PhotoSat offers a geological alteration mapping package produced using ASTER satellite photos. In larger areas with sparse vegetation, ASTER photos are used to map opal/chalcedony, total silica, kaolinite, jarosite, sericite, chlorite, calcite and many other minerals for epithermal gold and silver and porphyry copper exploration.

Alteration Minerals To Be Mapped

PhotoSat’s ASTER alteration mineral mapping package includes the minerals listed below, depending on the presence of alteration minerals on photo visible outcrops and subcrops. 

  • 12.5 m Opal/Chalcedony
  • 12.5 m Calcite
  • 12.5 m Chlorite/Epidote (note: PhotoSat cannot differentiate between chlorite and epidote minerals with ASTER photos)
  • 12.5 m Alunite
  • 12.5 m Kaolinite
  • 12.5 m Sericite (as Sericite is a hydrothermal alteration of orthoclase or plagioclase feldspars that may consist of each, or a combination of, Muscovite, Illite, and Paragonite, ASTER cannot differentiate between these micas)
  • 12.5 m Buddingtonite
  • 12.5 m Iron Oxide Gossans
  • 12.5 m Hematite
  • 12.5 m Goethite
  • 12.5 m Jarosite
  • 75.0 m All Silica

PhotoSat cannot differentiate between these minerals (below) with ASTER photos:

  • Muscovite, Paragonite and Illite
  • Chlorite and Epidote
  • Chalcedony and Opal

ASTER Report and Image Deliverables

  • All alteration minerals as 12.5 m (75 m for silica) RGB Geotiff files (distinguishing areas of possible and probable alteration minerals with a sliding blue (possible) to red (probable) colour scale)
  • Up to 12 ESRI Shapefile polygons outlining probable areas of all alteration minerals detected
  • ASTER Alteration Mapping Report: The report summarizes the alteration mineral processing results. This is not a Geological Interpretation nor an Exploration Targeting Report.​ The report is intended as a resource for qualified mineral exploration geologists.
  • Context Images:
    • Geology enhanced colour image
    •  Vegetation intensity
    • Greyscale image

Advanced Offering

Spectral matching: Spectral matching uses the spectral signature of a pixel to look for other similar pixels. If there is an outcrop of significant interest, we can analyze the spectral signature of a pixel related to that outcrop and provide a map of other pixels in the ASTER scenes that are similar. We can work with only the exact location of the outcrop, and this process is more efficient if we are provided with photographs and a detailed geologic description of the outcrop.

PhotoSat ASTER Alteration Technical Specifications

MAP PROJECTION: UTM, Others on request
DATUM: WGS84, NAD27, NAD83 – Others on request
RASTER FORMAT: Alteration and Colour Images: GeoTIFF
VECTOR FORMAT: Alteration minerals: ESRI Shapefiles (polygon)
PIXEL SIZE: Color =12.5m, alteration=12.5m, silica=75m


  • Geology enhanced colour image
  • Vegetation intensity
  • Greyscale image
15m 12.5m
  • Opal/Chalcedony
  • Calcite
  • Chlorite/Epidote
  • Alunite
  • Kaolinite
  • Sericite
  • Buddingtonite
  • Iron Oxide Gossans
  • Hematite
  • Goethite
  • Jarosite
30m 12.5m
  • Silica Zones
90m 75m