Geodatec

Riaan van den Dool

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Satellite Images by Geodatec

Landsat 7

SPOT 4

ASTER

Cost per Scene

L1G $600 (R4,500)

20mcol&10m pan = $2065 (R12,000)

10mcol&5m pan =

$2940 (R21,924)

2,5m pan only =

$5870 (R43,850)

$134 for 1 (R1,000)

$107 each for 2 to 10 (R800)

$ 80 each for 11 to 50 (R600)

$ 67 each for >50 (R500)

Scene Size

185km by 185km

60 x 60km, 9 = 1 LS

60 x 60 km, 9 aster = 1 LS

Spatial Resolution.

Pan=15m, VNIR=30m,

SWIR=30m, TIR=60m

Pan=5m, VNIR=20m

VNIR=15m, SWIR=30m, TIR=90m

Spectral Accuracy:

Mineral

Identification

SWIR:Can tell hydrothermally altered vs fresh rock

Can’t tell Al-OH clays (or musc) vs carbonates.

TIR: Estimate soil moisture and thermal mapping

N/A

SWIR: Can tell Mg-OH / Al-OH vs carbonates

Mineral ID-accuracy 6 x better than LS

TIR: Mineral ID 5 x better than LS.

ID silicates & phlogopites very well.

Detect spring-seepage & perched water tables v. well. Thermal to 0,3 ^oC accuracy

Spectral Accuracy:

Plants

Good

Best

Good

Stereo for DEMs

Yes

DEM vertical resolution

N/A

5m to 7m

15m

DEM cost

N/A

$7,065 (R52,780)

$670 - $1,070 (R5,000 to R8,000)

The 4 image files below shows Geodatec’s ASTER(L1B) coverage of Angola for the years 2000 to 2002. As well as an image showing the combined coverage from all 3 years. All these images have <= 20% cloud cover yet the greater part of this collection has less than 10% cover.

Images available 2000 - 2002

2000 coverage

2001 coverage

2002 coverage

Interesting facts about ASTER:

	The ASTER sensor was designed by geologists to increase spectral resolution in the geologically significant SWIR band 6 of the Landsat 4-7 sensors to more accurately identify alteration products.
	Where Landsats 4-7 have only 1 band (7) in the geologically crucial part of the Short Wave InfraRed (SWIR) wavelengths, ASTER has 6 spanning the same bandwidth.
	This implies that ASTER can identify a mineral’s spectral signature 6 times more accurately than Landsat 7 at the same 30m spatial resolution. This is why ASTER can differentiate between Mg-OH or Al-OH containing alteration products and carbonates.
	Where Landsats 5-7 have only 1 band (6) in the Thermal InfraRed (TIR) wavelengths, ASTER has 5, measuring land surface temperature readings to within 0,3^oC accuracy.
	ASTER’s TIR bands can be used in conjunction with SWIR data to very accurately delineate silicates, especially phlogopites.
	Though ASTER is somewhat more expensive than Landsat 7 data, (Landsat = $600 / ASTER = $963), the spectral signature identification of mineral spectra is about 6 times more accurate than Landsat could ever be.