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A New GRIME2: Using an Octagon Calibration Target and Trail Camera to Measure Stream Water Level Over a 2‐Year Period.

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Title: A New GRIME2: Using an Octagon Calibration Target and Trail Camera to Measure Stream Water Level Over a 2‐Year Period.
Authors: Gilmore, Troy E., Chapman, Kenneth W., Harner, Mary J., Bajelan, Jamila, Terry, Chris, Stranzl, John E., Mittelstet, Aaron R., Chapman, Christian D., Mehrubeoglu, Mehrube
Source: Water Resources Research; Mar2026, Vol. 62 Issue 3, p1-15, 15p
Abstract: GaugeCam Remote Image Manager Educational 2 (GRIME2) is a free, open‐source Windows application for water level measurement in surface water bodies using ground‐based time‐lapse imagery. We evaluated a new "stop sign" (i.e., octagon shape) calibration target and GRIME2 algorithms by comparing results to other measurement methods over a 26‐month period. GRIME2 measurements were closely matched to visual observations of a staff gauge in images (Staff) and a traditional water‐level sensor (Transducer). GRIME2 and Transducer measurements were within ±0.1 ft (3.0 cm) of Staff measurements for 95% and 90% of paired measurements, respectively. After removing time periods when biofouling, ice and/or snow were visible on the GRIME2 target background, 98% of GRIME2 and Staff measurements were within 3 cm. Error metrics for all paired GRIME2 and Transducer measurements (70,668 pairs) included root mean square error (RMSE), absolute error (MAE), and Nash Sutcliffe Efficiency (NSE) of 3.6 cm, 2.3 cm and 0.83, respectively. With biofouling, ice and/or snow periods removed, error metrics improved to 2.1 cm, 1.5 cm, and 0.95, respectively, for 52,570 paired measurements, with 90% of paired measurements within 3 cm. The new GRIME2 greatly eases field setup and image processing. Only octagon facet length and a reference water level are needed to measure water level. Calibration is done on every image to account for camera movement, and the command line interface supports batch and automated processing for data dashboards. With proper calibration target placement and maintenance, GRIME2 can produce robust water level measurements over relatively long observation periods. Plain Language Summary: Water level is one of the most fundamental measurements for monitoring, using and managing water resources. Lake, stream and canal water levels are important for wildlife habitat, recreation, agricultural production and municipal and industrial water use. This study advances the use of trail (game) cameras for water level monitoring by integrating an octagon calibration target with open‐source GRIME2 software. This integrated system, including a specialized target background ("stop sign") installed in the water, enhances reliability and ease of use, delivering consistent and accurate measurements over many months. Maintenance issues, including cleaning the sign to remove biofouling, detecting the presence of ice or snow, and identifying when shadows or other lighting issues impact measurements, are key to successful monitoring. After accounting for these issues, 90% of GRIME2 measurements were within 3 cm (0.1 feet) of traditional pressure transducer measurements over a 26‐month period (52,570 images). Compared to visual measurements, GRIME2 measurements were within 3 cm 98% of the time. Importantly, the new system automatically adapts to inevitable shifts in the field of view (i.e., camera movement). Key Points: Monitoring water level with a camera is more feasible with smaller calibration target and software that accounts for field of view shiftsUnder optimal conditions, 90% of 52,570 paired measurements were within 0.1 ft (3.0 cm) of pressure transducer readingsMore than 95% of paired GRIME2 water‐level measurements were within 3 cm of visual readings of a staff gauge in images [ABSTRACT FROM AUTHOR]
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Database: Biomedical Index
Description
Abstract:GaugeCam Remote Image Manager Educational 2 (GRIME2) is a free, open‐source Windows application for water level measurement in surface water bodies using ground‐based time‐lapse imagery. We evaluated a new "stop sign" (i.e., octagon shape) calibration target and GRIME2 algorithms by comparing results to other measurement methods over a 26‐month period. GRIME2 measurements were closely matched to visual observations of a staff gauge in images (Staff) and a traditional water‐level sensor (Transducer). GRIME2 and Transducer measurements were within ±0.1 ft (3.0 cm) of Staff measurements for 95% and 90% of paired measurements, respectively. After removing time periods when biofouling, ice and/or snow were visible on the GRIME2 target background, 98% of GRIME2 and Staff measurements were within 3 cm. Error metrics for all paired GRIME2 and Transducer measurements (70,668 pairs) included root mean square error (RMSE), absolute error (MAE), and Nash Sutcliffe Efficiency (NSE) of 3.6 cm, 2.3 cm and 0.83, respectively. With biofouling, ice and/or snow periods removed, error metrics improved to 2.1 cm, 1.5 cm, and 0.95, respectively, for 52,570 paired measurements, with 90% of paired measurements within 3 cm. The new GRIME2 greatly eases field setup and image processing. Only octagon facet length and a reference water level are needed to measure water level. Calibration is done on every image to account for camera movement, and the command line interface supports batch and automated processing for data dashboards. With proper calibration target placement and maintenance, GRIME2 can produce robust water level measurements over relatively long observation periods. Plain Language Summary: Water level is one of the most fundamental measurements for monitoring, using and managing water resources. Lake, stream and canal water levels are important for wildlife habitat, recreation, agricultural production and municipal and industrial water use. This study advances the use of trail (game) cameras for water level monitoring by integrating an octagon calibration target with open‐source GRIME2 software. This integrated system, including a specialized target background ("stop sign") installed in the water, enhances reliability and ease of use, delivering consistent and accurate measurements over many months. Maintenance issues, including cleaning the sign to remove biofouling, detecting the presence of ice or snow, and identifying when shadows or other lighting issues impact measurements, are key to successful monitoring. After accounting for these issues, 90% of GRIME2 measurements were within 3 cm (0.1 feet) of traditional pressure transducer measurements over a 26‐month period (52,570 images). Compared to visual measurements, GRIME2 measurements were within 3 cm 98% of the time. Importantly, the new system automatically adapts to inevitable shifts in the field of view (i.e., camera movement). Key Points: Monitoring water level with a camera is more feasible with smaller calibration target and software that accounts for field of view shiftsUnder optimal conditions, 90% of 52,570 paired measurements were within 0.1 ft (3.0 cm) of pressure transducer readingsMore than 95% of paired GRIME2 water‐level measurements were within 3 cm of visual readings of a staff gauge in images [ABSTRACT FROM AUTHOR]
ISSN:00431397
DOI:10.1029/2025WR042244