4. An airborne or spaceborne imaging sensor simultaneously samples
multiple spectral wavebands over a large area in a ground-based
scene.
each pixel in the resulting image contains a sampled spectral
measurement of reflectance, which can be interpreted to identify the
material present in the scene.
5. Hyperspectral sensors collect information
as a set of 'images‘
Each image represents a narrow wavelength range of the
electromagnetic spectrum, also known as a spectral band.
These 'images' are combined to form a three-dimensional (x,y,λ)
hyperspectral data cube for processing and analysis,
where x and y represent two spatial dimensions of the scene,
and λ represents the spectral dimension (comprising a range of
wavelengths)
The primary advantage to hyperspectral imaging is that, because
an entire spectrum is acquired at each point, the operator needs
no prior knowledge of the sample, and postprocessing allows all
available information from the dataset to be mined.
6. Spatial scanning (Push Broom) NGC
◦ each two-dimensional (2-D) sensor output represents a full
slit spectrum (x,λ)
◦ obtain slit spectra by projecting a strip of the scene onto a
slit and dispersing the slit image with a prism or a grating
◦ the spatial dimension is collected through platform
movement or scanning.
◦ line-scan systems are particularly
common in remote sensing
Spectral scanning
◦ each 2-D sensor output represents a
monochromatic ('single-colored'),
spatial (x,y) map of the scene
7. Non-scanning
◦ a single 2-D sensor output contains all spatial (x,y)
and spectral (λ) data
◦ HSI devices for non-scanning yield the full datacube
at once
Spatiospectral scanning
◦ each 2-D sensor output represents a wavelength-
coded ('rainbow-colored', λ = λ(y)), spatial (x,y)
map of the scene.
8. Hyperspectral imaging pushbroom spectrometers1,3,4 are currently used in several
domains in order to identify the spectral signatures of a broad range of materials in the
reflected solar energy spectrum.
The camera images the scene line by line using the a so-called "pushbroom" scanning
mode. The result can be seen as one 2d image for each spectral channel, or alternatively
every pixel in the image contains one full spectrum.
Spectrometers provide data under the form of hyperspectral cube.
A hyperspectral cube with M across-track pixels, L alongtrack pixels, and P spectral
bands is here considered.
The plane formed by the across-track and the spectral dimensions is called frame; a
frame has M spatial pixels (M columns) and P spectral pixels (P rows). Figure 1 shows
how the sensor generates such a cube.
9.
10. on-chip binning
◦ two or more spectral bands are summed up in a way that they form a unique
row channel (Figure 2). This summation is done by the hardware during
image acquisition.
◦ In general, the higher the number of binned rows (bands), the higher is the
spectral SNR.
◦ Spectral binning will reduce the number of bands.
frames are M x B matrixes, where B <= P.
Current processing systems for the above sensor schemes incorporate a frame
buffer that captures an image into memory. However, rapid detector-array
advances in resolution, frame rate, and dynamic range will soon exceed
throughput limits inherent in store-and process systems
11. The number of across-track spatial pixels is
preserved.
Whereas the bands (0,1,2) are binned to form band
(0), bands (3,4) will form band 1 and so on.
Landsat-7 Simulation uses Spectral Binning.
In general, the higher the number of binned rows
(bands), the higher is the spectral SNR.
12. Hyperspectral image-processing algorithms must be
performed on many parallel PE’s to maintain high
throughputs.
Rather than store the entire image frame the computation
must be performed as the data arrive to minimize storage
buffers.
13. Organization of a SIMD computer
architecture. Program instructions are
broadcast to every PE in the system through a
single instruction stream, and each PE carries
out the received instructions on its local data.
P0, P1, Pn, PE’s; MEM 0, MEM 1 MEM n, local
memory.
14. Block diagram of the SIMD focal-plane system.
◦ Each PE in the SIMD processor array can address a 4 3 4 array of image sensors.
◦ An ALU with an adder–subtractor and a barrel shifter.
◦ A multiply–accumulate ~MACC! unit.
◦ Three-ported general-purpose register file and special register.
◦ Sixty-four words of local memory ~a maximum of 256 words!.
◦ Communication and serial IO units.
◦ A masking unit to control PE activity.
This model permits the entire image as
projected onto many PE’s to be obtained
in a single operation.
◦ Shift unit, barrel shifter; ADC
15.
16. NASA's Earth Observing EO-1 with its
hyperspectral instrument Hyperion
implements Spatial scanning
Hyperion Data is standard HDF Version 4.1 (v5)
◦ band-interleaved-by-line (BIL) files
◦ stored in 16-bit signed integer radiance values.
Converted non-HDF format (off-line)
◦ so it is raw 16-bit signed, Little Endian
◦ Optionally unsigned 16-bit
17. Frame 256 pixels x 242 Bins (Frequency) (Push Broom)
◦ BIN 6 does not exist, 7 sets only
◦ Sensor 1 1-70 Bins; Multiplied by 0.025
◦ Sensor 2 71 – 242 Bins; Multiplied by 0.0125
◦ Freq Bin Coefficients Range: 0 - 12K counts 13.5 Bits
7 Bands of Proportional Data
◦ [242 x 7] Array of Numbers:
◦ Band Proportional Coefficients Dynamic Range = Log2 (12K-0) = 13.55 Bits
6K Frames of Data for Simulation
Derived Rqmt (Miguel) (Need to Assess Architecture)
◦ Frame Rate ~ 60 Hz
◦ Implies pixel rate = 25 Mhz
◦ Clock Rate ~ 100 Mhz
Functional (see Blk Dgm)
19. We are taking 242 Spectral Filters and mapping into the 7
Spectral Filters of LANDSAT-7
The LANDSAT Equivalent Pixel will then be 7 Rows
INj,k x PCk,o = PDj,o LANDSAT Pixel Rows
Resulting Image is a Frame of J x O or 256x7 Numbers
Plus Average Band?
20. Design Schedule is TOP priority
◦ Need to show path to deliverable configuration
Floating vs Integer MAC
◦ IEEE Floating point will let us get there faster
◦ Integer doable, but not now
IEEE 754 standard specifies a binary32 as having:
◦ Sign bit: 1 bit
◦ Exponent width: 8 bits
◦ Significand precision: 24 bits (23 explicitly stored)
Number Conversion Sequence
◦ Before or After Ping/Pong
24. Miguel identified Alpha Data XRM-ZBT
◦ provides 2 banks of between 256K and 2048K x
36-bit ZBT pipelined memory
◦ 2 RS232 ports on the front panel
25. Partitioned with Resources in Mind
◦ Miguel HW and Interfaces with SATA & Display
◦ Horace System Architecture Issues, Trades
◦ Yogi VHDL Processing Engine
