Depth Scanning Research Articles

Critical matters in using Attenuated Total Reflectance Fourier Transform Infrared to characterize the polymer degradation in Styrene–Butadiene–Styrene-modified asphalt binders

Styrene–Butadiene–Styrene (SBS) polymer is widely employed as an outstanding asphalt modifier. However, inevitable field aging will cause degradation of SBS polymer and consequently shortened pavement lifespan. To characterize the SBS degradation of SBS-modified asphalt (SBSMA), infrared spectroscopy is frequently utilized and the infrared intensity of 966 cm−1 peak is usually employed as an SBS content indicator. However, in this study, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), which is a promising alternative to conventional transmission-FTIR, yielded an abnormal 966 cm−1 peak intensity growth after asphalt aging. To investigate this phenomenon, two types of SBSMAs (radial and linear) were laboratorial aged and their infrared spectra obtained by ART-FTIR and transmission-FTIR were compared. It was found that aging significantly reduced the SBS polymer particle size and facilitated SBS dispersion, and a more uniform SBS dispersion combined with the relatively shallow scanning depth of ATR-FTIR (2 μm) caused the different result between ATR-FTIR and transmission-FTIR. A mathematical model was presented to explain this phenomenon. Moreover, a novel infrared index specially developed for ATR-FTIR was proposed to assess the degradation of SBS polymer.

Long scan depth optical coherence tomography on imaging accommodation: impact of enhanced axial resolution, signal-to-noise ratio and speed

BackgroundSpectral domain optical coherence tomography (SD-OCT) was a useful tool to study accommodation in human eye, but the maximum image depth is limited due to the decreased signal-to-noise ratio (SNR). In this study, improving optical resolutions, speeds and the SNR were achieved by custom built SD-OCT, and the evaluation of the impact of the improvement during accommodation was investigated.MethodsThree systems with different spectrometer designs, including two Charge Coupled Device (CCD) cameras and one Complementary Metal-Oxide-Semiconductor Transistor (CMOS) camera, were tested. We measured the point spread functions of a mirror at different positions to obtain the axial resolution and the SNR of three OCT systems powered with a light source with a 50 nm bandwidth, centered at a wavelength of 840 nm. Two normal subjects, aged 26 and 47, respectively, and one 75-year-old patient with an intraocular lens implanted were imaged.ResultsThe results indicated that spectrometers using cameras with 4096 camera pixels optimized the axial resolutions, due to the use of the full spectrum provided by the light source. The CCD camera system with 4096 pixels had the highest SNR and the best image quality. The system with the CMOS camera with 4096 pixels had the highest speed but had a compromised SNR compared to the CCD camera with 4096 pixels.ConclusionsUsing these three OCT systems, we imaged the anterior segment of the human eye before and after accommodation, which showed similar results among the different systems. The system using the CMOS camera with an ultra-long scan depth, high resolution and high scan speed exhibited the best overall performance and therefore was recommended for imaging real-time accommodation.

Experimental investigation of subsurface damage depth of lapped optics by fluorescent method

Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths.

3D imaging scanner.

This paper proposes a multi-view three-dimensional display method based on a scanning imaging system with the light-intensity characteristic recorded by an improved flatbed scanner. Within the effective scanning depth of the imaging sensor, two transmission images are each simultaneously acquired by two linear CCD modules with different focal planes. Then the phase gradient information of the target can be obtained by an appropriate retrieval algorithm. Further, the multi-view three-dimensional effect is presented through dynamic angles of view. Theoretical analysis of this method is discussed, and experiments are carried out by building a scanner. The experiment results are presented with an algae specimen and transparent beads. We hope this method can be applied to present the three-dimensional effect of objects of flat translucent multilayer structure with a wide field of view.

Graphene oxide and TiO2 based PMMA nanocomposites for dental applications: A comprehensive study of the mechanical properties

This work reports synthesis of PMMA/TiO2 blend nanocomposite for its application as dental materials. Two different amount of TiO2nano particles 1% (wt.) was mixed homogeneously through melt compounding with constant ratio of PMMA to obtain desired properties. The properties of these two bend nanocomposites were compared GO (0.001% wt.) reinforcedPMMAnanocomposite for the same purpose. Asprepared blend nanocomposites were characterized by Field Emission Scanning Electron Microscopy (FESEM), depth indentation, and sratch analysis. Moreover, this work also showing effect of different amount of TiO2 on open ring hole structures and matrix droplet morphology. So, that this work may open up an opportunities to produce new compatibilized blend that are of great interest in the industrial applications using specific amount of TiO2.

Optic disc vessel density in nonglaucomatous and glaucomatous eyes: an enhanced-depth imaging optical coherence tomography angiography study.

PurposeTo evaluate the ability of enhanced-depth imaging (EDI) optical coherence tomography angiography (OCTA) to detect vascular signals inside the glaucomatous optic disc.Patients and methodsTen glaucomatous eyes of 8 subjects and 11 nonglaucomatous eyes of 7 subjects underwent EDI and conventional OCTA for optic disc analysis. The optic disc vessel density (VD) at maximum scan depth (2 mm) was compared between the 2 methods and between glaucomatous and nonglaucomatous eyes. Regression analysis was used to determine the factors affecting disc VD.ResultsThe median (25th, 75th percentile) of the visual field mean deviation was −20.5 (−25.1, −13.5) dB in glaucoma. The disc VD measured with the EDI method was significantly greater than that measured with the conventional method in glaucoma and nonglaucoma. The disc VD was also significantly lower in glaucoma than in nonglaucoma. The disc VD and mean deviation were significantly and positively correlated in both methods (conventional: R2=0.27, EDI: R2=0.22).ConclusionThe correlation between disc VD and glaucoma severity was comparable between conventional and EDI measurements. Images obtained with EDI-OCTA have the additional benefit of revealing more vascular signals in deeper layers. The disc VD, as determined by both conventional and EDI-OCTA methods, may be an indicator of glaucoma severity.

Chemical and valence reconstruction at the surface ofSmB6revealed by means of resonant soft x-ray reflectometry

Samarium hexaboride (SmB$_6$), a Kondo insulator with mixed valence, has recently attracted much attention as a possible host for correlated topological surface states. Here, we use a combination of x-ray absorption and reflectometry techniques, backed up with a theoretical model for the resonant $M_{4,5}$ absorption edge of Sm and photoemission data, to establish laterally averaged chemical and valence depth profiles at the surface of SmB$_6$. We show that upon cleaving, the highly polar (001) surface of SmB$_6$ undergoes substantial chemical and valence reconstruction, resulting in boron termination and a Sm$^{3+}$ dominated sub-surface region. Whereas at room temperature, the reconstruction occurs on a time scale of less than two hours, it takes about 24 hours below 50 K. The boron termination is eventually established, irrespective of the initial termination. Our findings reconcile earlier depth resolved photoemission and scanning tunneling spectroscopy studies performed at different temperatures and are important for better control of polarity and, as a consequence, surface states in this system.

F32. Very-high vs high resolution sonography in the evaluation of the posterior tibial and sural nerve: Preliminary data in healthy subjects

High resolution ultrasonography (HRUS) of peripheral nerves is an emerging tool in investigating peripheral nerves, complementary to electrodiagnostic tests, and it is commonly performed using a linear array transducer with upper frequencies between 12 and 19 MHz. Since 2016 a very-high-resolution US (VHRUS) device is available for clinical use (Vevo-MD) that incorporates transducers with upper frequencies of 48 MHz (pixel resolution 50 μm, depth 2.3 cm) and 70 MHz (pixel resolution 30 μm, depth 1 cm). Our aim was to investigate the potential role of VHRUS in the assessment of the posterior tibial nerve (PTN) and sural nerve (SN) healthy echographic features being both commonly involved in peripheral neuropathies. We studied these nerves (at the ankle) in 10 healthy subjects, comparing images obtained with VHRUS to those usually obtained with a 19 MHz HRUS. In particular, we compared 19 vs 48 MHz for PNT and 19 vs 70 MHz for SN. We measured nerves’ areas, perimeters and fascicular pattern obtained from the images acquired with both devices by using dedicated offline post-processing tools, and we compared the respective values. Our data show significant agreement in the measurements of area and perimeter obtained with both devices. However, using VHRUS we experienced a much higher degree of confidence in visualizing both nerves and their internal structure thanks to its superior spatial resolution. We also noticed that scanning depth was always sufficient for this diagnostic task. VHRUS shows promising advantages compared with HRUS although further studies are needed to validate its use also in subjects with well-established peripheral neuropathies.

Ultrawide-Field OCT to Investigate Relationships between Myopic Macular Retinoschisis and Posterior Staphyloma

To investigate the relationships between myopic macular retinoschisis (MRS) and posterior staphylomas and to reveal the characteristics of other retinal lesions associated with MRS. Retrospective, observational case series. Seven hundred twenty-nine eyes of 420 patients with high myopia, which was defined as myopic refractive error of more than -8.0 diopters or an axial length longer than 26.5 mm. Highly myopic eyes were examined by ultrawide-field (UWF) swept-source (SS) OCT with scan width of up to 23 mm and scan depth of 5 mm. The OCT features of MRS and posterior staphylomas and their spatial relationship were examined in UWF SS OCT images. Associations between MRS and staphylomas. In 729 eyes with mean axial length of 30.2±2.1 mm, posterior staphyloma was detected in 482 eyes (66.1%) and MRS was detected in 136 eyes (18.7%). All 136 eyes with an MRS showed outer retinoschisis, and 40 eyes (29.4%) also showed inner retinoschisis. Posterior staphyloma was detected significantly more frequently in eyes with MRS (117/136 [86.0%]) than in eyes without MRS (365/593 [61.6%]; P < 0.001). In all eyes with both staphyloma and outer retinoschisis, the area of the outer retinoschisis was restricted to the area within the staphyloma. In 1 of the 19 eyes with outer retinoschisis but without staphyloma, the outer retinoschisis extended beyond the range of the scanned fundus area. Among the 40 eyes with inner retinoschisis, the inner retinoschisis was located within the region of the outer retinoschisis in 39 eyes (97.5%). In all eyes with inner retinoschisis, retinal lesions causing an inward-directed tractional force were found within the area of the inner retinoschisis. In highly myopic eyes, the sites of the MRS and staphylomas were spatially related to each other. Posterior-directed force in association with staphylomas, and an inward-directed force resulting from epiretinal membranes or vitreoretinal attachments, may act as causative factors for MRS. However, the exact mechanisms related to the development of an MRS are probably diverse and complex.

3D Reconstruction of Scoliotic Spines from Stereoradiography and Depth Imaging.

Spine shape can be reconstructed from stereoradiography, but often requires specialized infrastructure or fails to account for subject posture. In this paper a protocol is presented for stereo reconstructions that integrates surface recordings with radiography and naturally accounts for variations in patient posture. Low cost depth cameras are added to an existing radiographic system to capture patient pose. A statistical model of human body shape is learned from public datasets and registered to depth scans, providing 3D correspondence across images for stereo reconstruction of radiographic landmarks. A radiographic phantom was used to validate these methods in vitro with RMS 3D landmark reconstruction error of 2.0mm. Surfaces were automatically and reliably registered, with SD 12mm translation disparity and SD .5° rotation. The proposed method is suitable for 3D radiographic reconstructions and may be beneficial in compensating for involuntary patient motion.

KTN-based high-speed axial and lateral scanning technique for an optical coherence tomography system and application to dental imaging.

A high-speed 840nm based polarization-sensitive time domain optical coherence tomography (PSOCT) technique is proposed and demonstrated based on the quadratic electro-optic property of potassium tantalate niobate (KTN) crystals. A longitudinal (axial) scanning depth of ≈10 μm is obtained for an applied AC voltage of 600V, at 1000Hz and temperature maintained around 40°C. The OCT system with the KTN-based electro-optic delay line combined with a linear actuation is extended to image an early dental demineralization. For enhanced contrast by the elimination of the strong surface reflection from the sample and high-speed imaging, the quadratic electro-optically tunable PSOCT technique is proposed and demonstrated. Further, a lateral scanning range of 490μm is also demonstrated by controlling the KTN temperature at 35°C for an applied voltage of 600V on the tooth sample. This KTN-based quadratic electro-optic delay line combined with lateral scan approach provides an automated high-speed two-dimensional scanning of samples of interest.

Rapid and Nondestructive Detection of Pesticide Residues by Depth-Profiling Fourier Transform Infrared Photoacoustic Spectroscopy.

Detection of pesticide residues is important for ensuring food safety, and it has assumed increased significance. Traditional analytical methods are known for being destructive and cost- and time-intensive. In this study, depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was successfully used as an in situ, nondestructive, and rapid method for detecting tricyclazole residues on three metal surfaces (copper, aluminum, and iron) and subsequently, on the surfaces of fresh rice leaves and ripe husks. Four moving mirror velocities, that is, 0.32, 0.63, 0.95, and 1.90 cm s–1 were used for recording the spectra. The results indicated that the moving mirror velocity of 0.95 cm s–1 was optimal for depth profiling, and the obtained spectra showed a strong absorption band at around 1200 cm–1, corresponding to the C–N bond in tricyclazole. This band could be used for monitoring tricyclazole residues on plant surfaces. Principal component analysis confirmed the detection of tricyclazole on the basis of its spectral information. Considering the scanning depth and the thickness of the plant cuticle, FTIR-PAS can be an effective means for detecting and monitoring similar organonitrogen pesticide residues.

Multimodal Hierarchical Face Recognition using Information from 2.5D Images

Facial recognition under uncontrolled acquisition environments faces major challenges that limit the deployment of real-life systems. The use of 2.5D information can be used to improve discriminative power of such systems in conditions where RGB information alone would fail. In this paper we propose a multimodal extension of a previous work, based on SIFT descriptors of RGB images, integrated with LBP information obtained from depth scans, modeled by an hierarchical framework motivated by principles of human cognition. The framework was tested on EURECOM dataset and proved that the inclusion of depth information improved significantly the results in all the tested conditions, compared to independent unimodal approaches.

Submicron probes for scanning electrochemical microscopy

To improve the spatial resolutions of scanning electrochemical microscopy (SECM) imaging, the laser-pulled submicron electrode fabrication method was explored in this work. Manual polishing of a laser-pulled Pt nanoelectrode exposed a Pt tip diameter of 250 nm with a ratio of the tip glass to exposed Pt disc (RG) of 30. This fabricated submicron probe was then utilized to study the electrochemical functionality of an independently addressable microband electrodes (IAME) sample using SECM. In the constant imaging mode of SECM, where the probe is scanned linearly across the sample at a fixed z position, SECM demonstrated higher resolution than that of the conventional micrometer electrodes when the feedback currents from the Pt and glass microbands were characterized. In addition, the depth scan imaging mode of SECM was also used to extract experimental horizontal line scans and probe approach curves for analysis. Three-dimensional (3D) simulations of the IAME–SECM probe experiments were explored for the first time to quantify the tip-to-sample distances, tilt angle of the sample (or electrode), and height of the Pt microbands. The experimentally characterized height was found to be similar to manufacturer specification (125 nm vs 110 nm). Furthermore, the more computationally demanding 3D simulation of the true IAME sample geometry (110 nm height of the Pt microbands) revealed minimal difference in feedback behaviours in comparison with the idealized flat geometry. The removal of this simulation complexity was proved to be sufficient for SECM analysis of the IAME sample by a 250 nm Pt probe, which greatly saves computation resources.

The effects of long duration chronic exposure to hexavalent chromium on single live cells interrogated by scanning electrochemical microscopy

Chromium is a useful heavy metal which has been employed in numerous industry and house applications. However, there are several known health risks associated with its uses. Cr (VI) is a toxic heavy metal format which serves no essential biological role in humans. It has been associated with oxidative stress, cytotoxicity, and carcinogenicity. Contamination of groundwater or soil due to improper handling lead to long term environmental damage. This study explores the effects of long duration chronic exposure to Cr (VI) on live human cells. Herein, scanning electrochemical microscopy (SECM) depth scan imaging was employed to monitor the membrane permeability of single live human bladder cancer (T24) cells following incubation with various Cr (VI) concentration stimuli. SECM was used to provide insights into the long duration effects on membrane homeostasis of individual cells exposed to constant levels of Cr (VI). Further investigation of total population viability was performed by MTT assay. Dependent on the exposure time, transition between three distinct trends was observed. At short incubation times (≤1–3 h) with low concentrations of Cr (VI) (0–10 μM), membrane permeability was largely unaffected. As time increased a decrease in membrane permeability coefficient was observed, reaching a minimum at 3–6 h. Following this a dramatic increase in membrane permeability was observed as cell viability decreased. Higher concentrations were also found to accelerate the timeframe at which these trends occurred. These findings further demonstrate the strength of SECM as a bioanalytical technique for monitoring cellular homeostasis.

Axial elongation measured by long scan depth optical coherence tomography during pilocarpine-induced accommodation in intraocular lens-implanted eyes

We used an ultra-long scan depth optical coherence tomography (UL-OCT) system to investigate changes in axial biometry of pseudophakic eyes during pilocarpine- induced accommodation. The right eyes from 25 healthy subjects (age range 49 to 84 years) with an intraocular lens (IOL) were imaged twice in the non-accommodative and the accommodative states. A custom-built UL-OCT instrument imaged the whole eye. Then accommodation was induced by two drops of 0.5% pilocarpine hydrochloride separated by a 5-minute interval. Following the same protocol, images were acquired again 30 minutes after the first drop. The central corneal thickness (CCT), anterior chamber depth (ACD), IOL thickness (IOLT), and vitreous length (VL) were obtained using custom automated software. The axial length (AL) was calculated by summing the CCT, ACD, IOLT, and VL. With accommodation, ACD increased by +0.08 ± 0.09 mm, while the VL decreased by −0.04 ± 0.09 mm (paired t-test each, P<0.05). CCT and IOLT remained constant during accommodation (P > 0.05). The non-accommodative AL was 23.47 ± 0.93 mm, and it increased by +0.04 ± 0.04 mm after accommodation (P<0.01). The AL increased and the IOL moved backward during pilocarpine-induced accommodation in pseudophakic eyes.

Energy level determination in bulk heterojunction systems using photoemission yield spectroscopy: case of P3HT:PCBM

Ultraviolet photoelectron spectroscopy (UPS) is commonly used method for energy level determination using planar heterojunction samples in either metal/organic or organic/organic systems. Only some attempts have been made in the study of bulk heterojunction systems. Photoemission yield spectroscopy (PYS) could be applied as a method for organic compound–organic compound interface studies in bulk heterojunction samples. Contrary to the UPS, PYS method does not require ultra-high vacuum, which simplifies experiment setup. Also, scanning depth of PYS is in the range of tens of nanometers, which allows studying deeper layers of the sample instead of only surface layer. In this work, poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk heterojunction thin films were studied as a model system. A mass ratio between P3HT and PCBM in the system was varied from 1:0 to 1:50. Ionization energy dependence on this ratio was studied using two methods: UPS and PYS. To study the influence of the sample morphology on the PYS measurements and obtainable results, phase-separated and homogeneously distributed samples were prepared for analyses. P3HT ionization energy shift of 0.40 eV was observed in the samples made from chloroform solution. Experiments showed the need for a low degree of phase separation between P3HT and PCBM to observe P3HT ionization energy shift using PYS. On the contrary, no ionization energy shift of P3HT was observed in the UPS measurements for the same systems.

Penetration of fluorescent silica nanoparticles into the cornea

Nanoparticles-based drug/gene delivery is being investigated for therapeutic management of various ocular disorders. In this study, we have examined the penetration of monodispersed silica nanoparticles (NPs), which were stained with Rhodamine B (RhB) or labelled with fluorescein isothiocyanate (FITC), across freshly isolated porcine cornea at a microscopic level using a custom-built confocal scanning microfluorometer (CSMF).CSMF had been developed previously for quantitative measurements of trans-corneal fluorescence. With a 40x objective (water immersion, 1.2 mm working distance; Zeiss), CSMF enables a depth resolution of ∼ 7 µm in trans-corneal fluorescence measurements with a signal/noise ratio > 50. The excitation in the CSMF is in the form of a slit beam, which is obtained by filtering the output of a white LED (10 W; modulated as a sine wave at 10 kHz) through an interference filter (470 ± 10 nm). The emission, collected through exit slit held in the eyepiece (referred to as the collection slit), is passed through a barrier filter with a cutoff at 510 nm. The collection and excitation slits are held confocal to each other so that depth-resolved measurements are obtained during depth scanning. The emission, as well as scattered light are detected by photomultiplier tubes and amplified using a lock-in amplifier. The sync signal of the function generator employed for modulation of the LED was coupled to the reference input of the lock-in amplifier.Penetration of the RhB-stained or FITC-labelled NPs were characterized with excised porcine eyes mounted underneath the objective of the microscope on a nanostage. Topical administration of RhB in solution partitioned readily into the corneal epithelium and distributed into the stroma as observed by an increase in RhB fluorescence over time. Administration of RhB-stained silica NPs also led to an increase in fluorescence emission, but it was largely from the epithelium and weakly from the anterior stroma. On the other hand, topical FITC-labelled NPs produced an increase in fluorescence only from the epithelium but not from the stroma. When RhB-stained or FITC-labelled silica NPs were administered on the bare stroma, a significant fluorescence was observed even from deeper layers of the tissue.Based on our observations, we conclude that while silica NPs are transported across the epithelium possibly by iterative endocytosis and exocytosis, their penetration into the corneal stroma is negligible at 24 hrs. The RhB fluorescence from the anterior stroma following topical RhB-stained NPs suggests a slow release of the dye from the NPs and its subsequent penetration into the stroma. Furthermore, a pronounced penetration of NPs into the stroma following their administration on the bare stroma is possibly accelerated by a convective mechanism secondary to imbibition pressure that exists in the corneal stroma

Axial scanning with pulse shaping in temporal focusing two-photon microscopy for fast three-dimensional imaging

By integrating ultrafast laser pulse shaping into temporal focusing two-photon microscopy, a high-speed 3D imaging method is developed. This 3D imaging system requires neither laser beam steering nor sample mechanical scanning. The z scanning is achieved by shifting the temporal focal plane via applying different group velocity dispersions on the femtosecond laser spectrum in the temporal focusing two-photon microscope, and this group velocity dispersion control is done with the pulse shaping method by applying modulation functions on an acoustic optic modulator which diffracts the laser spectrum. The dependence of scanning depth on the applied electronic signals which can be tuned at kHz speed was characterized. Its high-speed 3D imaging capability was demonstrated by imaging fluorescence microspheres in a volume of 100 × 100 × 80 µm3.

Multitemporal Accuracy and Precision Assessment of Unmanned Aerial System Photogrammetry for Slope-Scale Snow Depth Maps in Alpine Terrain

Reliable and timely information on the spatio-temporal distribution of snow in alpine terrain plays an important role for a wide range of applications. Unmanned aerial system (UAS) photogrammetry is increasingly applied to cost-efficiently map the snow depth at very high resolution with flexible applicability. However, crucial questions regarding quality and repeatability of this technique are still under discussion. Here we present a multitemporal accuracy and precision assessment of UAS photogrammetry for snow depth mapping on the slope-scale. We mapped a 0.12 km2 large snow-covered study site, located in a high-alpine valley in Western Austria. 12 UAS flights were performed to acquire imagery at 0.05 m ground sampling distance in visible (VIS) and near-infrared (NIR) wavelengths with a modified commercial, off-the-shelf sensor mounted on a custom-built fixed-wing UAS. The imagery was processed with structure-from-motion photogrammetry software to generate orthophotos, digital surface models (DSMs) and snow depth maps (SDMs). Accuracy of DSMs and SDMs were assessed with terrestrial laser scanning and manual snow depth probing, respectively. The results show that under good illumination conditions (study site in full sunlight), the DSMs and SDMs were acquired with an accuracy of ≤ 0.25 and ≤ 0.29 m (both at 1σ), respectively. In case of poorly illuminated snow surfaces (study site shadowed), the NIR imagery provided higher accuracy (0.19 m; 0.23 m) than VIS imagery (0.49 m; 0.37 m). The precision of the UASSDMs was 0.04 m for a small, stable area and below 0.33 m for the whole study site (both at 1σ).