Digital orthophotography acquired during a tracer experiment on the Missouri River near Columbia, MO, on May 5, 2021

This child data release provides the information needed to download from the USGS EarthExplorer portal digital orthophotos acquired during a tracer experiment performed on the Missouri River near Columbia, Missouri, on May 5, 2021. One of the primary goals of this tracer experiment was to assess the feasibility of inferring concentrations of a visible dye (Rhodamine WT) from various types of remotely sensed data in a large, highly turbid natural river channel. Previous research on remote sensing of tracer dye concentrations has focused on clear-flowing streams, but the Missouri River is much more turbid. As a result, the effect of the dye on the reflectance of the water could be obscured by the effects of suspended sediment on reflectance. This experiment thus provided an initial test of the potential to map dye concentrations from remotely sensed data in more turbid rivers like the Missouri.

The experiment involved introducing a pulse of Rhodamine WT dye into the channel at an upstream transect and then observing the dispersion of the dye along the river using various in situ and remote sensing instruments. A flight contractor, Surdex Corporation, was enlisted to acquire digital orthophotography of the Missouri River area near Columbia MO, spanning the approximately 7 mile reach of the channel from river miles 176-183, during the experiment. Eight lines were flown starting around 9 am and flown 10 to 20 minutes apart, ending at 11:25 am central standard time. The images were captured with a Leica ADS100 Digital Mapping Camera. All survey ground control was also acquired and processed by Surdex, imagery was controlled using Airborne GPS/IMU technology on board the aircraft at the time of acquisition and processed against a stationary GPS base station.

Four band digital imagery was processed and triangulated and then the imagery was fully orthorectfied and moaicked for 10cm digital orthophotography delivered as 4-band tiles. The resulting data set consists of orthophotos with a 10 cm pixel size. Surdex Corporation used the raw imagery to produce high resolution 10 cm 4-band (red, green, blue, and near-infrared) orthophotos for each of eight passes over the project area of interest. Tiled deliverable products were created from a custom tiling scheme consisting of 19 tiles for each of the eight flight lines and consist of 4 band tiff files with corresponding *.tfw world files.

The data set delivered by the flight contractor was transferred to the USGS Earth Resources Observation and Science (EROS) Center for archiving and distribution via the EarthExplorer web portal at https://earthexplorer.usgs.gov. EROS also produced metadata describing the orthophotos in the file EROSmetadata.csv.

The orthophotos can can be obtained by visiting the EarthExplorer web site at https://earthexplorer.usgs.gov/and using the Entity ID field in the EROSmetadata.csv file. On the EarthExplorer home page, go to the second tab of the panel on the left, labeled Data Sets, select Aerial Imagery/High Resolution Orthoimagery, and click on Additional Criteria at the bottom. On the Additional Criteria tab, click the plus symbol next to Entity ID, enter the Entity ID value from the EROSmetadata.csv file for the tile of interest, and click on Results at the bottom. The tile should then appear in the results tab with several options represented by icons to show the footprint, overlay a browse image, or show the metadata and browse in a separate window. To download the data, click on the fifth icon from the left, which features a green download arrow pointing toward a disk drive, and click Download on the resulting pop-up to begin downloading a zip file. This zip archive contains a number of files in two subfolders. For example, for line 1, tile 10:

1) 4023644_line1_10.zip\MO\2021\202106_missouri_river_dye_columbia_mo_10cm_utm15_cnir\index001 contains shapefiles of tile layouts and exposure times for each flight line and tile and the metadata and ortho accuracy reports from the flight contractor.

2) 4023644_line1_10.zip\MO\2021\202106_missouri_river_dye_columbia_mo_10cm_utm15_cnir\vol001 has the actual image as a tif (like line1_10.tif) and corresponding *.tfw world file (like line1_10.tfw).

These files can be opened and viewed in GIS or image processing software.