces the penetration of the radar signal beneath the soil and vegetation canopy.

Radar Speckle: 

Radar Speckle All radar images appear with some degree of what we call radar speckle. Speckle appears as a grainy "salt and pepper" texture in an image. This is caused by random constructive and destructive interference from the multiple scattering returns that will occur within each resolution cell. Speckle reduction can be achieved in two ways: multi-look processing spatial filtering. Both multi-look processing and spatial filtering reduce speckle at the expense of resolution, since they both essentially smooth the image. Therefore, the amount of speckle reduction desired must be balanced with the particular application the image is being used for, and the amount of detail required.

Airborne versus Spaceborne Radar: 

Airborne versus Spaceborne Radar Airborne radar must image over a wide range of incidence angles in order to cover a wide swath. Spaceborne radar does not require a wide range of incidence angles to cover a wide swath.

Polarization: 

Polarization

Radar Signal Polarization: 

Radar Signal Polarization Polarization of the radar signal is the orientation of the the electromagnetic field and is a factor in the way in which the radar signal interacts with ground objects and the resulting energy reflected back. Most radar imaging sensors are designed to transmit microwave radiation either horizontally polarized (H) or vertically polarized (V), and receive either the horizontally or vertically polarized backscattered energy.

Radar Signal Polarization: 

Radar Signal Polarization

Radar Polarization Example: 

Radar Polarization Example

DEM’s and Radar Interfereometry: 

DEM’s and Radar Interfereometry

DEM’s and Radar Interfereometry: 

DEM’s and Radar Interfereometry

DEM’s and Radar Interfereometry: 

DEM’s and Radar Interfereometry

Slide36: 

Dome of metamorphic rocks in the Sahara desert (Sudan) Landsat SIR-C radar

SIR-C Image of Vesuvius and Naples, Italy: 

SIR-C Image of Vesuvius and Naples, Italy Mt. Vesuvius, one of the best known volcanoes in the world primarily for the eruption that buried the Roman city of Pompeii in AD 79, is shown in the center of this radar image. The central cone of Vesuvius is the dark purple feature in the center of the volcano. This cone is surrounded on the northern and eastern sides by the old crater rim, called Mt. Somma. Recent lava flows are the pale yellow areas on the southern and western sides of the cone. It shows an area 100 kilometers by 55 kilometers (62 miles by 34 miles.)

Slide38: 

SIR-C image of Nile Paleochannel, Sudan The top image is a photograph taken with color infrared film from Space Shuttle Columbia in November 1995. The radar image at the bottom is a SIR-C/X-SAR image. The thick, white band in the top right of the radar image is an ancient channel of the Nile that is now buried under layers of sand. This channel cannot be seen in the photograph and its existence was not known before this radar image was processed. The area to the left in both images shows how the Nile is forced to flow through a chaotic set of fractures that causes the river to break up into smaller channels, suggesting that the Nile has only recently established this course. Each image is about 50 kilometers by 19 kilometers. Red = Chv; Green = Lhv; Blue = Lhh

SIR-C/X-SAR image of the Mississippi River: 

SIR-C/X-SAR image of the Mississippi River This image of the Mississippi River in Mississippi, Arkansas, and Louisiana shows regions that are prone to flooding. The image covers an area of about 23 km by 40 km. Red = Lvv; Green = Lvh; Blue = Cvv. This site along the Mississippi River lies north of Vicksburg along the Arkansas- Louisiana-Mississippi state borders. This region is characterized by rich farmland. The town in the extreme upper left is Eudora, Arkansas. The long, narrow lakes which parallel the river are called oxbow lakes, named for the U-shaped harness worn by an ox. Oxbows form when a river changes course, abandoning old channels in favor of a new course. As the river changes course, the surrounding land dries out, leaving these lakes isolated. Oxbow lakes are common in areas where rivers flow through generally flat terrain, allowing the river to easily change course. The green regions bordering the river are undeveloped forested areas.

Nov. 2002 Oil spill in Spain: 

Nov. 2002 Oil spill in Spain A damaged oil tanker off the northwest coast of Spain split in half on November 19, 2002, creating a series of large oil slicks. The image shows the oil slick with RADARSAT data. Black areas indicate the location of the slick on November 18. The land is shown using Landsat falsecolor

Radarsat Mosaic of USA (190 images): 

Radarsat Mosaic of USA (190 images)

Radar Imaging of Cities(San Francisco): 

Radar Imaging of Cities (San Francisco) This SIR-C/X-SAR image of San Francisco, California shows how the radar distinguishes between densely populated urban areas and nearby areas that are relatively unsettled. Downtown San Francisco is at the center and the city of Oakland is at the right across the San Francisco Bay. Some city areas, such as the South of Market appear bright red due to the alignment of streets and buildings to the incoming radar beam. Various bridges in the area are also visible. All the dark areas on the image are water. Two major faults are visible. The San Andreas fault, on the San Francisco peninsula, is seen in the lower left of the image. The fault trace is the straight feature filled with linear reservoirs which appear dark. The Hayward fault is the straight feature on the right side between the urban areas and the hillier terrain to the east. The image is about 42x58 km.

Archeology of Angor, Cambodia: 

Archeology of Angor, Cambodia The city houses an ancient complex of more than 60 temples dating to the 9th to 15th centuries. Today the Angkor complex is hidden beneath a dense rainforest canopy, making it difficult for researchers on the ground. The principal complex, Angkor Wat, is the bright square just left of the center of the image. It is surrounded by a reservoir that appears in this image as a thick black line. The larger bright square above Angkor Wat is another temple complex called Angkor Thom. Archeologists studying this image believe the blue-purple area slightly north of Angkor Thom may be previously undiscovered structures. In the lower right is a bright rectangle surrounded by a dark reservoir, which houses the temple complex Chau Srei Vibol. Image is 55x85km. Red=Lhh, Green =Lhv, and Blue =Chv.

Slide44: 

C-Band image of Dallas 35 km (21 miles) by 26 km (16 miles)

SIR-C/X-SAR image of Mississippi Delta: 

SIR-C/X-SAR image of Mississippi Delta The area shown is approximately 63 km by 43 km. As the river enters the Gulf of Mexico, it dumps its load of sediment, building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad red stripe running northwest to southeast down the left side of the image. The bright spots within the channel are ships. Red = Lvv; Green = Cvv; Blue = Xvv.

Slide46: 

USSR Landers Indicate Venus has a Rocky Surface Venera 9, 1975 Venera 10, 1975 Venera 13, 1982

Slide47: 

98% of the Venutian surface was mapped. Magellan finally burned up in the venusian atmosphere, in mid-October, 1994. Image at right: Blues represent the lowest surfaces followed by greens, then yellows and oranges with red being highest. High region, near the equatorial center, is Aphrodite Terra. Beta Regio, near the central left, is also elevated.