Slide 1

Remote Sensing & Mineral Exploration
By Keiko Hamam & Sylvia Michael
GEOIMAGE Pty Ltd


Slide 2

Presentation Overview
• Brief introduction to Satellite Remote Sensing

• Resolutions – Spatial, Spectral, Temporal &
Radiometric
• Which satellite is best for me?
• What if my area has no archive imagery?
• What if my area of interest is constantly covered by
cloud ? - a brief introduction to Radar Data
• Case Study: The use of ALOS Imagery in Mineral
Exploration – Pakistan, including
• How to collect or supply GCP’s
• Orthorectification
• DEMs from Satellite Imagery
• Accuracy of Data
• Software
• Questions


Slide 3

Remote Sensing Introduction

• Satellites capture imagery as digital raster datasets
• Electro-optical sensors capture energy in different
electromagnetic wavelengths or bands from the visible, near
infrared, short-wave infrared and thermal infrared
• Different ground covers reflect or absorb energy in different
wavelengths


Slide 4

Remote Sensing Introduction - Useful Bands

Visible Blue:(0.450.52 um)
Best penetration
for clear water,
poor penetration
through haze

Near Infra Red (NIR): (0.77-1.30 um)
Determines biomass content,
delineates water bodies

Visible Green:
(0.52-0.60 um)
Vegetation vigour
assessment
Visible Red: (0.63-0.69 um)
Vegetation discrimination, high iron
oxide reflectivity

Short Wave Infra Red (SWIR): (1.306.00 um) Determines soil moisture
content, discrimination of rock types,
hydrothermal clay mapping


Slide 5

Remote Sensing Introduction - Resolutions
• SPATIAL
• SPECTRAL
• TEMPORAL

• RADIOMETRIC


Slide 6

Spatial Resolution
• The smallest feature that is distinguishable on an image is
determined by the spatial resolution, the XY dimensions of each
pixel

© Space Imaging 2003

© CNES 2004


Slide 7

Spatial Resolutions

SPOT 5 10-metre false colour left, 5-metre panchromatic right
© CNES


Slide 8

Spatial Resolutions

SPOT 5 5-metre panchromatic left, 2.5-metre panchromatic right
© CNES


Slide 9

Spatial Resolutions

SPOT 5 10-metre false colour left, 2.5-metre pan-sharpened pseudo-natural
colour right
© CNES


Slide 10

Spectral Resolution
• Spectral Resolution refers to the number of different

electromagnetic wavelength bands recorded by the
sensor
Panchromatic or black and
white imagery is acquired by a
digital sensor that measures
energy reflectance in one wide
portion of the electromagnetic
spectrum. For most current
panchromatic sensors, this
single band usually spans the
visible to near-infrared part of
the spectrum.


Slide 11

Spectral Resolution

Multispectral imagery is
acquired by a digital sensor that
measures reflectance in a
number of bands. Current
optical multispectral remote
sensing satellites can
simultaneously measure
reflectance in three to fourteen
different bands.


Slide 12

Spectral Resolution
RGB
Landsat
321

RGB
Landsat
432

RGB
Landsat
543


Slide 13

Spatial and spectral resolutions of commonly used highand medium- resolution electro-optical satellites
QuickBird

0.61m Pan (Visible to NIR), 2.44m Multi (B, G, R, NIR)

IKONOS

0.82m Pan (Visible to NIR), 3.28m Multi (B, G, R, NIR)

SPOT 5

2.5m Merged Pan (Visible), 5m Pan (Visible),
10m Multi (G, R, NIR, SWIR)

ALOS

2.5m PRISM (Visible to NIR), 10m AVNIR-2 (B, G, R, NIR)

SPOT 4

10m Pan (Visible), 20m Multi (G, R, NIR, SWIR)

SPOT 2

10m Pan (Visible), 20m Multi (G, R, NIR)

ASTER

15m 3 bands VNIR, 30m 6 bands SWIR, 90m 5 bands TIR

Landsat 7

15m Pan (Visible to NIR), 30m Multi (B, G, R, NIR, 2 bands
SWIR), 60m TIR

Landsat 5

30m Multi (B, G, R, NIR, 2 bands SWIR), 60m TIR


Slide 14

Temporal Resolution
• Temporal resolution is defined by the revisit

capabilities of the satellite

For example, Landsat 5 and 7 revisit the same
location every 16 days. Off-nadir viewing satellites,
including IKONOS, QuickBird and SPOT can be
programmed to revisit a location every few days.


Slide 15

Temporal Resolution

29 November 2001

21 December 2001


Slide 16

Temporal Resolution

30 December 1999

25 June 2001


Slide 17

Temporal Resolution

Change in Band 7


Slide 18

Radiometric Resolution
• Radiometric resolution is defined by the number of

greyscale values recorded in each band by the sensor
For example, ALOS, SPOT and Landsat have 8-bit or
single byte data. IKONOS and QuickBird have 11-bit
data.


Slide 19

Radiometric Resolution
8 Bit – 256 shades of grey

11 Bit – 2048 shades of grey

8 Bit imagery – suitable for GIS applications
11 Bit Imagery – suitable for Remote Sensing + Processing applications


Slide 20

Which satellite is best for me?
Questions to consider:
Regional exploration, prospect exploration or mine
site planning?
Amount of vegetation cover?
Suitability of age of archived imagery?
Availability of imagery?


Slide 21

Applications of high resolution imagery
• Base maps for planning of prospect exploration and
development work and mine site planning
• Planning of access roads and utilities into remote locations
• Targeting prospect areas for further exploration based on
topographic features
• Identification of previous exploration work
• Seismic planning and field operations

• Detailed identification of drainage for geochemical sampling
• Production of high-resolution digital elevation models


Slide 22

Applications of medium resolution imagery
• Regional overview of large areas
• Mapping of major geologic units
• Determination of regional structures

• Mapping recent volcanic surface deposits
• Spectral processing using Landsat and ASTER
• Extensive archive of imagery, particularly Landsat

• Small cost for large area coverage
• Production of medium-resolution digital elevation models


Slide 23

What if my area has no archive imagery?
Satellites available for programming:
• SPOT 2, 4 and 5
• IKONOS

• QuickBird
• Radarsat


Slide 24

What if my area is constantly covered by cloud?
Electro-optical sensors are passive imaging instruments that
measure electromagnetic energy emitted by the sun and
reflected off the Earth’s surface.
Synthetic Aperture Radar (SAR) sensors actively transmit a
radar signal in the microwave portion of the spectrum and
measure the strength and other characteristics of the return
signal reflected off the Earth’s surface. Because SAR is active
and operates in longer wavelengths, it can acquire images
through cloud, fog, haze and darkness.


Slide 25

What if my area is constantly covered by cloud?

SAR sensors measure the roughness of the surface compared
to the radar wavelength transmitted.
The most common wavelengths used are L-band or 235 mm
(JERS and PALSAR) and C-band or 56 mm (Radarsat, ERS and
Envisat).


Slide 26

What if my area is constantly covered by cloud?

PALSAR image of Darwin

Landsat 7 image of Darwin


Slide 27

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
At Koh-i-Sultan, Lake Resources is exploring an
extensive system of intensely altered volcanics on
the margin of an extinct caldera in a Quaternary age
compound andesitic stratovolcano.


Slide 28

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Aims:
• 5-metre DEM contours to plan access for a drill rig
• Stereo hardcopy for interpretation at 1:25,000
scale
ALOS data purchases included:
• 10-metre AVNIR-2 acquired 2 October 2006
• 2.5-metre PRISM triplet i.e. backward, nadir and
forward-looking, acquired 17 August 2006


Slide 29

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan

ALOS AVNIR-2 acquired
2 October 2006

Visible bands shown in
blue, green, red
No geometric correction
applied


Slide 30

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan

ALOS PRISM acquired
17 August 2006

Forward, nadir,
backward
No geometric correction
applied


Slide 31

From raw to end product – Collection of Ground
Control
• Most types of raw satellite imagery require some form of
geometric correction or rectification so that the imagery will
correspond to real world map projections and coordinate
systems

• Geometric rectification improves the horizontal positional
accuracy of the imagery by warping the data to match
identifiable features (Ground Control Points) from coordinated
imagery or airphotos, maps, vectors or dGPS points
• Each ground control point should be identifiable as a single
pixel on the image to be rectified


Slide 32

From raw to end product – Collection of Ground
Control

A good spread of ground control points within each
individual scene and in overlapping areas will provide a
good rectification result.


Slide 33

From raw to end product – Rectification and
Orthorectification
• For areas where there is undulating topography, or if the
imagery has been captured at a high angle to the vertical, or
very high accuracy is required, orthorectification is necessary
• Orthorectification is rectification that incorporates a digital
elevation model (DEM) to correct for distortions due to
capture angle and topographic relief
• Orthorectification is also recommended for pan-sharpening
imagery where the higher resolution panchromatic data is not
captured in conjunction with the lower resolution multispectral


Slide 34

From raw to end product – Rectification and
Orthorectification

An accurate and detailed DEM will improve the internal
locational accuracy of each pixel.


Slide 35

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
• Accurate ground control was only available
for the immediate area of the caldera
• Systematic orthorectification of the nadir
PRISM using the Geocover Landsat 7 Pan and
the Shuttle Radar Topography Mission (SRTM)
DEM


Slide 36

Digital Elevation Models (DEMs) from Satellite
Imagery
• DEMs from satellite imagery

are produced by in- or crosstrack stereo

ASTER VNIR and ALOS PRISM
(right) have in-track stereo
and SPOT has cross-track
stereo.

The agile IKONOS satellite
has a combination of both inand cross-track stereo.


Slide 37

Digital Elevation Models (DEMs) from Satellite
Imagery

ASTER VNIR band 3N on left and band 3B on right showing coincident GCPs in red


Slide 38

Digital Elevation Models (DEMs) from Satellite
Imagery

Epipolar images from previous ASTER datasets, left and right


Slide 39

Digital Elevation Models (DEMs) from Satellite
Imagery

Resultant DEM before editing


Slide 40

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan

Epipolar images from backward-forward PRISM pair, left and right


Slide 41

Accuracy of Data
• The accuracy of the final DEM or imagery is very
dependent on the accuracy of the ground control in
X, Y and Z space and needs to match the spatial
resolution of the imagery
For example, Geocover Landsat 7 Pan is a good
control base for imagery with a spatial resolution of
15+ metres, as it has a quoted accuracy of +/-50
metres. System corrected IKONOS and QuickBird
both have an accuracy of +/-23 metres, excluding
terrain effects, and therefore the ground control base
should have a better accuracy than this.


Slide 42

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
AVNIR-2 Visible
Blue, Green, Red
Orthorectified full
scene
70 km by 70 km


Slide 43

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Nadir PRISM
Orthorectified full
scene
35 km x 35 km


Slide 44

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Pan-sharpened
AVNIR-2 Visible
Blue, Green, Red
Coincident Scene
35 km x 35 km


Slide 45

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Pan-sharpened
AVNIR-2 Visible
Blue, Green, Red
right half and
AVNIR-2 Blue,
Green, Red left half
~2 km by 2 km


Slide 46

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
• The systematically orthorectified ALOS nadir
PRISM was used for control of the AVNIR-2

• The pan-sharpened AVNIR-2 was shifted to
match supplied ground control over the caldera
• The accuracy of the DEM can only be
assessed using the automatically generated
drainage


Slide 47

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Resultant DEM
35 km by 35 km


Slide 48

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Resultant DEM
showing generated
drainage vectors
35 km by 35 km


Slide 49

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan

Resultant ALOS DEM with contours on the left and the SRTM DEM on the right


Slide 50

Case Study: The Use of ALOS Imagery in
Mineral Exploration, Pakistan
Using the ALOS imagery and DEM, we were able to
supply the required 2-5-metre pan-sharpened imagery,
pseudo-stereo hardcopy for interpretation at 1:25,000
scale, a 10-metre DEM and 5-metre contours. In
addition the data was found to be of better quality
than expected and exceeded our client’s expectations.


Slide 51

Software
• At Geoimage, we use, sell and support two of the
major image processing packages, ER Mapper Pro
and PCI Geomatics.
ER Mapper Pro is an intuitive desktop package for
the processing of raster imagery. The package allows
rectification of satellite imagery and orthorectification
of air photos. We use it for geocoding, image
compression and general image processing.


Slide 52

Software
PCI Geomatics is an advanced image processing
package for remote sensing, digital photogrammetry,
spatial analysis and cartographic editing. We use it
for orthorectification of satellite imagery as it models
the satellite parameters and DEM generation. For the
case study, we also used PCI for production of a flow
accumulation image from which vector drainage lines
were automatically generated.


Slide 53

SPECTRAL PROCESSING OF ASTER DATA

ASTER VNIR bands 3, 2, 1 in red, green, blue on left
ASTER SWIR bands 5+6+7+8, VNIR bands 3, 1 in red, green and blue on right


Slide 54

SPECTRAL PROCESSING OF ASTER DATA

ASTER decorrelated SWIR bands 7, 6, 5 in red, green, blue on left
Highest predicted clay minerals on an albedo image on the right


Slide 55

Thank you

www.geoimage.com.au