Long-term Monitoring Purposes Research Articles

A feasibility study on time-lapse transient electromagnetics for monitoring groundwater dynamics

Time-lapse geophysical studies have been used as noninvasive tools to study subsurface processes. However, compared to direct current resistivity methods, the transient electromagnetic (TEM) method has not been explored in much detail for time-lapse investigations. Here, we introduce the use of a monitoring TEM (mTEM) system and methodology for long-term groundwater monitoring purposes. The system can run measurements automatically and the modeling approach uses a time-constrained inversion (TCI) scheme based on an existing laterally constrained inversion scheme. Instead of lateral constraints that traditionally ensure lateral coherency between measurements, temporal constraints are used to control the temporal coherency between measurements. Synthetic analysis demonstrates that very tight time constraints on resistivities and a time constraint on the depth to the water table fixed at a fraction of the expected annual water table variation is needed to track water table changes at the decimeter level. Furthermore, the synthetic analysis indicates that the mTEM method can track annual variations in the water table with amplitudes as low as 0.6 m with a mean absolute error of 0.2 at depths between 16 m and 30 m. A field example consisting of 233 1D TEM measurements acquired over 10 months using the mTEM instrument supports the synthetic results. The estimated water table depth from the TCI scheme reproduces the variation in the water table accurately, as confirmed by measurements from a water level data logger in a nearby well. The differences between the results from the TEM monitoring system and the diver measurements are in the range of ±0.1 m with an average absolute difference of 0.05 m. This study demonstrates the potential to monitor changes in the groundwater level noninvasively.

Inherently Charged Particle (ICP) Sensor Design

Ambient particles from natural and anthropogenic sources are a major cause of premature deaths globally. While there are many instruments suitable for scientific measurements of aerosols, better methods for long-term monitoring purposes are still needed, especially low-maintenance, affordable solutions for ultrafine particles. In this article, we present a new sensor design and prototype, the inherently charged particle (ICP) sensor, which uses the preexisting electrical charge of particles to measure particle concentration, instead of employing a charging mechanism, as is typical for instruments based on electrical detection. When the ICP-sensor is employed in conjunction with another instrument, information on the particle charge state can also be derived. We present the results of a laboratory characterization as well as two measurements in suggested applications: 1) engine exhaust measurements and 2) ambient measurements in a traffic environment, where we compare the sensor response to three particle concentration metrics: 1) number; 2) surface area; and 3) mass. The sensor proved suitable for both applications, the signal correlated best with number concentration in the engine emission measurements and with particle surface area in the ambient measurements. The measured charge concentrations were well-correlated ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{\,2} &gt;0.8$ </tex-math></inline-formula> ) with theoretical values calculated from the number size distribution assuming an equilibrium charge distribution.

Research on Production Profiling Interpretation Technology Based on Microbial DNA Sequencing Diagnostics of Unconventional Reservoirs

Production profiling technology is an important method for monitoring the dynamics of oil and gas reservoirs which can effectively improve the efficiency of oil recovery. Production profiling is a technique in which a test instrument is lowered from the tubing to the bottom of the well to measure flow, temperature, pressure, and density in a multi-layer section of a producing well. Normal production profiling process needs to stop production, operate complex, consume long time and high cost. Furthermore, the profile cannot be continuously monitored for a long time. To address these limitations, this paper proposes a production profiling interpretation method based on reservoir primitive microbial DNA sequencing. The microbial stratigraphic baseline with high-resolution features is obtained by sampling and DNA sequencing of produced fluid and cuttings from different wells. Specifically, the random forest algorithm is preferred and improved by comparing the accuracy, precision, recall, F1-score, and running time of three clustering methods: Naïve-Bayes classifier, random forest classifier, and back-propagation classifier. Constructing PSO-random forest model is based on stratigraphic records and produced fluid bacteria features. The computational accuracy and efficiency of this method allows it to describe the production profile for each formation. Moreover, this test process does not need to stop production with simple operation and does not pollute the formation. Meanwhile, by sampling fluid production at different stages, it can achieve the purpose of long-term effective dynamic monitoring of the reservoir.

Changes in sociability of shelter cats

This study was conducted for the purpose of long-term monitoring of changes in the sociability of group-housed cats towards a familiar caregiver in a private no-kill shelter. The sociability of the monitored cat population was assessed at two-week intervals during one calendar year. A total of 158 animals were rated on a 5-point scale, the individual levels of which represented the level of sociability (1-very friendly cat to 5-very unfriendly cat). The evaluation was performed by visual observation of the cats' response to human approach and contact by one observer. At the first assessment, more than three quarters of the cats (81%) showed very friendly (score of 1) or friendly behavior (score of 2). Of the 88 cats that were evaluated at least twice and at the same time their stay in the shelter terminated during the monitoring period, 56 cats (63.6%) did not change their score (worsen or improve) during their stay in the shelter. Among the cats with an observed change, there was a permanently improved score in a significantly higher number of cats (P < 0.001) during the stay in the shelter than a permanent deterioration (26; 29.5% and 3; 3.4%, respectively). There was a temporary improvement or worsening of the score in 3 cats (3.4%). The improvement in the sociability score during the stay in the shelter mainly concerned cats whose behavior was rated as neutral (score of 3), unfriendly (score of 4) or very unfriendly (score of 5) at the first evaluation. The length of stay of cats in the shelter (LOS) correlated with the level of sociability of the cats during the first (rtau = 0.72, P < 0.001) and the last evaluation (rtau = 0.23, P = 0.007); however, the LOS itself did not predict the level of sociability (P > 0.05). The sociability level at the first assessment was found to be a predictor of the sociability level at the last assessment (P < 0.001). The results of our study suggest that during the stay in the shelter, the cats generally improve their sociability towards a familiar person. Although it appears that cats with lower levels of sociability remain in the shelter for a longer period of time, improvements may increase their adoption potential. Support for programs to increase the cat sociability is needed and should be addressed in further research.

Calibration of Electrical Resistance to Moisture Content for Beech Laminated Veneer Lumber “BauBuche S” and “BauBuche Q”

Electrical resistance measurements are often employed for the purpose of nondestructive long-term monitoring of wood moisture content (MC) in timber structures. As a structural material for high-performance load-bearing applications in such structures, beech laminated veneer lumber (LVL) enjoys a growing popularity. However, due to the processing of beech LVL affecting physical properties, calibration curves for bulk beech wood cannot be used. In this study, resistance was measured on 160 beech LVL samples equilibrated in four different relative humidity (RH) climates. The results show a difference not only between the beech LVL products “BauBuche S” and “BauBuche Q”, but also between measurements at two different depths. For each data set, parameters for calibration models using two and using three model parameters were determined by regression analysis to MC determined by the gravimetric method.

Classification mapping of salt marsh vegetation by flexible monthly NDVI time-series using Landsat imagery

Salt marshes are deemed as one of the most dynamic and valuable ecosystems on Earth. Recently, salt marsh deterioration and loss have become widespread because of anthropogenic stressors and sea level rise. Long-term acquisition of spatial information on salt marsh vegetation communities is thus critical to detect the general evolutionary trend of marsh ecosystems before irreversible change occurs. Medium resolution imagery organized in inter-annual time series has been proven suitable for large-scale mapping of salt marsh vegetation. For long-term monitoring purpose, the challenge still lies in developing time series based on data with sparse and uneven temporal distribution. This paper proposes a flexible Monthly NDVI Time-Series (MNTS) approach to achieve multi-temporal classification maps of salt marsh vegetation communities in the Virginia Coast Reserve, USA, by utilizing all viable Landsat TM/ETM + images during the period 1984–2011. Salt marsh vegetation communities are identified on a reference MNTS spanning 12 months with an overall accuracy of 0.898, approximately 0.107 higher than classifications using single images. Utilizing a flexible selection process based on the reference MNTS, a significant inverse hyperbolic relationship emerges between overall accuracy and average length of the time series. Based on these results, eight classification maps with average accuracy of 0.844 and time interval of 2–5 years are acquired. A spatio-temporal analysis of the maps indicates that the upper low marsh vegetation community has diminished by 19.4% in the study period, with a recent acceleration of losses. The conversion of marsh area to vegetation communities typical of low elevations (37.7 km2) is more than twice the conversion to vegetation communities typical of high elevations (18.3 km2), suggesting that salt marsh ecosystems at the Virginia Coast Reserve are affected by sea level rise.

Fashionable wrist band using highly conductive fabric for electrocardiogram signal monitoring

In this paper, a flexible and wearable fabric-based and highly conductive wrist band with portable electrocardiogram (ECG) equipment is presented for the long-term monitoring of ECG signals. The impedance properties, skin irritation, and sensitivity are then investigated using the proposed wrist band. The wrist band was constructed using conductive fabric, a Velcro strap, a metal snap, and a nickel connector. The entire polyester fabric surface was coated with nickel, copper, and gold. The sheet resistance of the conductive fabric is 0.06 Ω/sq. It is appropriate to use a dry fabric electrode for long-term monitoring purposes, rather than a gel-based Ag/AgCl electrode. The proposed system does not require additional active electrodes, and a single-layer standard printed circuit board (PCB) was developed to allow for portable ECG signal acquisition. We measured the impedance as per the frequency change and compared the outcomes with those of Ag/AgCl electrodes. Subsequently, we measured the ECG signal and investigated the possible artifacts caused by motion. The skin-electrode impedance of the wrist band was measured and compared to the Ag/AgCl electrodes, where we found a lower impedance for the wrist band electrodes. In addition, the power spectrum of the biopotential signals obtained from the wrist band electrodes are evaluated and compared to those obtained with Ag/AgCl electrodes for estimating signal quality. The experimental results show that the proposed electrode can successfully acquire an ECG signal from the wrist when the subject is resting and fewer motion artifacts are shown when the subject moves, rendering the proposed electrode comparable with the traditional disposable and gelled Ag/AgCl electrodes.

E. Torroja’s bridge: Tailored experimental setup for SHM of a historical bridge with a reduced number of sensors

This paper presents the design of an experimental setup with a reduced number of sensors for the structural health monitoring of the historical bridge of Posadas (Córdoba, Spain), designed by the eminent engineer Eduardo Torroja in 1957. The motivation of this study stems from the need for safeguarding this piece of cultural heritage. In particular, the singularity of this historical construction, a steel–concrete composite typology consisting of a concrete deck slab and inverted bowstring steel trusses, makes continuous in-service condition assessment essential for its maintenance. Nevertheless, the application of existing continuous monitoring systems to such large-scale structures entails considerable investments as well as complex signal processing algorithms. Whereby the optimization of the number of sensors and their location is of the utmost interest. In this line, this work presents the application of an Optimal Sensor Placement (OSP) methodology to tailor an experimental setup for a cost-efficient continuous monitoring of the E. Torroja’s bridge. Due to the fact that most OSP approaches are model-based, it is essential to count on a sufficiently accurate numerical model. To this aim, an extensive vibration-based operational modal analysis is first conducted with a large number of accelerometers. Afterward, a three-dimensional finite element model of the E. Torroja’s bridge is updated on the basis of the experimentally identified dynamic properties with a genetic optimization algorithm. Finally, an optimal sensor placement methodology is utilized to design an experimental setup with a limited number of sensors for long-term monitoring purposes. The results demonstrate that few sensors are needed to accurately assess the main resonant frequencies and mode shapes.

Elastic plastic approximation procedure for notched bodies subjected to thermal transient loadings

Components of power plants are often subjected to thermo-mechanical loading conditions. Thermal loadings alone are strain-controlled loadings, inducing locally high mechanical strains and stresses, which may result in low cycle fatigue issues. Furthermore, these cycles are mixed with numerous cycles of lower stress and strain ranges. Regarding applicable design codes such as ASME, French RCC-M or German KTA, fatigue evaluation of such components can be based on the simplified elastic plastic fatigue analysis as the standard option and alternatively on elastic plastic finite element analysis. With regard to processing of long load-time histories (e.g. within an online or offline fatigue monitoring approach), elastic plastic finite element analyses are too time-consuming and not feasible. In contrast, the simplified elastic plastic fatigue analysis is a comparatively fast method, but may yield overly conservative results (and in some rare cases underestimate elastic plastic strain ranges). This may lead to unsatisfactory results by neglecting important influences (cyclic plastic deformation behavior, load sequence and mean stress). In order to consider effects of load sequence and mean stress in fatigue evaluation, it is necessary to calculate the local stress-strain paths over the entire load-time history, using the elastic plastic deformation behavior of the material. The application of commonly used notch approximation procedures (e.g. Neuber’s rule, equivalent strain energy density method) fail under thermo-mechanical loading conditions by overestimating the local stresses and strains.As a general application e.g. for the purpose of long-term fatigue monitoring, measured or calculated temperature-time sequences have to be transferred to fatigue relevant stress and strain time sequences at critical locations. In order to support this task, a fast approximation procedure will be developed in order to overcome the shortcomings of plasticity estimation as an essential part of the fatigue analysis.

(Landscape monitoring and assessment in Sirte (Libya

إن تغير الظروف الإيكولوجية والاجتماعية والاقتصادية يجعل تدهور الأراضي، مصدر قلقٍ كبيرٍ في منطقة البحر المتوسط. يهدف هذا البحث إلى دراسة الأنماط المكانيَّة والزّمانية لديناميكيّات الغطاء الأرضي، وتحديد معدل واتجاه هذه لديناميكيّات في محافظة سرت (ليبيا)، ومراقبة التَّصحُّر وتقييمه فيها اعتماداً على تقنيَّة الاستشعار عن بعد، ونُظُم المعلومات الجغرافيَّة، من خلال استخدام مُنتَجي الغطاء الأرضي(MCD12Q1 ) لعام 2001 و2014، وقيم مؤشِّر NDVI (MOD13A3) من بيانات MODID/TERRA من سنة 2001- وحتَّى 2014 وكذلك وبيانات الهطول TRMM الأمطار للفترة 2001-2014. وقد أظهرت النتائج انخفاضاً في الكثبان الرَّملية الثَّابتة، والكثبان الرَّملية الشبه ثابتة بمعدل تغيير قدره 15.66 و 116.37 كم 2 في السَّنة على التَّوالي، إلَّا أنه لا يوجد للاتجاه أي دلالةٍ إحصائيَّة. وفي الوقت نفسه ازداد الغطاء النباتي بمعدل زيادة 112 كم 2 في السَّنة وبدون دلالة إحصائيَّة كذلك. كما أظهرت النتائج أنَّه لا يوجد اتجاه ذو دلالةٍ إحصائيَّةٍ لتراجع التَّصحُّر، إذ انخفضت مناطق التَّصحُّر الشَّديدة والمتوسطة بنحو (25٪) خلال فترة الدِّراسة. وبناء عليه فلا يزال من الضَّروريِّ مواصلة رصد وتقييم الأراضي المُتصحِّرة باستخدام الاستشعار عن بعد ولفترات طويلة الأجل، إضافة إلى إدارة البيئات الهشة في المنطقة حتى نتمكن من تحديد التغيرات في ديناميكية الغطاء النباتي.

NEW COASTAL VIDEO-MONITORING SYSTEM ACHIEVEMENT AND DEVELOPMENT

A new coastal video monitoring system for Apulia region, southeast of Italy, is under development. It is composed of visible and thermal streams and featured to be included in a wider meteo-oceanographic monitoring network. The system is designed for use on sandy beaches. The regional Basin Authority (AdBP) through previous field campaigns has identified for long-term monitoring purposes two hotspots, prone to erosion and flooding: Torre Canne (Fasano, BR) and Torre Lapillo (Porto Cesareo, LE), facing the Adriatic and Ionian seas, respectively. This paper presents the actual architecture and some initial findings of its implementation aiming at a complete automatic analysis of morphological features and hydrodynamic studies, mainly focused in swash zone.

An FIM-Based Long-Term In-Vial Monitoring System for Drosophila Larvae.

Drosophila larvae are an insightful model and the automated analysis of their behavior is an integral readout in behavioral biology. Current tracking systems, however, entail a disturbance of the animals, are labor-intensive, and cannot be easily used for long-term monitoring purposes. Here, we present a novel monitoring system for Drosophila larvae, which allows us to analyze the animals in cylindrical culture vials. By utilizing the frustrated total internal reflection in combination with a multi-camera/microcomputer setup, we image the complete housing vial surface and, thus, the larvae for days. We introduce a calibration scheme to stitch the images from the multi-camera system and unfold arbitrary cylindrical surfaces to support different vials. As a result, imaging and analysis of a whole population can be done implicitly. For the first time, this allows us to extract long-term activity quantities of larvae without disturbing the animals. We demonstrate the capabilities of this new setup by automatically quantifying the activity of multiple larvae moving in a vial. The accuracy of the system and the spatio-temporal resolution are sufficient to obtain motion trajectories and higher level features, such as body bending. This new setup can be used for in-vial activity monitoring and behavioral analysis and is capable of gathering millions of data points without both disturbing the animals and increasing labor time. In total, we have analyzed 107 671 frames resulting in 8650 trajectories, which are longer than 30 s, and obtained more than 4.2 × 106 measurements.

Dynamic response of an innovative hybrid structure in hardwood

In the context of the development and promotion of innovative and efficient hybrid timber structures, a pilot building, the ETH House of Natural Resources, has been designed. The building comprises three innovative structural systems, a post-tensioned timber frame, a composite beech laminated veneer lumber–concrete floor and a biaxial timber slab made of cross-laminated timber and beech laminated veneer lumber. The building will serve as an office building for the laboratory of hydraulics, hydrology and glaciology of ETH Zurich; as a ‘living lab’ for the implementation of a permanent sensor network for long-term monitoring purposes; and as a setup for a field testing campaign of in situ tests at different construction stages. Results of the first two series of this testing campaign and the derived modal characteristics of the structure are presented in this paper. The obtained modal data will extend the knowledge base on innovative hybrid timber structures and help to predict structural response for the case of significant loads such as high wind loads or earthquakes, through an extended model element updating procedure.

Two fixed ratio dilutions for soil salinity monitoring in hypersaline wetlands.

Highly soluble salts are undesirable in agriculture because they reduce yields or the quality of most cash crops and can leak to surface or sub-surface waters. In some cases salinity can be associated with unique history, rarity, or special habitats protected by environmental laws. Yet in considering the measurement of soil salinity for long-term monitoring purposes, adequate methods are required. Both saturated paste extracts, intended for agriculture, and direct surface and/or porewater salinity measurement, used in inundated wetlands, are unsuited for hypersaline wetlands that often are only occasionally inundated. For these cases, we propose the use of 1:5 soil/water (weight/weight) extracts as the standard for expressing the electrical conductivity (EC) of such soils and for further salt determinations. We also propose checking for ion-pairing with a 1:10 or more diluted extract in hypersaline soils. As an illustration, we apply the two-dilutions approach to a set of 359 soil samples from saline wetlands ranging in ECe from 2.3 dS m-1 to 183.0 dS m-1. This easy procedure will be useful in survey campaigns and in the monitoring of soil salt content.

An innovative nonintrusive driver assistance system for vital signal monitoring.

This paper describes an in-vehicle nonintrusive biopotential measurement system for driver health monitoring and fatigue detection. Previous research has found that the physiological signals including eye features, electrocardiography (ECG), electroencephalography (EEG) and their secondary parameters such as heart rate and HR variability are good indicators of health state as well as driver fatigue. A conventional biopotential measurement system requires the electrodes to be in contact with human body. This not only interferes with the driver operation, but also is not feasible for long-term monitoring purpose. The driver assistance system in this paper can remotely detect the biopotential signals with no physical contact with human skin. With delicate sensor and electronic design, ECG, EEG, and eye blinking can be measured. Experiments were conducted on a high fidelity driving simulator to validate the system performance. The system was found to be able to detect the ECG/EEG signals through cloth or hair with no contact with skin. Eye blinking activities can also be detected at a distance of 10cm. Digital signal processing algorithms were developed to decimate the signal noise and extract the physiological features. The extracted features from the vital signals were further analyzed to assess the potential criterion for alertness and drowsiness determination.

Calibration and performance of the photon sensor response of FACT — the first G-APD Cherenkov telescope

The First G-APD Cherenkov Telescope (FACT) is the first in-operation test of the performance of silicon photo detectors in Cherenkov Astronomy. For more than two years it is operated on La Palma, Canary Islands (Spain), for the purpose of long-term monitoring of astrophysical sources. For this, the performance of the photo detectors is crucial and therefore has been studied in great detail. Special care has been taken for their temperature and voltage dependence implementing a correction method to keep their properties stable. Several measurements have been carried out to monitor the performance. The measurements and their results are shown, demonstrating the stability of the gain below the percent level. The resulting stability of the whole system is discussed, nicely demonstrating that silicon photo detectors are perfectly suited for the usage in Cherenkov telescopes, especially for long-term monitoring purpose.

Structural health monitoring of a cable-stayed bridge with Bayesian neural networks

In recent years, there has been an increasing interest in permanent observation of the dynamic behaviour of bridges for long-term monitoring purpose. This is due not only to the ageing of a lot of structures, but also for dealing with the increasing complexity of new bridges. The long-term monitoring of bridges produces a huge quantity of data that need to be effectively processed. For this purpose, there has been a growing interest on the application of soft computing methods. In particular, this work deals with the applicability of Bayesian neural networks for the identification of damage of a cable-stayed bridge. The selected structure is a real bridge proposed as benchmark problem by the Asian-Pacific Network of Centers for Research in Smart Structure Technology (ANCRiSST). They shared data coming from the long-term monitoring of the bridge with the structural health monitoring community in order to assess the current progress on damage detection and identification methods with a full-scale example. The data set includes vibration data before and after the bridge was damaged, so they are useful for testing new approaches for damage detection. In the first part of the paper, the Bayesian neural network model is discussed; then in the second part, a Bayesian neural network procedure for damage detection has been tested. The proposed method is able to detect anomalies on the behaviour of the structure, which can be related to the presence of damage. In order to obtain a confirmation of the obtained results, in the last part of the paper, they are compared with those obtained by using a traditional approach for vibration-based structural identification.

Impacts of agricultural irrigation on nearby freshwater ecosystems: The seasonal influence of triazine herbicides in benthic algal communities

A small hydrological basin (Lerma, NE Spain), transformed from its natural state (steppe) to rain-fed agriculture and recently to irrigation agriculture, has been monitored across four seasons of an agricultural year. The goal of this study was to assess how and whether agricultural activities impacted the nearby freshwater ecosystems via runoff. Specifically, we assessed the toxicity of three triazine herbicides, terbuthylazine, atrazine and simazine on the photosynthetic efficiency and structure of algal benthic biofilms (i.e., phototropic periphyton) in the small creek draining the basin. It was expected that the seasonal runoff of the herbicides in the creek affected the sensitivity of the periphyton in accord with the rationale of the Pollution Induced Community Tolerance (PICT): the exposure of the community to pollutants result in the replacement of sensitive species by more tolerant ones. In this way, PICT can serve to establish causal linkages between pollutants and the observed biological impacts.The periphyton presented significantly different sensitivities against terbuthylazine through the year in accord with the seasonal application of this herbicide in the crops nowadays. The sensitivity of already banned herbicides, atrazine and simazine does not display a clear seasonality. The different sensitivities to herbicides were in agreement with the expected exposures scenarios, according to the agricultural calendar, but not with the concentrations measured in water, which altogether indicates that the use of PICT approach may serve for long-term monitoring purposes. That will provide not only causal links between the occurrence of chemicals and their impacts on natural communities, but also information about the occurrence of chemicals that may escape from traditional sampling methods (water analysis). In addition, the EC50 and EC10 of periphyton for terbuthylazine or simazine are the first to be published and can be used for impact assessments.

Characterization of spatial patterns in river water quality using chemometric pattern recognition techniques

This study employed three chemometric data mining techniques (factor analysis (FA), cluster analysis (CA), and discriminant analysis (DA)) to identify the latent structure of a water quality (WQ) dataset pertaining to Kinta River (Malaysia) and to classify eight WQ monitoring stations along the river into groups of similar WQ characteristics. FA identified the WQ parameters responsible for variations in Kinta River’s WQ and accentuated the roles of weathering and surface runoff in determining the river’s WQ. CA grouped the monitoring locations into a cluster of low levels of water pollution (the two uppermost monitoring stations) and another of relatively high levels of river pollution (the mid-, and down-stream stations). DA confirmed these clusters and produced a discriminant function which can predict the cluster membership of new and/or unknown samples. These chemometric techniques highlight the potential for reasonably reducing the number of WQVs and monitoring stations for long-term monitoring purposes.

Yellow-eyed Penguin (Megadyptes antipodes) as a case study to assess the reliability of nest counts

Population monitoring of seabirds plays an important role in conservation since it provides the information required to evaluate conservation programmes of endangered species, to guide harvest management and to monitor indicators of marine ecosystem health. Annual nest counts are often used for the long-term monitoring of breeding seabird populations. While such counts provide a direct and cost-effective survey method, single nest counts will almost always yield an underestimate of the true number of nests and provide no means of expressing uncertainty. In this study, we used double counts and the Lincoln–Petersen estimator to assess the reliability of nest counts for the Yellow-Eyed Penguin (Megadyptes antipodes) in the South Island of New Zealand. We estimated the detection rate of single nest counts at 88%, and we calculated that double counts are sufficiently precise to detect changes in the size of the breeding population as small as 3.3% between years. We failed to detect observer bias or any effects of search effort or habitat on the detection rate, the only significant factor being the steepness of the terrain. Given the high detection rate and the susceptibility of Yellow-Eyed Penguins to human disturbance, we conclude that the established protocol for single nest counts is adequate for the regular monitoring of the population. We suggest that double counts could be conducted once every 5 years to obtain precise estimates for the purpose of long-term population monitoring. We also highlight the importance of repeating similar studies for a variety of species and habitats.