Abstract: It is well known that CO$-2$/ laser reflectances of natural surfaces containing certain minerals, notably quartz, feldspar and kaolinite, exhibit differential reflectance features in the 9 - 11 $mu@m mid-infrared spectral range. The use of off-normal reflectance ratios using measurements at four CO$-2$/ laser wavelengths to differentiate between various types of soil surfaces has been established. Off-normal reflectance ratios are observed to be relatively independent of incidence angle compared to ratios computed at normal incidence, which makes them suitable for field remote sensing applications. Road surface materials, such as concrete and asphalt, contain large quantities of quartz, and as such exhibit reflectance characteristics similar to soils. Our measurements indicate that it is, nevertheless, possible to discriminate between road and soil surfaces using off-normal reflectance ratios. Discrimination from soil surfaces is better for concrete compared to asphalt.!9
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