A portable spectral detector for water quality assessment was developed, utilizing potassium nitrate and ammonium chloride standard solutions as the subjects of investigation. By preparing solutions with differing concentrations, spectral data ranging from 254 to 1275 nm was collected and subsequently preprocessed using methods such as multiple scattering correction (MSC), Savitzky–Golay filtering (SG), and standardization (SS). Estimation models were constructed employing modeling algorithms including Support Vector Machine-Multilayer Perceptron (SVM-MLP), Support Vector Regression (SVR), random forest (RF), RF-Lasso, and partial least squares regression (PLSR). The research revealed that the primary variation bands for NH₄⁺ and NO₃⁻ are concentrated within the 254–550 nm and 950–1275 nm ranges, respectively. For predicting ammonium chloride, the optimal model was found to be the SVM-MLP model, which utilized spectral data reduced to 400 feature bands after SS processing, achieving R² and RMSE of 0.8876 and 0.0883, respectively. For predicting potassium nitrate, the optimal model was the 1D Convolutional Neural Network (1DCNN) model applied to the full band of spectral data after SS processing, with R² and RMSE of 0.7758 and 0.1469, respectively. This study offers both theoretical and technical support for the practical implementation of spectral technology in rapid water quality monitoring.

Taking the Jurong Dongshan River as an illustrative case, we employed a Dajiang Phantom 4 RTK SE unmanned aerial vehicle (UAV) for single-lens tilt photography. Our investigation focused on examining the influence of varying flight altitudes (FA: 30 m, 60 m and 90 m) and the configuration of photo control points on two-dimentional (2D) or three-dimensional (3D) mapping accuracy of river embankments, slopes, and hydraulic structures, as well as the analysis of outcomes of 2D and 3D modeling under different FA conditions augmented with supplementary photographs. Our observations revealed that the longitude and elevation accuracy at 30 m FA were higher without photo control operations compared to those at 60 m and 90 m FA, and accuracy diminished as FA increased. Specifically, the longitude accuracy of the embankment photo control points exceeded that of the slope photo control points, whereas the elevation accuracy of the embankment photo control points was superior at FAs of 60 m and 90 m. The geographical location deviation of hydraulic structures (irrigation intake gates) in the 2D model was larger than that obtained in the 3D model. Notably, the incorporation of additional detailed photographs significantly augmented the modeling efficacy of UAV aerial survey data, especially in capturing intricate plant and slope details. It is recommended that the Phantom 4 RTK SE be used at FA of 90 m to establish a foundational channel model, along with capture of additional detailed photographs of crucial structures, slopes, etc., and obtaining geographic location information in 3D Models.