Presentation on theme: "Remote Sensing & Mineral Exploration"— Presentation transcript:
1Remote Sensing & Mineral Exploration By Keiko Hamam & Sylvia MichaelGEOIMAGE Pty Ltd
2Presentation Overview Brief introduction to Satellite Remote SensingResolutions – Spatial, Spectral, Temporal & RadiometricWhich 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 DataCase Study: The use of ALOS Imagery in Mineral Exploration – Pakistan, includingHow to collect or supply GCP’sOrthorectificationDEMs from Satellite ImageryAccuracy of DataSoftwareQuestions
3Remote Sensing Introduction Satellites capture imagery as digital raster datasetsElectro-optical sensors capture energy in different electromagnetic wavelengths or bands from the visible, near infrared, short-wave infrared and thermal infraredDifferent ground covers reflect or absorb energy in different wavelengths
4Remote Sensing Introduction - Useful Bands Visible Blue:( um) Best penetration for clear water, poor penetration through hazeNear Infra Red (NIR): ( um) Determines biomass content, delineates water bodiesVisible Green: ( um) Vegetation vigour assessmentShort Wave Infra Red (SWIR): ( um) Determines soil moisture content, discrimination of rock types, hydrothermal clay mappingVisible Red: ( um) Vegetation discrimination, high iron oxide reflectivity
10Spectral ResolutionSpectral Resolution refers to the number of different electromagnetic wavelength bands recorded by the sensorPanchromatic 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.
11Spectral ResolutionMultispectral 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.
13Spatial and spectral resolutions of commonly used high- and medium- resolution electro-optical satellitesQuickBird 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 m 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 TIRLandsat 7 15m Pan (Visible to NIR), 30m Multi (B, G, R, NIR, 2 bandsSWIR), 60m TIRLandsat 5 30m Multi (B, G, R, NIR, 2 bands SWIR), 60m TIR
14Temporal ResolutionTemporal resolution is defined by the revisit capabilities of the satelliteFor 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.
15Temporal Resolution29 November 200121 December 2001
18Radiometric Resolution Radiometric resolution is defined by the number of greyscale values recorded in each band by the sensorFor example, ALOS, SPOT and Landsat have 8-bit or single byte data. IKONOS and QuickBird have 11-bit data.
19Radiometric Resolution 8 Bit – 256 shades of grey11 Bit – 2048 shades of grey8 Bit imagery – suitable for GIS applications11 Bit Imagery – suitable for Remote Sensing + Processing applications
20Which 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?
21Applications of high resolution imagery Base maps for planning of prospect exploration and development work and mine site planningPlanning of access roads and utilities into remote locationsTargeting prospect areas for further exploration based on topographic featuresIdentification of previous exploration workSeismic planning and field operationsDetailed identification of drainage for geochemical samplingProduction of high-resolution digital elevation models
22Applications of medium resolution imagery Regional overview of large areasMapping of major geologic unitsDetermination of regional structuresMapping recent volcanic surface depositsSpectral processing using Landsat and ASTERExtensive archive of imagery, particularly LandsatSmall cost for large area coverageProduction of medium-resolution digital elevation models
23What if my area has no archive imagery? Satellites available for programming:SPOT 2, 4 and 5IKONOSQuickBirdRadarsat
24What 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.
25What 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).
26What if my area is constantly covered by cloud? PALSAR image of DarwinLandsat 7 image of Darwin
27Case 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.
28Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Aims:5-metre DEM contours to plan access for a drill rigStereo hardcopy for interpretation at 1:25,000 scaleALOS data purchases included:10-metre AVNIR-2 acquired 2 October 20062.5-metre PRISM triplet i.e. backward, nadir and forward-looking, acquired 17 August 2006
29Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan ALOS AVNIR-2 acquired 2 October 2006Visible bands shown in blue, green, redNo geometric correction applied
30Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan ALOS PRISM acquired 17 August 2006Forward, nadir, backwardNo geometric correction applied
31From 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 systemsGeometric 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 pointsEach ground control point should be identifiable as a single pixel on the image to be rectified
32From 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.
33From 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 necessaryOrthorectification is rectification that incorporates a digital elevation model (DEM) to correct for distortions due to capture angle and topographic reliefOrthorectification is also recommended for pan-sharpening imagery where the higher resolution panchromatic data is not captured in conjunction with the lower resolution multispectral
34From raw to end product – Rectification and Orthorectification An accurate and detailed DEM will improve the internal locational accuracy of each pixel.
35Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Accurate ground control was only available for the immediate area of the calderaSystematic orthorectification of the nadir PRISM using the Geocover Landsat 7 Pan and the Shuttle Radar Topography Mission (SRTM) DEM
36Digital Elevation Models (DEMs) from Satellite Imagery DEMs from satellite imagery are produced by in- or cross-track stereoASTER VNIR and ALOS PRISM (right) have in-track stereo and SPOT has cross-track stereo.The agile IKONOS satellite has a combination of both in- and cross-track stereo.
37Digital Elevation Models (DEMs) from Satellite Imagery ASTER VNIR band 3N on left and band 3B on right showing coincident GCPs in red
38Digital Elevation Models (DEMs) from Satellite Imagery Epipolar images from previous ASTER datasets, left and right
39Digital Elevation Models (DEMs) from Satellite Imagery Resultant DEM before editing
40Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Epipolar images from backward-forward PRISM pair, left and right
41Accuracy of DataThe 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 imageryFor 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.
42Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan AVNIR-2 Visible Blue, Green, RedOrthorectified full scene70 km by 70 km
43Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Nadir PRISMOrthorectified full scene35 km x 35 km
44Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Pan-sharpened AVNIR-2 Visible Blue, Green, RedCoincident Scene35 km x 35 km
45Case 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
46Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan The systematically orthorectified ALOS nadir PRISM was used for control of the AVNIR-2The pan-sharpened AVNIR-2 was shifted to match supplied ground control over the calderaThe accuracy of the DEM can only be assessed using the automatically generated drainage
47Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Resultant DEM35 km by 35 km
48Case Study: The Use of ALOS Imagery in Mineral Exploration, Pakistan Resultant DEM showing generated drainage vectors35 km by 35 km
49Case 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
50Case 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.
51SoftwareAt 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.
52SoftwarePCI 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.
53SPECTRAL PROCESSING OF ASTER DATA ASTER VNIR bands 3, 2, 1 in red, green, blue on leftASTER SWIR bands , VNIR bands 3, 1 in red, green and blue on right
54SPECTRAL PROCESSING OF ASTER DATA ASTER decorrelated SWIR bands 7, 6, 5 in red, green, blue on leftHighest predicted clay minerals on an albedo image on the right