ClearView 2014 Brochure

STOP PRESS
ClearView
™
MYANMAR
available
MARCH
2013
ClearView
Imagery
™
GEOIMAGE
Specialists in Satellite Imagery & Geospatial Solutions
Unique Insight
Welcome to our suite of low cloud image mosaics
providing a clear view of the Earth we live on.
For many of you, trying to obtain a view beneath the clouds has been a major problem especially in areas ripe with potential
for exploration and mining. With this in mind, Geoimage has created a series of ClearView™ products designed to map the
ground that lies below the clouds.
With the successful launch of Landsat 8 on February 11, 2013, it is timely that Geoimage provide useable imagery in areas
of major potential utilising Landsat 7 & 5 satellite data. The Landsat program is the longest running exercise in the collection
of multispectral digital data of the earth’s surface from space and has built up an archive of scenes in the hundreds of
thousands. We at Geoimage have handpicked scenes from the archive which provide the lowest cloud cover and highest
quality data possible. From these we have created seamless, cloud-masked mosaics so that you can map below the clouds.
Our ClearView™ products are low cloud coverage (less than 1%), map accurate, contain 6 band Landsat data with a 15 m
resolution, high geometric accuracies and are useable down to 1:50,000 scale, which can easily be integrated into your GIS.
These products are ideal:
✜ As a backdrop in a GIS
✜ For geological and structural interpretation
✜ Land cover assessment
✜ As an overview of the entire country or region
Currently, we have 6 products in our ClearView™ range, but are constantly adding to it, so if your area is not listed below,
please contact us for further details.
✜ Papua New Guinea
✜ Colombia ✜ Burkina Faso
✜ Mongolia
✜ Peru
✜ Myanmar (available March 2013)
Geoimage is an independent specialised provider of satellite imagery and related spatial services. With more than 25
years of experience we’ve earned a reputation as a trusted and innovative industry leader. Geoimage has a core strength
in mining, with both founding directors originating from a geology background. Whilst mining remains as the major focus
for Geoimage’s services, our client base has also diversified to now comprise a significant proportion from the oil/gas,
engineering and environmental sectors.
Geoimage is recognised for technical excellence, and beyond the supply of satellite imagery and products, we also specialise
in advanced geospatial service provision. As part of our ongoing drive and strategy to remain the premier supplier of
satellite imagery and services we are constantly creating new products to meet the needs of our customers. Together with
our software products and services, our access to the widest range of commercial satellite imagery, our partnerships with
suppliers of allied topographical mapping products, and our experienced, professional technical and sales team, Geoimage
is in the strongest possible position to provide you with customised and innovative solutions to your mapping needs. We
move beyond just data supply, we provide you with essential spatial information and unique insight.
Cheers
Bob Walker
Chairman, Geoimage Pty Ltd
clearview@geoimage.com.au
GEOIMAGE
Specialists in Satellite Imagery & Geospatial Solutions
Unique Insight
Wayne Middleton
Mobile: +61 409 494 039
E:wayne@geoimage.com.au
Bob Walker
Mobile: +61 418 334 391
E:bob@geoimage.com.au
Satellites
RESOLUTION
WORLDVIEW 2
Trying to decide which is the best satellite imagery for your
application? Geoimage can help. To help, we have broken the
different types of satellites into 3 categories:
✜ VHR (Very High Resolution) — sub metre pixels
✜ High Resolution— 2.5m to 10m pixels
✜ Mid Resolution— greater than 10m pixels
and have included a list of the major satellites at the bottom of
this page.
We have also provided a diagram showing the bandwidths in the
visible to short wave infrared of the same satellites compared
with the spectral reflectance curves of the important ground
cover types.
We will perform free data searches of your area of interest. All
you need to do is provide us with enough information about your
requirements such as:
0.5/2.0m
WORLDVIEW 1
0.5m
GEOEYE 1
0.41/1.65m
QUICKBIRD
0.6/2.4m
PLÉIADES
0.5/2.0m
IKONOS
0.8/3.2m
SPOT 6
1.5/8.0m
SPOT 5
2.5/10m
PRISM
AVNIR2
ALOS
2.5/10m
SPOT 4
10/20m
ASTER
15/30m
LANDSAT LCDM
15/30m
LANDSAT 7
15/30m
60
✜ Pixel resolution
✜ Whether you require multispectral or panchromatic (black
IRON OXIDE
KAOLINITE
% REFLECTANCE
and white) images
✜ Any time constraints, do you need the latest or can we
choose scenes from the archive
✜ What you intend to use the data for
✜ What stage of the mining lifecycle you’re interested in
DRY VEGETATION
40
B
20
A
HEALTHY VEGETATION
Then provide us with a shapefile, kmz/kml file or coordinates for
your area of interest and we will do the rest.
WATER
0
B
G
R
NEAR IR
0.5
1.0
SHORT WAVE INFRARED
1.5
2.0
2.5
ELECTROMAGNETIC SPECTRUM – WAVELENGTH IN MICROMETRES
Very High Resolution Satellites
Satellite
Panchromatic Multispectral
resolution
resolution
16.4km at nadir
Min purchase
Archive/New
Capture km2
25/100
Yes
Yes
1:1500
None
17.6km at nadir
25/100
Yes
Yes
1:1500
0.5m
4 bands
15.2km at nadir
25/100
Yes
Yes
1:1500
2.44m
0.6m
resampled
4 bands
16.5km at nadir
25/100
Yes
No
1:2000
0.5m
2.0m
0.5m
resampled
4 bands
20km at nadir
25/100
Yes
Yes
1:2000
IKONOS
0.82m
3.2m
0.8m
resampled
4 bands
11km at nadir
25/100
Yes
Yes
1:2500
SkySat
0.9m
2.0m
0.9m
4 bands
8km at nadir
50
Yes
Yes (in
future)
1:2500
Worldview-2
0.5m
2.0m
WorldView-1
0.5m
No multispectral
band available
GeoEye-1
0.5m
2.0m
QuickBird
0.6m
Pléiades
Pansharpened
resolution
0.5m
Multispectral
Bands
RESOURCESAT1
available
4 or 8 bands
Swath width
LISS4
LISS3
AWIFS
Programmable Stereo
Largest
available scale
5.8m
23.4m
56m
High Resolution Satellites
SPOT 6
1.5m
6.0m
1.5m
4 bands
60kms at nadir
250/1000
Yes
Yes
1:5000
SPOT 5
2.5m or 5m
10m at nadir
2.5m
4 bands
60x60kms at nadir 20x20kms
Yes
Yes
1:7500
ALOS
Archive only
2.5m
10m
2.5m
4 bands
70x70kms
for AVNIR
(multispectral)
or 35x35kms
for PRISM
(panchromatic)
Single scene
No
Yes
1:7500
5 bands
77kms at nadir
500/3500
Yes
No
1:15 000
4 bands
60x60kms at nadir Single scene
No
No
1:30 000
OLI=30m
15m
TIR=100m
resampled to 30m
7 OLI bands
2 TIR bands
180 x 180 kms
width
Single scene
No
No
1:40 000
Pansharpened
VNIR=15m
SWIR=30m
TIR=90m
3 VNIR bands
6 SWIR bands
5 TIR bands
60km width
Single scene
Yes (excluding Yes
SWIR)
1:40 000 for
VNIR & SWIR
TM= 30m
15m
TIR=60m
resampled to 30m
6 TM bands
180 x 180kms
2 (gains) * TIR
180 x 180kms
No
No
1:40 000
Pansharpened
TM=30m
TIR=60m
resampled to 30m
6 TM bands
1 * TIR
180 x 180kms
No
No
1:80 000
RapidEye
SPOT 4
Archive only
5m
10m
20m
10m
Mid Resolution Satellites
Landsat 8
15m
ASTER
Landsat 7
Landsat 5
Archive only
15m
180 x 180kms
3
LANDSAT Satellites
WORLDWIDE
REFERENCE SYSTEM
Images from the Landsat satellites are probably the best archive of optical imagery
available for tropical regions because the program started in 1972 and there have
been satellites collecting data ever since. Details of the Landsat program can be
found on numerous sites including-
Data from the Landsat satellites is
Inclination = 98.2o
collected in a continuous stream along a
near vertical path as the satellite moves
from north to south in a descending
pass. Some thermal imagery has been Mean Solar Time
= 9.45am
collected in ascending night-time passes. (Approximate local)
The data is arbitrarily divided into nominal
scenes which are about 24 seconds of
Direction
of Travel
spacecraft time apart, corresponding
Orbit Period = 98.8 minutes
to a spacing of approximately 160km. Near polar sun synchronous orbit
The path/row designation is referred - Landsat 5 orbit pattern
to as the Landsat Worldwide Reference
System (WRS). The rows have been positioned in such a way that Row 60 coincides
with the equator. This reference system is different for Landsats 1-3 and Landsats
4-7 because of the different altitudes and inclination angles of the satellites. This
affects the spacing of the paths so Landsats 1-3 have 251 paths worldwide while
Landsats 4-7 have 233 paths.
http://landsat.gsfc.nasa.gov/ and http://landsat.usgs.gov/
Only a very brief summary is presented here.
LANDSAT PLATFORMS
Landsat Program Summary
System
Launch (End) Sensors Resolution
Landsat 1
23 Jul 72
(6 Jan 78)
22 Jan 75
(25 Feb 82)
5 Mar 78
(31 Mar 83)
16 Jul 82
(TM - Aug 93)
1 Mar 84
Landsat 2
Landsat 3
Landsat 4
Landsat 5
Landsat 6
Landsat 7
Landsat
LDCM
5 Oct 93
(5 Oct 93)
15 Apr 99
Feb 13
RBV
MSS
RBV
MSS
RBV
MSS
MSS
TM
MSS
TM
ETM
ETM+
OLI
TIRS
80
80
80
80
30
80
80
30
80
30
15 PAN
30 MS
15 PAN
30 MS
15, 30
100
Communication
Direct Downlink
with Recorders
Direct Downlink
with Recorders
Direct Downlink
with Recorders
Direct Downlink
TDRSS
Direct Downlink
TDRSS (Failed)
Direct Downlink
with Recorders
Direct Downlink
Solid State Recorders
Direct Downlink
Solid State Recorders
Altitude Revisit
(km)
Days
917
18
Equatorial
Crossing
8.30 am
917
18
9.00 am
917
18
9.30 am
705
16
9.45 am
705
16
9.45 am
705
16
10.00 am
705
16
10.00 am
702
16
10.00 am
Six Landsat satellites have now been successfully launched commencing with Landsat
1 in July 1972. All platforms have operated from a repetitive, circular, sun-synchronous,
near-polar orbit and on each day-side pass, scan a ground swath 185km wide beneath
the satellite. The first three satellites carried the Multispectral Scanner (MSS) as the
main imaging instrument with an 80m ground resolution, and the satellites had an
18 day repeat cycle. Landsats 4 and 5 have the Thematic Mapper (TM) as the main
sensor with a 30m ground resolution and had a repeat cycle of 16 days and an
equatorial crossing between 9:30 and 9:45am local time.
The Enhanced Thematic Mapper (ETM+) sensor on Landsat 7 has a 30m multispectral
ground resolution supplemented by a 15m panchromatic band. The sensor developed
a Scan Line Corrector (SLC) problem in May 2003 and this has severely limited the
usefulness of the current ETM+ data. The Landsat 5 TM instrument finally failed in
2011 after a long period of restricted collection due to power constraints and the
satellite is currently being decommissioned (January 2013).
Nominal Scene Centre
Actual image centre can vary as
much as 20km
132
Path
Orbit paths are
numbered westward,
with path number 001
passing through eastern
Greenland and South
America
Geralton
Western
Pacific
Nominal Scene Area
Actual area of nominal scene
varies according to latitude
Example of Worldwide
Reference System (WRS)
Perth
Altitude = 750km
(Nominal)
Ground Track
Australia
48
Ocean
Bundaberg
Row
Image rows are numbered
southward, beginning from
80oN latitude with row 60
closest to the equator
DATA RECEPTION
Data from all the satellites has been either directly transmitted to ground stations,
uplinked to Tracking and Data Relay Satellites (TDRSS) (landsat 4 5) or recorded
onto onboard magnetic tapes(landsats 1 2 3) or solid state memory (landsat 7) for
later transmission to ground stations in the US. The magnetic tape storage and the
uplink to the TDRSS did not last long, so as a general rule there is more archive data
available for areas within the reception cone of ground stations.
WRS Index of PNG superimposed on ClearView™
LANDSAT THEMATIC MAPPER (TM)
World Wide Ground Receiving Stations
4
The Thematic Mapper (TM) scanner which first appeared on Landsat 4 in 1982 was
designed to provide improved spectral and spatial resolution over the MSS instrument.
The basic mode of operation is similar, however the use of more sensitive detectors,
better optics and a lower orbit has enabled the collection of radiation in 7 spectral
bands, with improved ground resolution, and with data quantised to 256 intensity
levels. Data is collected using banks of 16 detectors in each band and 16 lines of
data are collected during both the forward and backward sweeps of the oscillating
mirror system.
The geometry of TM scenes is similar to MSS. Each full scene covers an area of
approximately 185km EW by 170km NS. Pixel size in bands 1 to 5 and band 7 is
30m and 120m in band 6 (60m in Landsat 7). Landsat 7 also has a 15m panchromatic
band that can be used to sharpen the other bands. TM scenes are designated by the
same Worldwide Reference System (WRS-2) as MSS data from the Landsats 4-5.
Scene centres may be moved along the satellite path to better cover an area of
interest, but cannot be moved across track edges. Allowing for the differences in orbit
parameters and scanning optics,
geometric processing of TM data is
similar to MSS. The wavelengths of
sensors on the MSS instrument were
specifically selected for agricultural
purposes, i.e. to highlight vegetation
differences. For TM, these broad
vegetation bands were subdivided
to provide more discrimination, with
an additional sensor at 2.2um added
to provide geological information.
Mirror scanning system Landsat TM
MOSAICING SLC-OFF LANDSAT ETM+ IMAGERY. Since the scan line corrector failure
on Landsat 7 ETM+ in May 2003, the data has been under-utilised because of the
problem. Geoscience Australia offers SLC-OFF Composite Products however EROS no
longer offer such a product for international data affected by the problem. Geoimage
has developed software to mosaic multiple dates of overlapping imagery to produce
as complete an image as possible. The main problem is to identify sufficient cloud
free imagery at the same approximate time of the growing season.
Thematic Mapper Wavelengths
Band
Number Wavelength (um)
Applications
1
0.45 - 0.52
(visible blue)
coastal water mapping, differentiation of soil from
vegetation, has poor penetration through haze
2
0.52 - 0.60
(visible green)
vegetation vigour assessment
3
0.63 - 0.69
(visible red)
vegetation discrimination, also has high iron oxide reflectivity
4
0.76 - 0.90
(near infrared)
determining biomass content and delineation of water bodies
5
1.55 - 1.75
(middle infrared)
vegetation and soil moisture content, differentiation of cloud
from snow
6
10.40 - 12.50
(thermal infrared)
vegetation heat stress analysis, soil moisture discrimination,
thermal mapping, has limited use as a large percentage of
thermal radiation in daytime is reflected
7
2.08 - 2.35
(middle infrared)
discrimination of rock types and hydrothermal clay mapping
8*
0.52 - 0.90
textural detail
(visible green - near infrared) * Pan band only on Landsat 7
CURRENT STATUS OF LANDSAT 7
The Enhanced Thematic Mapper (ETM+) sensor on Landsat 7 developed an instrument
malfunction on May 31, 2003 and this has severely limited the usefulness of the
current data. The problem was caused by the failure of the Scan Line Corrector (SLC),
which compensates for the forward motion of the satellite. Subsequent efforts to
recover the SLC were not successful, and the problem appears to be permanent.
Without an operating SLC, the ETM+ line of sight now traces a zig-zag pattern along
the satellite ground track. Landsat 7 ETM+ is still capable of acquiring useful image
data with the SLC turned off, particularly within the central portion of any given scene.
Landsat 7 ETM+ therefore continues to acquire image data in the “SLC-off” mode.
The SLC-off impacts are most pronounced along the edge of the scene and gradually
diminish toward the center of the scene. The middle of the scene (approximately
22 kms) contains very little duplication or data loss.
Landsat 7 ETM+ Path 99 Row 64 March 11, 2008. Bands 543 in RGB. Example of an SLC-Off
scene which are available May 2003 to the present. SLC Composite imagery produced from
several dates are available fro Geoscience Australia however such products are no longer
available from EROS. Geoimage can produce SLC-Off composite imagery where data exists
(See the following page for an example).
Image A. Two dates of SLC-off Landsat ETM+ imagery B741 collected on 12 Oct 2004 and
05 September 2008. Image B. After matching and mosaicing.
LANDSAT DATA CONTINUITY MISSION
The Landsat Data Continuity Mission (LDCM), a collaboration between NASA and the
USGS, will provide moderate resolution worldwide imagery in a similar mode to the
earlier Landsat sensors. The satellite launched on the 11th February, 2013 and the
sensors onboard represent evolutionary advances in technology and performance
compared to the earlier sensors and will result in increased geometrical and
radiometric fidelity. This has been achieved with the use of push-broom sensor
architecture which replaces the earlier optical-mechanical sensors.
The LDCM satellite payload consists of two science instruments—the Operational
Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). These two sensors will
provide seasonal coverage of the global landmass at a spatial resolution of 30
meters (visible, NIR, SWIR); 100 meters (thermal); and 15 meters (panchromatic).
The spectral coverage and radiometric performance (accuracy, dynamic range, and
precision) are designed to detect and characterize multi-decadal land cover change
in concert with historic Landsat data. Coordinated calibration efforts of USGS and
NASA will again be part of the LDCM calibration strategy. The LDCM scene size will
be 185-km-cross-track-by-180-km-along-track. The nominal spacecraft altitude will
be 705 km. The ground-processing of the data is expected to result in a cartographic
accuracy of 12 m or better and includes correction for terrain effects. The 100m TIRS
data will be registered to the OLI data to create the final radiometrically, geometrically
and terrain-corrected 12-bit LDCM data products.
The OLI has two new spectral bands. Band 1 is a coastal band in the visible blue at a
shorter wavelength to the previous Band1 and aimed at providing better ocean colour
discrimination while Band 9 is tailored especially for detecting cirrus clouds to allow
recognition of cirrius contamination in other bands. The other spectral bands in the
OLI have had spectral refinements made to avoid atmosphetic absorption features
and this has been made possible by the higher signal-to-noise ratio inherent in the
push-broom architecture. The TIRS will collect data from two narrow spectral bands
in the thermal region formerly covered by one wide spectral band on Landsats 4–7.
The LDCM is expected to contribute approximately 400 scenes per day to the USGS
data archive (150 more than Landsat 7) and will increase the probability of capturing
cloud-free scenes for the global landmass.
5
Sources of Landsat Data
EROS - USGS
On April 21, 2008, the USGS announced plans to provide all archived Landsat scenes
held by the US Goverment, to the public at no charge. Newly acquired Landsat 7
ETM+ SLC-off and Landsat 5 TM images with less than 40 percent cloud cover are
automatically processed and made freely available for immediate download. The
downloadable inventory reaches back one year. Older scenes and imagery with more
than 40 percent cloud cover can still be ordered, however, delivery takes days, not
minutes. Only the L1T product is available. Previously offered USGS Landsat products
with customer-defined projection options on various media are no longer available.
The L1T correction process utilizes both ground control points (GCP) and digital
elevation models (DEM) to attain absolute geodetic accuracy. The WGS84 ellipsoid is
employed as the Earth model for the Universal Transverse Mercator (UTM) coordinate
transformation. Associated with the UTM projection is a unique set of projection
parameters that flow from the USGS General Cartographic Transformation Package.
The end result is a geometrically rectified product free from distortions related to
the sensor (e.g. jitter, view angle effects), satellite (e.g. attitude deviations from
nominal), and Earth (e.g. rotation, curvature, relief). Geodetic accuracy of the L1T
product depends on the accuracy of the GCPs and the resolution of the DEM used.
The 2005 Global Land Survey is used as the source for GCPs while the primary terrain
data is the Shuttle Radar Topographic Mission DEM.
The USGS Global Visualization Viewer (Glovis) http://glovis.usgs.gov/ is a quick
and easy online search tool for selected satellite data. GloVis provides greater data
availability, allowing the user visual access to browse images from the Landsat 7
ETM+, Landsat 4/5 TM, Landsat 1-5 MSS, MRLC, and Landsat Orthorectified data
sets, as well as Aster TIR and Aster VNIR browse images from the DAAC inventory.
Approximately 8,500 Landsat TM images were selected from each of the 1990 and
2000 epochs. The acquisition dates of these images were relative to a 1990 and 2000
acquisition baseline, and the images were either cloud-free or contained minimal
cloud cover. In addition, only TM images with a high quality ranking in regards to the
possible presence of errors such as missing scans or saturated bands were selected.
The Landsat data were orthorectified, using geodetic and elevation control data, to
correct for positional accuracy and relief displacement. Large blocks of Landsat data
were adjusted through a patented procedure that uses pixel correlation to acquire
tie-points within the overlap area between adjacent Landsat images. Ground control
points were fixed, and images projected to the Universal Transverse Mercator map
projection, using the World Geodetic System 1984 datum (WGS84). The result is
a final product with a Root Mean Square (RMS) Error of better than 50 metres in
positional accuracy.
GeoCover-Ortho Landsat mosaics are created by digitally suturing a group of
juxtaposed Landsat scenes into a single seamless digital image. Mosaics are color
(3 band) products with Bands 2, 4 and 7 in blue,green,red (BGR). The stock mosaics
have been prepared from both the 1990 and 2000 epoch GeoCover stock scenes
and are “off-the-shelf” products with the following Specifications -
✜ Worldwide coverage of the Earth’s landmass
✜ Data set size based on 5 degree (N-S) segments of standard UTM
✜ UTM projection, WGS84 datum
✜ 50 metre RMS positional accuracy
✜ 28.5 metre pixel size - 1990 epoch
✜ 14.25 metre pixel size (Pan sharpened) - 2000 epoch
✜ Contrast adjusted color composite of TM bands 2,4,7 in BGR
✜ Cubic Convolution interpolation
✜ Compressed using MrSID data compression or uncompressed GeoTIFF
✜ Geoimage has compressed with ERMapper ECW compression.
✜ Load&Go GIS compatible
Examples of the 1990 and 2000 GeoCover Mosaics over PNG are shown below
however they are not very useable because of the amount of cloud cover.
USGS Global Visualisation Viewer (Glovis) displaying a landsat 4-5 search over Papua
New Guinea.
GEOSCIENCE AUSTRALIA
The Earth Observation Group (previously known as ACRES) at Geoscience Australia
have been collecting imagery over Australia and Papua New Guinea since The
Australian Landsat Station was established in 1979. The EOG archive over Papua New
Guinea consists of MSS imagery collected from Landsat 2-5 post 1979 and Landsat
TM and ETM+ collected since 1988.
The EOG previously offered a comprehensive
range of image products from the archive
and these include SLC-Off Composite
Products which combine different dates of
the post 2003 SLC-Off imagery. Since the
open distribution policy was adopted by
the USGS, EOG have limited their offerings
and details can be found at http://www.
ga.gov.au/earth-observation/satellitesand-sensors/landsat.html
1990 GeoCover Mosaic
GEOCOVER
Image of Geoscience Australia
satellite imagery reception areas.
GeoCover are a global set of orthorectified
Landsat scenes compiled by Earthsat Corp under the NASA Commercial Remote
Sensing program. The scenes span three epochs; 1970s using Multi Spectral
Scanner (MSS) data, 1990 using Landsat 4 and 5 Thematic Mapper (TM) data, and
2000 with Landsat 7 Enhanced Thematic Mapper (ETM+). The dataset is unique as
it provides geographically accurate record of the earth’s surface spanning 30 years
at pixel resolutions from 14.25m to 80m and is ideally suited to scientific research
and educational activities. Full details of date selection, orthorectification, accuracy,
access and other aspects are are described in Photogrammetric Engineering & Remote
Sensing Vol. 70, No. 3, March 2004, pp. 313322.
6
2000 GeoCover Mosaic
ClearView™
The concept of a better quality Landsat mosaic than the GeoCover mosaics was initially
prompted by our clients and was originally in equatorial areas where the cloud cover
was very high (The first mosaic produced was for Papua New Guinea - Pages 8-9).
The need here was obviously a low cloud mosaic and this is achievable for most
areas of the globe because of the large Landsat archive build up since the launch
of Landsat 4 in 1992. The ClearView™ data were ideal for structural interpretation
especially using pseudo-stereo pairs at a best scale of 1:100k (See pages 16-19).
It was not long before our clients were requesting better Landsat mosaics for other
areas where the existing mosaics had high vegetation, snow, fire-scaring, drop out
lines, and other problems as well as the cloud and shadow. This led to the current
definition of the ClearView™ Landsat mosaics as a composite of the best Landsat
data available for an area which could be used for structural interpretation and in
areas of low vegetation cover could also be used for spectral studies.
METHOD OF PRODUCTION
Many Landsat scenes in equatorial areas require composites of between 10 and 20
dates of imagery to obtain relatively cloud free imagery and of course there are areas
that have never been collected cloud free. The selection of the scenes and checking
that they are geometrically accurate is just the start of the process of mosaicing
and anyone familiar with equatorial imagery will know that the shorter wavelength
bands are affected by mist or haze so that an image which looks good as a B543
composite may not have any information content in bands 1 and 2. Most software
packages which have automated mosaicing components do not cope well with
cloud and so Geoimage wrote the programs to mosaic multiple dates of imagery.
The steps in this mosaicing process are illustrated below for the Korobo 1:100k sheet
in PNG. Image A shows the 6 dates of imagery which were used in the mosaic and
in order of use were L7 08 Dec 2002, L7 06 April 2000, L5 15 April 2006, L5 29 Sept
1991, L5 31 August 2004, L5 16 July 1987. Image B shows the cloud free section
of the same images that were used in the mosaic. Image C shows the final image
after matching and mosaicing. These techniques have been used in a more general
sense to get rid of bad lines, fire scars, and snow as well as the cloud and shadow.
Although Geoimage does not generally advocate the use of mosaiced imagery for
spectral analysis, the ClearView™ mosaicing methodology still produces useable
spectral imagery - See Mongolian examples on pages 10-11.
A
AREAS COVERED
As well as Papua New Guinea, the areas currently covered by ClearView™ imagery
are Colombia, Peru, Mongolia and Burkina Faso. Other areas are being considered
and if you are interested in an area please advise us.
PRODUCTS AND PRICING
The ClearView™ imagery is available in various size options from 250K sheets (1.5deg
by 1deg), million scale sheets (6deg by 5deg) and whole of country. The purchase
includes 6 band ERMapper BIL files as well as various 3 band ECW files. Because
the production time varies for each area depending on the number of dates that
have to be used, the pricing varies with each area so please contact us for pricing.
LICENSING
The purchaser must sign a ClearView™ License Agreement recognising Geoimage
copyright on the data. The License Agreement can be downloaded from the
Geoimage web site.
C
B
7
ClearView™ PNG
ClearView™ PNG image is a mosaic of the best available
Landsat 7 and 5 imagery covering the mainland and
all the major islands and reefs that make up the
Independent State of Papua New Guinea. Where
Landsat 7 data is used the data is pan-sharpened
with the panchromatic band to maximise the spatial
detail. Landsat 5 data is resampled to 15m to retain a
consistent pixel size.
The dates of imagery used range from 1987 to 2011
and have been selected from all seasons. While every
effort has been made to reduce the visual impact of
the differences between the scenes, still remaining are
seasonal changes due to shadowing caused by changes
in sun azimuth and elevation, differences in vegetation
during the growing season, fire scars, etc, and longer
term changes due to clearing for agricultural usage,
landslides, and migration of rivers.
The dataset is within UTM zones S54 to S56 and is
available in the relevant UTM zone or in GEODETIC. The
mosaic is available in multiples of 250k sheets (1.5deg
by 1deg) or as the full mosaic.
The total 7 band 8-bit ERMapper BIL file is 60Gb in size
and the size of an average 250k sheet is approximately
500Mb. The seventh band is a water mask band to help in the contrast enhancement
of the data. ECW files of the normal three colour band combinations i.e. B543, B741
and B321 in RGB have been prepared and will also be supplied. These files are ideal
backdrops and read directly into most GIS programs.The data will be supplied on
DVD or USB external drive depending on the size of the area ordered. Other formats
(eg GEOTIFF) are available on request.
ClearView™ PNG Bands 543 in RGB. © Geoimage™ Pty Ltd. 2011.
The yellow box outlines the Ok Tedi 250k sheet.
ClearView™ PNG B543 (RGB) colour image. Copyright Geoimage Pty Ltd.
Examples of the ClearView™ PNG B543 (RGB) imagery over the OK Tedi 1:250 000 sheet
(141 to 142.5E and 5 to 6S) with 20% local area stretch. Scale bar 30km.
8
Enlargement over the Ok Tedi mine with scale bar of 5km.
© Geoimage™ Pty Ltd. 2011.
GEOCOVER 2000
0 4080Km
GEOCOVER 1990
BOUGAINVILLE Island is the main island of the Autonomous Region of Bougainville of Papua New Guinea. The island covers an area of approximately 9000 square kilometres
and is the largest and most northerly island of the Solomon Islands Archipelago. The island has several active, dormant or inactive volcanoes which rise to 2400m. The largest
active volcano, Mount Bagana, is located in the central part of the island and can be seen smoking in both GeoCover images. South-east of Mt Bagana, the closed Panguna
open-pit copper mine is visible at the north-eastern end of a trail of tailings in the drainage.
The central image is the ClearView™ PNG mosaic of the island which has been prepared from approximately 20 dates of imagery. This is ringed by the GeoCover 1990 and
2000 mosaics of the island for comparison.
9
ClearView™ Mongolia
Tile N45-45
ClearView™ Mongolia Bands 741 in RGB
in geodetic projection. © Geoimage™
Pty Ltd.
The red grid is a 6 degree (UTM zones)
by 5 degrees of latitude and define a
set of standard tiles a few of which
have been labelled to show the
nomenclature e.g. Tile N49-40 is in
UTM zone 49 with limits of 84E to
90E and 40N to 45N.
INTRODUCTION
ClearView™ Mongolia has been prepared predominantly with Landsat 7 ETM+ with
just a few scenes of Landsat 5 in the northern vegetated areas. One of the main
aims during the preparation was to minimize the amount of snow and vegetation
in the imagery so that the final mosaic could be used for spectral processing. The
dates of the the imagery are generally from August to October. The final mosaic is
a 15m resolution 6 band 8 bit ERMapper file that was prepared in WGS84 NUTM47
and Geodetic but can be reprojected into other projections.
The complete mosaic as shown in the graphic above is approximately 140 Gb and
the 6 deg by 5 deg tiles are 8-9 Gb in UTM projection (15m) and 9-12 Gb in geodetic
(0.000135deg). The data can be purchased either as the full mosaic, as individual
6deg by 5deg tiles or by the 250k sheet (1.5deg by 1deg).
SPECTRAL PROCESSING
The original bands of the Landsat TM sensor were aimed at vegetation studies and
for the detection of clay minerals using band 7 in the Short Wave Infrared. Images
typically used for interpretation are1. three band composites in the primary colours red:green:blue.
2. ratios of the spectral bands. Ratios are used because they highlight the spectral
differences between materials and at the same time decreasing the variations
in surface brightness due to topography. For example, the ratio of bands 3/1 is
often used to highlight iron oxide and 5/7 is used to highlight clays. Before ratios
are calculated it is important to remove the effects caused by scattering of light
in the atmosphere from each band. Colour composites of three band ratios are
commonly used to highlight variation in an image.
3. LSFIT images. Most clay minerals have an absorption feature in the area covered
by Landsat TM band 7. The LSFIT technique developed by the Australian CSIRO is
a linear regression technique that compares the predicted band 7 with the actual
band 7 to identify areas of anomalously high absorption and hence infer the
presence of clays. Clays are often found in alterations zones around mineralisation
however they may also be formed during surface weathering of rock forming
minerals and alluvial concentrations of clays are common. An important step
10
in the interpretation of predicted clay “anomalies” is to examine the geological
context of the anomalies to assess the origin of the clays.
The following 5 images are typical of the images used for interpretationImage A. - Three colour composite of bands 321 - natural colour.
Image B. - Three colour composite of bands 741 with the visible blue in blue,
vegetation in green and iron oxides in red. This band combination usually has
the least correlation between bands.
Image C. - Abrams Ratio with 5/7 in red, 3/1 in green and 4/3 in blue. i.e predicted
clays in red, ferric iron in green and healthy vegetation in blue.
Image D. - Greyscale LSFIT. Highest predicted clays are in white.
Image E. - Composite prediction image with the highest 1% of predicted clays based
on b5/b7 ratio in red and highest 1% predicted ferric iron in green on a greyscale
brightness image. Note: combined predicted clay/iron areas are in yellow.
A
Tile N49-50
Tile N49-45
Tile N49-40
B
D
C
E
11
ClearView™ Burkina Faso
ClearView™ Burkina Faso Bands 741 in RGB in
geodetic projection.
© Geoimage™ Pty Ltd.
The red grid is a 6 degrees (UTM zones) by 5
degrees of latitude and define a set of standard
tiles one of which has been labelled to show the
nomenclature e.g. Tile N30-10 is in UTM zone 30
with limits of 06W to 00E and 10N to 15N. The
small magenta box corresponds to the spectral
imagery on this page and the larger magenta
box is the Houndé SE 1:100k sheet shown on
page 13.
Tile N30-10
The ClearView™ Burkina Faso Landsat
mosaic has been compiled from Landsat
7 ETM+ imagery and covers Burkina Faso
and the surrounding area. The best dates
for useable imagery in this area are after
the end of the wet season in Sept-Oct and
after the cropping has been completed
and before the farmers start to burn off
the stubble in the fields. This timing is
variable and changes from north to south
and so good consistent imagery is difficult
to obtain.
The mosaic is available in multiples
of 250k sheets (1.5deg by 1deg), as
coverage of the complete country or for
the total area that has been completed
as shown in the graphic above.
These spectral images cover a 10km by 10km
area in central Burkina Faso.
Image A. - Three colour composite of bands
321 - natural colour.
Image B. - Three colour composite of bands
741 with the visible blue in blue, vegetation
in green and iron oxides in red.
Image C. - Abrams Ratio with 5/7 in red,
3/1 in green and 4/3 in blue. i.e predicted
clays in red, ferric iron in green and healthy
vegetation in blue.
Image D. - Greyscale LSFIT. Highest predicted
clays are in white.
12
A
B
C
D
BURKINA FASO MULTICLIENT GEOLOGICAL INTERPRETATION OF PSEUDO
STEREO LANDSAT 7 ETM+ IMAGERY AND 400M AIRBORNE GEOPHYSICAL
DATA: EXRESSIONS OF INTEREST
Expressions of interest are sought for participation in a multiclient geological image
interpretation covering the granite-greenstone terrain of Burkina Faso, host to
numerous deposits and occurrences of gold, copper, nickel, manganese, graphite
and chrome.
The geological interpretation, to be undertaken by Nick Lockett & Associates in
co-operation with Geoimage, will utilise Landsat 7 ETM+ imagery generated from
Geoimage’s ClearView™ mosaic of Burkina Faso, incorporating a stereo model from
SRTM DEM. Photogeological interpretation of pseudo stereo satellite imagery will be
integrated with interpretation of 400m airborne radiometric and magnetic data to
generate solid and surface geological interpretations at 1:100,000. The stratigraphy
will be constrained and guided by ground truth information taken from existing
1;200,000 published geological mapping. The results of an orientation interpretation
covering the Houndé SE quadrant are shown below as scans of manually drawn and
coloured provisional maps. A large amount of detail of surficial and bedrock geology
can be seen on the stereo Landsat imagery. The distribution of major geological units
and structures in the orientation study departs significantly from that shown on the
enlarged published geology.
The results of the study will be supplied as fully digital map sheets in MapInfo or
ArcGIS format, covering approximately 30’x30’, with four 1:100,000 modules covering
each published 1:200,000 geological sheet.
For further inquires or to view the trial sheets in more detail contact Nick Lockett or
your nearest Geoimage office.
Preliminary hand drawn regolith map of Houndé SE 1:10,000 sheet interpreted from
pseudo-stereo Landsat B742 and airborne radiometrics
Vertical 1:100,000 scale pseudo-stereo plot of the Houndé SE sheet produced from
ClearView™ Burkina Faso Bands 742 in RGB.
Provisional hand drawn solid geology map of the Houndé SE 1:100,000 sheet
interpreted from pseudo-stereo Landsat B742 and airborne radiometrics/magnetics
SE quadrant of the published Houndé 1:200,000 scale Geological map.
E-mail: nlockett@vianet.net.au
Phone +61 (0)8 9388 6222
13
ClearView™ Colombia
Geoimage has prepared a low cloud Landsat mosaic of Colombia and is offering
this image for purchase on a multiclient basis.
This mosaic will be ideal:
✜ As a backdrop in a GIS
✜ For geological and structural interpretation
✜ For land cover assessment
✜ As an overview of the entire country or region
Characteristics of the data are:
✜ Available immediately.
✜ Seamless coverage.
✜ Less than 1% residual cloud.
✜ Available by 250k sheet up to the full mosaic.
✜ Available in multiple datums.
✜ High geometric accuracies and useable down to 1:50 000 to 1:100 000
scales.
✜ Landsat 6-band multispectral unstretched data in ERMapper BIL format.
✜ Colour images in ECW format that integrate directly into your GIS.
A. ClearView™ Colombia Bands 543 in RGB in geodetic projection. © Geoimage™
Pty Ltd. 2012. The red grid is a 6 degree (UTM zones) by 5 degrees of latitude and
define a set of standard tiles one of which has been labelled to show the nomenclature
e.g. Tile N18-00 is in UTM zone 18 with limits of 78W to 72W and 00N to 05N.
B. Examples of the ClearView™ Colombia B543 (RGB) imagery over the Segovia
District. C. Enlargement over Segovia.
C
Tile N18-00
B
14
A
ClearView™ Peru
ClearView™ Peru covers all of Peru and parts of Equador, Colombia and Brazil. The
coastal zone and the Andes were prepared with predominantly Landsat 7 ETM+
pansharpened data while the vegetation covered Amazonian basin are about 50%
Landsat 7 and 50% Landsat 5 as in this area it is very difficult to find scenes with
low cloud and without haze. Minor amount of snow remain on the mosaic and
these are predominantly areas of permanent snow cover. The mosaic includes the
6 multispectral bands at 15m resolution and is available as single or multiple tiles
of 1:250k sheets (1.5deg by 1deg), million sheet tiles (6deg by 5deg) or the whole
country mosaic. The data is available in WGS84 projection in the relevant UTM zone
or in geodetic.
It is possible to spectrally process the imagery over the Andes south of about 8deg S
however the Andes to the north of this and the Amazonian rain forest have too high
a vegetation cover for spectral work. Because of the topographic relief in the area,
structural interpretation using pseudostereo pairs works extremely well.
ClearView™ Peru Bands 741 in RGB in
geodetic projection. © Geoimage™ Pty Ltd.
The red grid is a 6 degree (UTM zones) by 5
degrees of latitude and define a set of standard
tiles of which S18-10 has been labelled to
show the nomenclature e.g. Tile S18-10 is in
UTM zone 18 with limits of 78W to 72W and
10S to 15S.
The inset images in the bottom left is the
GeoCover tile for S18-10.
Tile S18-10
15
Pseudo-Stereo Imagery
INTRODUCTION
Most geologists and geographers are familiar with air photos and the increased
information that can be obtained from viewing them in three dimensions using a
stereoscope. This information mainly relates to the ability to estimate dip angles
and to interpret structural information however it is also important in understanding
the development of the physical landscape e.g. for geochemical sampling. With
the arrival of two dimensional satellite imagery i.e. Landsat in the 1970s, scientists
learnt to rely more heavily on spectral information in their interpretations. The
launch of the ASTER satellite in 1999 saw the ability to produce large area DEMs at
relatively low cost and in 2004 the SRTM DEM became available. These DEMs were
ideal for the preparation of pseudo-stereo imagery at scales to 1:50 000 and the
recent availibity of higher resolution DEMs has led to the preparation of pseudostereo imagery at scales to 1:3 000.
Geoimage has being producing stereo imagery and DEMs for clients, particularly
in the mining and exploraton industry, for many years and has coined the name
STEREO-SATMAP for the product.
DEMS
The ability to create pseudo stereo imagery at any scale has only been possible since
the ready availability of good quality low cost DEMs. DEMS which offer large area
coverage such as the SRTM data are useful down to scales of 1:100k while DEMs
derived from ALOS PRISM, WV-1 and WV-2 stereo imagery are useful at larger scales.
STEREO PAIRS
STEREO-SATMAPs are prepared by Geoimage using inhouse developed software.
Although modelled on the stereo viewing of air-photos, the stereo imagery produced
is slightly different. Air photos have radially oriented stereo (or height induced)
distortion by virtue of the instantaneous capture of a single airphoto using a lens
system. In the pseudo stereo, the input is an orthorectified three band colour image
(or a black/white single band image) and the height offset is introduced into the
data in the east-west direction. It is normal to make a left and right stereo pair,
where the height offsets are made in equal amounts but in opposite directions as
is the case in airphotos. The amount of height offset is usually made in a linear
relationship to the range of DEM values in the image and will be dependent on the
scale of the images, the type of stereoscope used and the viewing needs of the
interpreter (the amount of the stereo offset can be fine tuned for an individual).
The normal maximum offset is 20 pixels i.e. a pixel at maximum height is offset 20
pixels while a point at minimum height is not offset.
One of the problems of a stereo left-right combination is that each image is height
distorted so that neither image will produce an undistorted interpretation. This can
be overcome by preparing a left-vertical stereo pair with double the height offset on
the left stereo image i.e. a maximum of a 40 pixel offset, and a vertical or undistorted
image containing the coordinate information. A second problem relates to the size
of the image prints and trying to position them under a stereoscope. This problem
is best handled by cutting the left stereo print into vertical strips and interpreting a
strip at a time. The vertical print can be left intact.
The digital stereo images can also be examined on a computer screen. This is most
easily performed in viewing programs such as ERMapper with the images displayed
in adjacent geolinked windows. If the windows are set up with a spacing similar
to the viewers eye separation distance, it is possible to view the stereo without a
stereoscope.
Any single band (black and white) or three-band colour composite imagery can
be used to produce the pseudo-stereo imagery. The optimum scale for hardcopy
output will depend on the pixel size of the input imagery. A good rule of thumb is
to use a multiplier of 4000 to the GSD to estimate the best scale for printing. For
example, ALOS AVNIR imagery at 10 m GSD can be printed at 1:40 000 scale. The
optimum scales for various image/DEM combinations are shown in a table on the
following page.
Ok Tedi Pseudo-Stereo Imagery - Approximate scale 1:100k
Pseudo-stereo pair - Left and Vertical of Landsat B543 Imagery (ClearView™) over the Ok Tedi Mine area. The SRTM was used for the height offset and there was a range of elevations
in the image from 330 m to 2390 m. The images have been printed with the optimum separation for stereo viewing without the need for a stereoscope. The grid on the vertical image
is at 1km spacing.
16
LEFT IMAGE
VERTICAL IMAGE
STEREO-SATMAP
Examples,
using ClearView™ Oyu Tolgoi, Mongolia
IMAGE TYPE
Possible Scales for Stereo-Satmap Prints
IMAGE RESOLUTION
DEM
BEST SCALE
(GSD in metres)
WorldView-2
GEOEYE-1
0.5 – 0.6
WV-1,WV-2,
GEOEYE-1,ALOS PRISM
1:2 000
ALOS PRISM/AVNIR
SPOTMAPS
2.5
ALOS PRISM
1:15 000
ALOS AVNIR
10
ALOS PRISM,SRTM
1:40 000
ASTER
15
SRTM
1:50 000
ClearView™
15
SRTM
1:50 000
Landsat TM
30
SRTM
1:100 000
This table sets out some examples of image/DEM combinations that can be used in the
preparation of pseudo stereo pairs but is by no means exhaustive and should be used
as a guide only.
1:100 000 SCALE STEREO-SATMAP
Prepared from ClearView™ bands 741 in RGB and using
the SRTM 90m DEM for the height offset.The print covers
60km by 60km.
1:250 000 SCALE STEREO-SATMAP
Prepared from ClearView™ bands 741 in RGB and using the SRTM
DEM for the pseudo stereo. The print covers a 1.5deg by 1deg area.
1:1 000 000 SCALE STEREO-SATMAP
Prepared from ClearView™ with bands 741 in RGB and
using the SRTM DEM for the pseudo stereo. The print covers
a standard 6deg by 5deg area.
17
Case History
Geological Interpretation
Poronggo 1:100 000 Sheet, Irian Jaya.
Using Pseudo-Stereo Landsat Composites
INTRODUCTION
Landsat Thematic Mapper Imagery and ALOS PALSAR Fine Beam Mode imagery
are an ideal base for geological mapping at 1:100 000 scale in New Guinea. Both
datasets can be integrated with the SRTM DEM and prepared as pseudo-stereo pairs
while the ALOS PALSAR can be processed as red-blue anaglyph images. Dr Colin
Nash has prepared an interpretation of the Poronggo 1:100 000 sheet in Irian Jaya
using ClearView™ imagery prepared by Geoimage as an example of the information
that can be obtained from the imagery.
Plate tectonic
setting of New
Guinea and study
area location
Field photo of area 50 km east of Poronggo (looking north). The flat jungle in the foreground is
alluvium, the nearest ridge is Pliocene molasse and dipslopes in the background are Miocene
limestone
IMAGERY
The Poronggo Sheet falls wholly within Landsat Path
104 and a ClearView™ mosaic of Rows 62 and 63 was
prepared from 8 separate date images of Landsat 5 and
7 (and included SLC-off imagery). Dates varied from
August 2000 to March 2009. The mosaic included
the 6 multispectral bands of the Landsat and was
pansharpened with the 15m pan where available.
The ALOS PALSAR Fine Beam Mode (FBM) image
was collected on 07 August 2009 in descending
mode. Pixel size of the data was 10m. The data
was orthorectified to the Landsat base using the
SRTM DEM.
The Landsat B543 and the ALOS PALSAR images Mosaic of Landsat B543 path
were prepared as 1:100k scale pseudo-stereo 104 rows 62 and 63 showing the
pairs using the SRTM DEM for the height control. outline of the Poronggo Sheet.
Poronggo 100K Sheet Landsat B543 vertical image
18
Dip directions and structures interpreted from cuesta landforms on ALOS PALSAR FBM image.
Yellow - dip directions; white bedding structures; red interpreted faults; blue interpreted fold
axes. Copyright JAXA/METI
Poronggo 100K Sheet ALOS PALSAR FBM vertical image. Area outlined in red is the area
enlarged in the figure above.
INTERPRETATION
Pseudo-stereoscopic 3-D image stereopairs made
from Landsat/SRTM and ALOS PALSAR/SRTM
image data provide a powerful tool for geological
mapping in the Papuan Fold and Thrust Belt,
which marks the deformed northern margin of
the Australian tectonic plate in Papua New Guinea
and Irian Jaya. Exposed rocks of the Papuan FTB
are mostly Mesozoic and Cenozoic platform
carbonates, sandstones and shales that weather
into distinctive morphologies; these enable
stratigraphy to be mapped and, more importantly,
allow structural facing directions to be assessed
from dip cuesta landforms.
Methodical mapping of structural cuesta landforms
and stratigraphic units over the 2,500 km2
Poronggo sheet area has been carried out as a
test study, resulting in the photogeologic map of
the area shown here. The main stratigraphic units
identified are Paleozoic ‘basement’ rocks in the
north (Aiduna Fm, unit Pa) which are intruded by
Miocene Timeka pluton (Tmpk), and separated
from the Papuan FTB by the continental-scale
Aiduna Fault, which is related to current sinistral
convergence between the northern margin of
the Australia tectonic plate and micro-continental
remnants forming the western part of Irian Jaya.
The region south of the Aiduna FZ is composed
of complexly-deformed sediments of the Papuan
FTB, which include undifferentiated Mesozoic
strata (unit JK), followed by Cretaceous shales
of the Piniya Fm (unit Kp), along which thinskin style detachment is shown on published
maps and cross-sections. Sandstones of the Late
Cretaceous Ekmai Fm (unit Kue) are overlain by
well-exposed, interbedded Paleogene to Neogene Photogeologic interpretation map of the Poronggo sheet area, based on interpretation of 1:100,000 scale stereoscopic LANDSAT/
platform carbonates of the Waripi Fm and Faumai SRTM and ALOS PALSAR/SRTM imagery. Symbols explained in text; Qf and Qs are Quaternary cover.
Limestone; (units Ktew and Temy). These are
excellent subjects for interpretation, as are the uppermost molasse sandstone
deposits of the Buru Fm (map unit Tpb2).
Regional 1:250,000 scale Government geologic mapping of the Waghete Sheet
area was carried out jointly by the Australian BMR and Indonesian GRDC (Pigram
and Panggbean, 1989). These writers strongly favoured a thin-skin tectonic model,
with southward-verging ramp anticlines related to detachments in the Cretaceous
Piniya mudstone unit, as can be seen in cross-section A-B.
Our new structural interpretation is, however, incompatible with the model proposed
by Pigram and Panggabean, as comparison between section A-B on the one hand
and sections C-D and E-F shows. The critical structural observations are along
section C-D, where interpreted dip directions suggest that the fault to the north
of the Poronggo Anticline is a north-vergent thrust, which is strongly at variance
with the earlier model. It seems likely that deformation in this complex tectonic
environment involved not only N-S shortening, folding and thrusting of the Papuan
FTB as envisaged by previous workers, but also involved later deformation associated
with the crustal-scale sinistral Aiduna FZ and associated sub-parallel structures, along
which the earlier shortening structures may have been rotated.
CONCLUSIONS
This example illustrates the role of pseudo-stereoscopic, cloud-free Landsat and
ALOS PALSAR imagery in geological mapping of densely-forested regions such as
Papua New Guinea, where conventional photogeologic mapping ‘prompts’ such as
rock and soil spectral responses are generally obscured by vegetation. In regions
such as New Guinea, the identification of rock type on images is largely dependent
upon recognition of erosional characteristics, such as the superior resistance of clastic
sedimentary units and the development of karstic weathering on carbonate beds.
More importantly, the 3-D pseudo-stereoscopic images provide a way of interpreting
critical structural information through recognition of dip cuesta landforms, bedding
and foliation traces and the observation of fold closures and fault terminations of
stratigraphy. Because field access is extremely difficult in rugged rainforest areas,
existing geological maps and structural interpretations are often based upon widelyspaced field traverses that may miss many of these critical structural relationships.
The foregoing comments apply particularly to the southern part of New Guinea,
where geology is dominated by deformed Cenozoic plaformal sandstone/shale/
limestone sequences resting on the northern margin of the Australian Plate. The
differential erosion of these units makes them excellent subjects for photogeological
Cross-section A-B (Pigram and Panggbean, 1989), and schematic cross-sections C-D
and E-F, compiled from results of present study. Section locations are shown on the
interpretation map.
interpretation, which is extremely useful as this highly prospective belt is host to a
number of significant hydrocarbon accumulations (Gobe, Hides) and major porphyry
Cu/Au deposits (Grasberg, Ok Tedi, Porgera). It should be noted, however, that
significant regions exist in the northern part of New Guinea which are underlain by
accreted belts of metamorphic and volcanic rocks as well as obducted oceanic crust.
These regions are far more difficult to interpret owing to lithologic homogeneity.
19
Geoimage is Australia’s leading provider of Satellite Imagery and Geospatial Services
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requiring a spatial context, either as a reference or from which to extract derived information.
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