Channel Maps Research Articles

Channel Migration in Experimental River Networks Mapped by Particle Image Velocimetry

AbstractDeltaic river networks naturally reorganize as interconnected channels move to redistribute water, sediment, and nutrients across the delta plain. Network change is documented in decades of satellite imagery and laboratory experiments, but our ability to measure and understand channel movements is limited: existing methods are difficult to employ efficiently and struggle to distinguish between gradual movements (channel migration) and abrupt shifts in river course (channel avulsions). Here, we present a method to extract channel migration from plan‐view imagery using particle image velocimetry (PIV). Although originally designed to track particles moving in a fluid, PIV can be adapted to track channels moving on the delta surface, based on input estimates of channel width, migration timescale, and maps of the wet‐dry interface. Results for a delta experiment show that PIV‐derived vector fields accurately capture channel‐bank movements, as compared to manually drawn maps and an independent image‐registration technique. Unlike other methods, PIV targets the process of channel migration, excluding changes associated with channel avulsions and overbank flow. PIV‐derived migration rates from the experiment span an order of magnitude and are reduced under lower sediment supply and during sea‐level rise, supporting recent models. Together, results indicate that PIV offers a fast and reliable way to measure channel migration in river networks, that channel migration rates under non‐cohesive conditions can displace channels a distance comparable to their width in the time needed to aggrade ∼10% of the channel depth, and that migration direction is ∼60% orthogonal to mean flow direction and ∼40% flow‐parallel overall.

Epicardial and Endocardial Ablation Based on Channel Mapping in Patients With Ventricular Tachycardia and Chronic Chagasic Cardiomyopathy: Importance of Late Potential Mapping During Sinus Rhythm to Recognize the Critical Substrate.

BackgroundVentricular tachycardia (VT) in patients with chronic chagasic cardiomyopathy (CCC) is associated with considerable morbidity and mortality. Catheter ablation of VT in patients with CCC is very complex and challenging. The main goal of this work was to assess the efficacy of VT catheter ablation guided by late potentials (LPs) in patients with CCC.Methods and ResultsSeventeen consecutive patients with refractory VT and CCC were prospectively included in the study. Combined endo‐epicardial voltage and late activation mapping were obtained during baseline rhythm to define scarred and LP areas, respectively. The end point of the ablation procedure was the elimination of all identified LPs. Epicardial and endocardial dense scars (<0.5 mV) were detected in 17/17 and 15/17 patients, respectively. LPs were detected in the epicardial scars of 16/17 patients and in the endocardial scars of 14/15 patients. A total of 63 VTs were induced in 17 patients; 22/63 (33%) were stable and entrained, presenting LPs recorded in the isthmus sites. The end point of ablation was achieved in 15 of 17 patients. Ablation was not completed in 2 patients because of cardiac tamponade or vicinity of the phrenic nerve and circumflex artery. Three patients (2 with unsuccessful ablation) had VT recurrence during follow‐up (39 months).ConclusionsEndo‐epicardial LP mapping allows us to identify the putative isthmuses of different VTs and effectively perform catheter ablation in patients with CCC and drug‐refractory VTs.

Probing Gas Kinematics and PDR Structure around O-type Stars in the Sh 2-305 H ii Region

Abstract We report an observational study of the Galactic H ii region Sh 2-305/S305 using the [C ii] 158 μm line data, which are used to examine the gas dynamics and structure of photodissociation regions. The integrated [C ii] emission map at [39.4, 49.5] km s−1 spatially traces two shell-like structures (i.e., inner and outer neutral shells) having a total mass of ∼565 M ⊙. The inner neutral shell encompasses an O9.5V star at its center and has a compact ring-like appearance. However, the outer shell is seen with more extended and diffuse [C ii] emission, hosting an O8.5V star at its center, and surrounds the inner neutral shell. The velocity channel maps and position–velocity diagrams confirm the presence of a compact [C ii] shell embedded in the diffuse outer shell, and both the shells seem to expand with v exp ∼ 1.3 km s−1. The outer shell appears to be older than the inner shell, hinting that these shells are formed sequentially. The [C ii] profiles are examined toward S305, which are either double peaked or blue skewed and have the brighter redshifted component. The redshifted and blueshifted components spatially trace the inner and outer neutral shell geometry, respectively. The ionized, neutral, and molecular zones in S305 are seen adjacent to one another around the O-type stars. The regularly spaced dense molecular and dust clumps (mass ∼10–103 M ⊙) are investigated around the neutral shells, which might have originated as a result of gravitational instability in the shell of collected materials.

Protection switching schemes and mapping strategies for fail-operational hard real-time NoCs

Communication infrastructures designed for mixed-critical MPSoCs must provide isolation of traffic, hard real-time guarantees, and fault-tolerance. In previous work, we proposed the combination of protection-switching with a hybrid Time-Division-Multiplexed (TDM) and packet-switched Network-on-Chip (NoC) to achieve all three goals. In this paper, we present an FPGA implementation of such a NoC with all its features. We give synthesis results for the hybrid NoC, including the network interface, and show that our router uses over 32% fewer LUTs and registers than a competitive state-of-the-art router for mixed-critical MPSoC. We then explore different channel and task mapping strategies for critical applications which use protection switching and evaluate the effect these mappings have on the best-effort (BE) traffic in the system. Results show, that spreading out the critical traffic rather than naively dividing the system in critical and non-critical application domains is advantageous or even necessary in many cases and can allow for up to 13% more BE traffic. We give a comprehensive trade-off analysis of three protection switching schemes—1:n, 1:1, and 1+1—and show that 1+1 protection has less than half the worst case latency for critical traffic that 1:n and 1:1 protection have. At the same time, 1+1 protection, on average, only causes a 1.18% earlier saturation rate for BE traffic, which we consider to be affordable. We conclude that 1+1 protection is ideally suited for use in mixed-critical systems with high safety requirements.

Spatial Patterns and Sensitivity of Intermittent Stream Drying to Climate Variability

AbstractIntermittent streams comprise much of the global river network, and are expected to become more prevalent with climate change. Characterizing the expansion and contraction of intermittency in stream networks, and understanding how sensitive these dynamics are to climatic variability, is critical for predicting the trajectory of hydrologic regimes in a changing climate. Here, we consider the spatial patterns of stream intermittency, focusing on wetted channel conditions at the end of the dry season, and identify land cover, physiographic, and climate variables that influence surface water presence and variability across years. We trained statistical models with wetted channel mapping data from 25 streams over 7 years to predict both the spatial and interannual variability of the wetted channel network. We then used the models to assess intermittent stream dynamics across the Russian River watershed in northern California, USA. We found that an average of 3.7% of the stream network was reliably dry, while 16.1% was reliably wet at the end of the dry season, with the remainder of the network exhibiting variability in wetted conditions in response to antecedent precipitation. Both climatic and landscape characteristics controlled the extent of the wetted network, particularly antecedent precipitation at seasonal and annual time scales, highlighting the role of hydrologic memory in this system. Given predictions of increased climate volatility, an improved understanding of the spatial patterns and stability of dry season conditions in intermittent streams can inform climate risk assessments and strategies for protecting biodiversity and the ecosystem services that intermittent streams support.

Progressive kernel pruning with saliency mapping of input-output channels

As the smallest structural unit of feature mapping, the convolution kernel in a deep convolution neural networks (DCNN) convolutional layer is responsible for the input channel features to output channel features. A specific convolution kernel belongs to a specific group from the perspective of the input channel, and it belongs to a specific filter from the perspective of the output channel. If the input and output channels are simultaneously considered in the pruning process, the performance of the pruning model can be further improved. This paper proposes progressive kernel pruning with salient mapping of input-output channels, introduces the concept of input-output channel saliency and defines single-port salient mapping channels and dual-port salient mapping channels. This study demonstrates that single-port salient mapping channels can ensure that each input channel signal has a relatively strong convolution kernel mapped to the output channel, and vice versa. The dual-port salient mapping channel is a channel with high feature mapping abilities from both the input and output directions. Additionally, the average mapping ability measure index is defined, which is used to control the kernel pruning process of the single-port salient mapping channel to switch to the kernel pruning process of the dual-port salient mapping channel. The experimental results and analysis show that the method proposed in this paper can be used to effectively prune a heavyweight model and a lightweight model and can obtain a better accuracy under the conditions of higher compression ratio and acceleration ratios. For example, when VGG-16 is pruned on CIFAR-10, the compression ratio and acceleration ration are 91.00× and 15.24×, respectively, and the classification accuracy of the model decreased slightly by 0.22%. When ResNet-101 is pruned on ImageNet, the compression ratio and acceleration ratio are 3.90× and 3.38×, respectively, and the classification accuracy of the model decreased slightly by 0.48%. The proposed method is significantly better than state-of-the-art methods.

A Shallow–Deep Feature Fusion Method for Pedestrian Detection

In this paper, a shallow–deep feature fusion (SDFF) method is developed for pedestrian detection. Firstly, we propose a shallow feature-based method under the ACF framework of pedestrian detection. More precisely, improved Haar-like templates with Local FDA learning are used to filter the channel maps of ACF such that these Haar-like features are able to improve the discriminative power and therefore enhance the detection performance. The proposed shallow feature is also referred to as weighted subset-haar-like feature. It is efficient in pedestrian detection with a high recall rate and precise localization. Secondly, the proposed shallow feature-based detection method operates as a region proposal. A classifier equipped with ResNet is then used to refine the region proposals to judge whether each region contains a pedestrian or not. The extensive experiments evaluated on INRIA, Caltech, and TUD-Brussel datasets show that SDFF is an effective and efficient method for pedestrian detection.

Clipping inguinal lymphatics decreases lymphorrhoea after lymphadenectomy following cancer treatment: results from a randomized clinical trial

Background Post-operative lymphorrhea is a well-known complication of inguinal lymph node dissection. However, the interventions to reduce the duration of drain in situ have not been sufficiently elaborated. Objectives We evaluated the potential role of intra-operative mapping of lymphatic leakage with peri-incisional methylene blue injection and clipping of lymphatics after inguinal block dissection in reducing postoperative lymphorrhea. Methods We randomized 39 inguinal dissections done for various malignancies such as for carcinoma penis, urethra, malignant melanoma, rectum into 19 dissections (Interventional group) and 20 dissections (Control group). In the interventional group, after the completion of inguinal dissection, two ml of methylene blue dye was injected 4–8cm from the incision to identify the leaking lymphatics and they were clipped. Results The primary outcome was the decrease in duration of days of drain in situ and was found to have significant reduction of 3.07 days in the interventional arm. (p value-0.02). The secondary outcome was the reduction of 21 ml of mean drain output in the interventional group (p = 0.09). The number of lymphatics clipped was not found to have statistical correlation with the duration of drain in situ and the mean drain output. Conclusion The intraoperative mapping of lymphatic channels using methylene blue after inguinal dissection reduces the number of days of drain in situ.

Search for and Identification of Young Compact Galactic Supernova Remnants Using THOR

Young Supernova remnants (SNRs) with smaller angular sizes are likely missing from existing radio SNR catalogues, caused by observational constraints and selection effects. In order to find new compact radio SNR candidates, we searched the high angular resolution (25″) THOR radio survey of the first quadrant of the galaxy. We selected sources with non-thermal radio spectra. HI absorption spectra and channel maps were used to identify which sources are galactic and to estimate their distances. Two new compact SNRs were found: G31.299-0.493 and G18.760-0.072, of which the latter was a previously suggested SNR candidate. The distances to these SNRs are 5.0±0.3 kpc and 4.7±0.2 kpc, respectively. Based on the SN rate in the galaxy or on the statistics of known SNRs, we estimate that there are 15–20 not-yet detected compact SNRs in the galaxy and that the THOR survey area should contain three or four. Our detection of two SNRs (half the expected number) is consistent with the THOR sensitivity limit compared with the distribution of integrated flux densities of SNRs.

NOEMA Observations of CO Emission in Arp 142 and Arp 238

Abstract Previous studies have shown significant differences in the enhancement of the star formation rate (SFR) and star formation efficiency (SFE = SFR/M mol) between spiral–spiral and spiral–elliptical mergers. In order to shed light on the physical mechanism of these differences, we present NOEMA observations of the molecular gas distribution and kinematics (linear resolutions of ∼2 kpc) in two representative close major-merger star-forming pairs: the spiral–elliptical pair Arp 142 and the spiral–spiral pair Arp 238. The CO in Arp 142 is widely distributed over a highly distorted disk without any nuclear concentration, and an off-center ringlike structure is discovered in channel maps. The SFE varies significantly within Arp 142, with a starburst region (region 1) near the eastern tip of the distorted disk showing an SFE ∼ 0.3 dex above the mean of the control sample of isolated galaxies and the SFE of the main disk (region 4) 0.43 dex lower than the mean of the control sample. In contrast, the CO emission in Arp 238 is detected only in two compact sources at the galactic centers. Compared to the control sample, Arp 238-E shows an SFE enhancement of more than 1 dex, whereas Arp 238-W has an enhancement of ∼0.7 dex. We suggest that the extended CO distribution and large SFE variation in Arp 142 are due to an expanding large-scale ring triggered by a recent high-speed head-on collision between the spiral galaxy and the elliptical galaxy, and the compact CO sources with high SFEs in Arp 238 are associated with nuclear starbursts induced by gravitational tidal torques in a low-speed coplanar interaction.

Technology giants, educational policy and a preliminary mapping of networks and channels of influence in a Norwegian context

The article looks at the debate regarding the influence of the technology giants on educational policy. What strategies have existed on the part of the technology giants? Who have been the major actors within education? What kind of relations and networks have been established? The first part of the article focuses on relevant research internationally showing that the technology giants have taken the lead and that their objectives are to develop new long-term policy agendas. The development has been significantly intensified and to some extent changed during the pandemic. This has resulted in the emergence of new multisector coalitions and more complex networks which have potentially profound pedagogical implications. The second part accounts for a preliminary mapping of networks and channels of influence in a Norwegian context. Despite the differences between countries, political and educational systems, traditions and values, there are a number of the similarities in the field of educational technology. These include on a general level how the use of new technology is valued as a way of improving teaching and learning, but also how networks and relations are developed and function. The project that precedes the article is based on literature studies and inspired by network ethnographic approaches.

Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational Transitions

Abstract We studied the absorption features of CO lines against the continuum originating from the heated dust in the obscuring tori around active galactic nuclei (AGNs). We investigated the formation of absorption lines corresponding to the CO rotational transitions using three-dimensional non-LTE line transfer simulations considering the dust thermal emission. As in Papers I–III of this series, we performed post-processed radiative transfer calculations using the “radiation-driven fountain model” (Wada et al. 2016), which yields a geometrically thick obscuring structure around the nucleus. This model is consistent with the spectral energy distribution of the nearest type-2 Seyfert galaxy, the Circinus galaxy. We found that the continuum-subtracted channel maps of J = 4−3 and higher transitions show absorption regions along the disk midplane for an edge-on viewing angle. The spectra consist of multiple absorption and emission features, reflecting the internal inhomogeneous and turbulent structure of the torus. The deepest absorption feature is caused by the gas on the near side of the torus between r = 10 and 15 pc, which is located in front of the AGN-heated dust inside r ≃ 5 pc. We also found that a spatial resolution of 0.5–1.0 pc is necessary to resolve the absorption features. Moreover, the inclination angle must be close to the edge-on angle (i.e., ≳85°) to observe the absorption features. The findings of the present study imply that combining our radiation-hydrodynamic model with high-resolution observations of CO (7–6) by ALMA can provide new information about the internal structure of the molecular tori in nearby AGNs.

The analysis of water loses in the secondary channels of Bissua irrigation

This research aims to analyze the correlation between water efficiency, water losses, and channel density in the secondary channels of Bissua irrigation and figure them spatially. Channel was sampled purposively for different dense of a channel in the area based on irrigation channel map. The water inflow and outflow were measured in the selected segmented channels. Discharges, evaporation, and seepage data were used to determine water losses and their efficiencies. Spatial mapping was processed using ArcGIS 10.4 to figure the location of channels with their value of efficiencies and losses. The result shows that losses and efficiency range from 1.2 to 4.7 ×10-4 m3/s/m and 40 to 90%, respectively. The variation of channel density from 0.03 to 0.25 km/km2 found a negative exponential correlation between water efficiency, water losses, and channel density. In addition, water losses also have a positive correlation to the width of channels.

Single Image Defogging Algorithm Based on Sky Region Segmentation

The visibility, contrast and color fidelity of images acquired under foggy weather will decrease to a certain extent, image defogging is an important part of image processing. Since the dark channel prior is not applicable to the sky area, which results in the color distortion and some noise of the restored fog-free image. Based on the segmentation of the sky region, it is proposed to separately estimate the atmospheric light value and transmission map according to different regions, and finally generates a defogging image using the optimized synthetic global map. In order to divide the sky domain and the non-sky domain more accurately, the two results obtained by the threshold segmentation method for the dark channel map and the improved threshold segmentation method for the original foggy image are considered at the same time. In the step of estimating the transmittance of the sky domain, the dark channel map of sky domain is obtained based on HSI color space, making the sky area more natural after defogging. Experimental results show that the algorithm can achieve good defogging effect, smooth edge transition between regions, and the defogging images are more natural and clear.

Three‐dimensional feature maps and convolutional neural network‐based emotion recognition

In recent years, automatic emotion recognition renders human–computer interaction systems intelligent and friendly. Emotion recognition based on electroencephalogram (EEG) has received widespread attention and many research results have emerged, but how to establish an integrated temporal and spatial feature fusion and classification method with improved convolutional neural networks (CNNs) and how to utilize the spatial information of different electrode channels to improve the accuracy of emotion recognition in the deep learning are two important challenges. This paper proposes an emotion recognition method based on three-dimensional (3D) feature maps and CNNs. First, EEG data are calibrated with 3 s baseline data and divided into segments with 6 s time window, and then the wavelet energy ratio, wavelet entropy of five rhythms, and approximate entropy are extracted from each segment. Second, the extracted features are arranged according to EEG channel mapping positions, and then each segment is converted into a 3D feature map, which is used to simulate the relative position of electrode channels on the scalp and provides spatial information for emotion recognition. Finally, a CNN framework is designed to learn local connections among electrode channels from 3D feature maps and to improve the accuracy of emotion recognition. The experiments on data set for emotion analysis using physiological signals data set were conducted and the average classification accuracy of 93.61% and 94.04% for valence and arousal was attained in subject-dependent experiments while 83.83% and 84.53% in subject-independent experiments. The experimental results demonstrate that the proposed method has better classification accuracy than the state-of-the-art methods.

Single Image Haze Removal with Pixel-based Transmission Map Estimation

Adversary imaging condition such as in a hazy weather is a challenge in the community of image processing. To address the challenge of haze removal, several model-based approaches have been reported recently. Among them, a single image haze removal scheme based on dark channel prior (DCP) was presented in [1] and has been getting popular because of its satisfactory performance for most of cases. However, it is well-known that the DCP scheme is inherent of two fundamental problems: high computational cost and over-exposure. In this paper, the objective of proposed dehazing algorithm (PDA) is to deal with the two problems in [1], where atmospheric light is estimated from the dark channel and pixel-based transmission map estimation is employed. Examples are given to verify the PDA where comparison with the DCP scheme and other well-known schemes are made as well. The simulation results indicate that the PDA has similar or better dehazing performance than the compared schemes in the given examples, when both mood retention and visibility improvement are considered.

COVID-19 Detection from X-ray Images using Multi-Kernel-Size Spatial-Channel Attention Network

Novel coronavirus 2019 (COVID-19) has spread rapidly around the world and is threatening the health and lives of people worldwide. Early detection of COVID-19 positive patients and timely isolation of the patients are essential to prevent its spread. Chest X-ray images of COVID-19 patients often show the characteristics of multifocality, bilateral hairy glass turbidity, patchy network turbidity, etc. It is crucial to design a method to automatically identify COVID-19 from chest X-ray images to help diagnosis and prognosis. Existing studies for the classification of COVID-19 rarely consider the role of attention mechanisms on the classification of chest X-ray images and fail to capture the cross-channel and cross-spatial interrelationships in multiple scopes. This paper proposes a multi-kernel-size spatial-channel attention method to detect COVID-19 from chest X-ray images. Our proposed method consists of three stages. The first stage is feature extraction. The second stage contains two parallel multi-kernel-size attention modules: multi-kernel-size spatial attention and multi-kernel-size channel attention. The two modules capture the cross-channel and cross-spatial interrelationships in multiple scopes using multiple 1D and 2D convolutional kernels of different sizes to obtain channel and spatial attention feature maps. The third stage is the classification module. We integrate the chest X-ray images from three public datasets: COVID-19 Chest X-ray Dataset Initiative, ActualMed COVID-19 Chest X-ray Dataset Initiative, and COVID-19 radiography database for evaluation. Experimental results demonstrate that the proposed method improves the performance of COVID-19 detection and achieves an accuracy of 98.2%.

Spiral Arms and a Massive Dust Disk with Non-Keplerian Kinematics: Possible Evidence for Gravitational Instability in the Disk of Elias 2–27

Abstract To determine the origin of the spiral structure observed in the dust continuum emission of Elias 2–27 we analyze multiwavelength continuum ALMA data with a resolution of ∼0.″2 (∼23 au) at 0.89, 1.3, and 3.3 mm. We also study the kinematics of the disk with 13CO and C18O ALMA observations in the J = 3–2 transition. The spiral arm morphology is recovered at all wavelengths in the dust continuum observations, where we measure contrast and spectral index variations along the spiral arms and detect subtle dust-trapping signatures. We determine that the emission from the midplane is cold and interpret the optical depth results as signatures of a disk mass higher than previous constraints. From the gas data, we search for deviations from Keplerian motion and trace the morphology of the emitting surfaces and the velocity profiles. We find an azimuthally varying emission layer height in the system, large-scale emission surrounding the disk, and strong perturbations in the channel maps, colocated with the spirals. Additionally, we develop multigrain dust and gas hydrodynamical simulations of a gravitationally unstable disk and compare them to the observations. Given the large-scale emission and highly perturbed gas structure, together with the comparison of continuum observations to theoretical predictions, we propose infall-triggered gravitational instabilities as the origin for the observed spiral structure.

The intensity of slope and fluvial processes after a catastrophic windthrow event in small catchments in the Tatra Mountains

Strong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

The Disc Miner

Context. The study of disc kinematics has recently opened up as a promising method to detect unseen planets. However, a systematic, statistically meaningful analysis of such an approach remains missing in the field. Aims. The aim of this work is to devise an automated, statistically robust technique to identify and quantify kinematical perturbations induced by the presence of planets in a gas disc, and to accurately infer the location of the planets. Methods. We produced hydrodynamical simulations of planet–disc interactions with different planet masses, namely 0.3, 1.0, and 3.0 MJup, at a radius of Rp = 100 au in the disc, and performed radiative transfer calculations of CO to simulate observables for a disc inclination of − 45°, and for 13 planet azimuths. We then fitted the synthetic data cubes with a Keplerian model of the channel-by-channel emission using the DISCMINER package. Lastly, we compared the synthetic cubes with the best-fit model to: extract deviations from Keplerian rotation; and quantify both large-scale and localised intensity, line width, and velocity fluctuations triggered by the embedded planets and provide strong constraints on their location in the disc. We assess the statistical significance of the detections using the peak and variance of the planet-driven velocity fluctuations. Results. Our findings suggest that a careful inspection of line intensity profiles to analyse gas kinematics in discs is a robust method to reveal embedded, otherwise unseen planets, as well as the location of gas gaps. We claim that a simultaneous study of line-of-sight velocities and intensities is crucial to understanding the origin of the observed velocity perturbations. In particular, the combined contribution of the upper and lower emitting surfaces of the disc plays a central role in setting the observed gas velocities. This joint effect is especially prominent and hard to predict at the location of a gap or cavity, which can lead to artificial deviations from Keplerian rotation depending on how the disc velocities are retrieved. Furthermore, regardless of their origin, gas gaps alone are capable of producing kink-like features on intensity channel maps, which are often attributed to the presence of planets. Our technique, based on line centroid differences, takes all this into account to capture only the strongest, localised, planet-driven perturbations. It does not get confused by axisymmetric velocity perturbations that may result from non-planetary mechanisms. The method can detect all three simulated planets, at all azimuths, with an average accuracy of ±3° in azimuth and ±8 au in radius. As expected, velocity fluctuations driven by planets increase in magnitude as a function of the planet mass. Furthermore, owing to disc structure and line-of-sight projection effects, planets at azimuths close to ±45° yield the highest velocity fluctuations, whereas those at limiting cases, 0° and ±90°, drive the lowest. The observed peak velocities typically range within 40−70, 70−170, and 130−450 m s−1 for 0.3, 1.0, and 3.0 MJup planets, respectively. Our analysis indicates that the variance of peak velocities is boosted near planets because of organised gas motions prompted by the localised gravitational well of planets. We propose an approach that exploits this velocity coherence to provide, for the first time, statistically significant detections of localised planet-driven perturbations in the gas disc kinematics.