Four Band Multispectral High Resolution Image Mosaic of the Colorado River Corridor, Arizona - 2021

In May 2021, the Grand Canyon Monitoring and Research Center (GCMRC) of the U.S. Geological Survey’s (USGS), Southwest Biological Science Center (SBSC) acquired airborne multispectral high resolution data for the Colorado River in Grand Canyon in Arizona, USA. The imagery data consist of four bands (Band 1 – red, Band 2 – green, Band 3 – blue, and Band 4 – near infrared) with a ground resolution of 20 centimeters (cm). These image data are available to the public as 16-bit GeoTIFF files, which can be read and used by most geographic information system (GIS) and image-processing software. The spatial reference of the image data are in the State Plane (SP) map projection using the central Arizona zone (FIPS 0202) and the North American Datum of 1983 (NAD83) National Adjustment of 2011 (NA2011). The airborne data acquisition was conducted under contract by Fugro Earthdata Inc (Fugro) using two fixed wing aircraft from May 29th to June 4th, 2021 at flight altitudes from approximately 2,440 to 3,350 meters above mean sea level. Fugro produced a corridor-wide mosaic using the best possible flight line images with the least amount of smear, the smallest shadow extent, and clearest, most glint-free water possible. The mosaic delivered by Fugro was then further corrected by GCMRC for smear, shadow extent and water clarity as described in the process steps of this metadata and for previous image acquisitions in Durning et al. (2016) and Davis (2012). 47 ground controls points (GCPs) were used to conduct an independent spatial accuracy assessment by GCMRC. The accuracy calculated from the GCPs is reported at 95% confidence as 0.514 m and a Root Mean Square Error (RMSE) of 0.297 m.

References:
Durning, L.E., Sankey, J.B., Davis, P.A., and Sankey, T.T., 2016, Four-band image mosaic of the Colorado River corridor downstream of Glen Canyon Dam in Arizona, derived from the May 2013 airborne image acquisition: U.S. Geological Survey Data Series 1027, https://doi.org/10.3133/ds1027.

Davis, P.A., 2012, Airborne digital-image data for monitoring the Colorado River corridor below Glen Canyon Dam, Arizona, 2009—Image-mosaic production and comparison with 2002 and 2005 image mosaics: U.S. Geological Survey Open-File Report 2012–1139: https://pubs.usgs.gov/of/2012/1139.

2021年5月，美国地质调查局（U.S. Geological Survey, USGS）西南生物科学中心（Southwest Biological Science Center, SBSC）下属的大峡谷监测与研究中心（Grand Canyon Monitoring and Research Center, GCMRC），针对美国亚利桑那州大峡谷内的科罗拉多河获取了机载多光谱高分辨率数据。
该影像数据包含4个波段（波段1为红光、波段2为绿光、波段3为蓝光、波段4为近红外光），地面分辨率达20厘米（cm）。
这些影像数据以16位GeoTIFF格式对外公开，绝大多数地理信息系统（Geographic Information System, GIS）及图像处理软件均可读取并使用该数据。
影像数据的空间参考采用亚利桑那州中部带（FIPS 0202）的州平面（State Plane, SP）地图投影，以及1983北美大地基准面2011年国家平差（North American Datum of 1983 (NAD83) National Adjustment of 2011, NA2011）作为基准。
本次机载数据采集工作由Fugro Earthdata Inc.（Fugro）承接合同，于2021年5月29日至6月4日期间使用2架固定翼飞机开展，飞行高度介于平均海平面以上约2440米至3350米之间。
Fugro采用成像质量最优的飞行航线影像，以最少的拖影、最小的阴影范围以及最清晰、无水面反光的水体影像为基准，生成了整个河道带的镶嵌影像。
Fugro交付的镶嵌影像随后由GCMRC按照本元数据所述的处理流程，以及Durning等人（2016）与Davis（2012）过往的影像处理方案，针对拖影、阴影范围及水体清晰度进行了进一步校正。
GCMRC共使用47个地面控制点（Ground Control Points, GCPs）开展独立空间精度评估。以95%置信度统计，由GCPs计算得到的空间精度结果为：点位误差0.514米，均方根误差（Root Mean Square Error, RMSE）0.297米。

参考文献：
Durning, L.E.、Sankey, J.B.、Davis, P.A. 及 Sankey, T.T.，2016年，《亚利桑那州格伦峡谷大坝下游科罗拉多河河道带四波段影像镶嵌图——基于2013年5月机载影像获取数据》：美国地质调查局数据系列1027，https://doi.org/10.3133/ds1027。
Davis, P.A.，2012年，《2009年亚利桑那州格伦峡谷大坝下游科罗拉多河河道带监测机载数字影像数据——影像镶嵌制作及与2002、2005年影像镶嵌图对比》：美国地质调查局公开文件报告2012–1139：https://pubs.usgs.gov/of/2012/1139。