3D Mineral mapping of Queensland - Version 2 ASTER and related geoscience products

The digital 3-dimenional (3D) mineral mapping suite of Queensland comprises ~20 “standardized” products at the spectral resolution of the ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) sensor and generated from publicly-available satellite, airborne, field and drill core spectral data spanning the visible near infrared (VNIR; 0.4 to 1.0 µm), shortwave infrared (SWIR; 1.0 to 2.5 µm) and thermal infrared (TIR; 7.5 to 12.0 µm) wavelength regions, including:
1. Satellite ASTER maps at both 30 m and 90 m pixel resolution with complete coverage of the state of Queensland, i.e. 1.853 million km²;
2. Airborne HyMap maps at ~5 m pixel resolution with a coverage of ~25,000 km2 from areas across north Queensland;
3. Field point samples (~300) from the National Geochemical Survey of Australia (NGSA) collected from a depth of 0-10 cm of flood overbank sediments;
4. Drill-core profiles (~20) of the National Virtual Core Library (NVCL) selected from the area around the Georgetown seismic line (07GA-IG2).
Key to the processing of the remote sensing data-sets (ASTER and HyMap) was the implementation of unmixing methods to remove the effects dry and green vegetation. This unmixing was not applied to the Australian ASTER geoscience maps released in 2012 (called here Version 1 or V1) resulting in extensive areas with little/no mineral information because of the need to apply masks. The vegetation unmixing methods used in the Version 2 (V2) processing of the ASTER and HyMap imagery has resulted in very few areas without coherent mineral information.
The resultant V2 “mineral group” products were designed to measure mineral information potentially useful for mapping: (i) primary rock composition; (ii) superimposed alteration effects; and (iii) regolith cover. These V2 products may assist in mapping soil properties and groundwater conditions. However their relatively low spectral resolution (based on ASTER’s 14 VNIR-SWIR-TIR bands) means that they do not provide the high level of mineralogical detail available from hyperspectral systems (>100 spectral bands), like HyMap and the HyLogger. Nevertheless, the relatively low spectral resolution of ASTER means that all other sensor data can be spectrally resampled to that resolution. Furthermore, the ASTER global data archive, which now spans entire Earth’s land surface

昆士兰州数字化三维（3D）矿物填图套件包含约20份“标准化”产品，其光谱分辨率匹配ASTER（先进星载热发射和反射辐射计，Advanced Space-borne Thermal Emission and Reflection Radiometer）传感器，数据源自公开可用的卫星、航空、野外及钻探岩芯光谱数据，覆盖可见近红外（Visible Near Infrared，缩写VNIR；0.4~1.0 µm）、短波红外（Shortwave Infrared，缩写SWIR；1.0~2.5 µm）及热红外（Thermal Infrared，缩写TIR；7.5~12.0 µm）波段范围，具体包括：
1. 分辨率为30 m与90 m的卫星ASTER填图产品，完整覆盖昆士兰州全域（面积185.3万km²）；
2. 像素分辨率约5 m的航空HyMap填图产品，覆盖昆士兰州北部区域约2.5万km²；
3. 取自澳大利亚国家地球化学调查（National Geochemical Survey of Australia，缩写NGSA）的野外点样本（约300个），采集自河漫滩沉积物0~10 cm深度处；
4. 取自乔治敦地震测线（07GA-IG2）周边区域的国家虚拟岩芯库（National Virtual Core Library，缩写NVCL）钻探岩芯剖面（约20个）。

对遥感数据集（ASTER与HyMap）的处理核心在于采用光谱解混方法去除干燥与绿色植被的干扰。2012年发布的澳大利亚ASTER地球科学填图产品（本文中称为版本1，即V1）未应用该解混流程，因此存在大量区域因需使用掩膜而几乎无有效矿物信息。而在ASTER与HyMap影像的版本2（V2）处理中采用的植被解混方法，使得几乎不存在缺乏连贯矿物信息的区域。

最终生成的V2“矿物组”产品旨在提取可用于矿物填图的潜在有用信息：(i) 原生岩石组分；(ii) 叠加蚀变效应；(iii) 风化盖层。此类V2产品可辅助土壤属性与地下水条件填图。不过其相对较低的光谱分辨率（基于ASTER的14个VNIR-SWIR-TIR波段）意味着无法提供高光谱系统（如HyMap与HyLogger）所能实现的高精度矿物学细节。但ASTER较低的光谱分辨率特性，使得所有其他传感器数据均可被光谱重采样至该分辨率。此外，ASTER全球数据档案现已覆盖地球全部陆地表面。