Roof Heights Research Articles

Sat2Map: Reconstructing 3D Building Roof from 2D Satellite Images

Three-dimensional (3D) urban models have gained interest because of their applications in many use cases, such as disaster management, energy management, and solar potential analysis. However, generating these 3D representations of buildings require lidar data, which is usually expensive to collect. Consequently, the lidar data are not frequently updated and are not widely available for many regions in the US. As such, 3D models based on these lidar data are either outdated or limited to those locations where the data is available. In contrast, satellite images are freely available and frequently updated. We propose sat2Map , a novel deep learning-based approach that predicts building roof geometries and heights directly from a single 2D satellite image. Our method first uses sat2pc to predict the point cloud by integrating two distinct loss functions, Chamfer Distance and Earth Mover’s Distance, resulting in a 3D point cloud output that balances overall structure and finer details. Additionally, we introduce sat2height , a height estimation model that estimates the height of the predicted point cloud to generate the final 3D building structure for a given location. We extensively evaluate our model on a building roof dataset and conduct ablation studies to analyze its performance. Our results demonstrate that sat2Map consistently outperforms existing baseline methods by at least 18.6%. Furthermore, we show that our refinement module significantly improves the overall performance, yielding more accurate and fine-grained 3D outputs. Our sat2height model demonstrates a high accuracy in predicting height parameters with a low error rate. Furthermore, our evaluation results show that we can estimate building heights with a median mean absolute error of less than 30 cm while still preserving the overall structure of the building.

The Evaluation on Thermal Performance of Rumah Negeri Sembilan Berserambi Dua dan Beranjung

Traditional Malay house, a passive design architecture, is believed to have more effective thermal performance than modern residential houses through climatic design strategies. Unfortunately, the Malay house has experienced numerous changes and is confronted with constant dangers due to present-day science and innovation. Thus, this study aimed at evaluating the thermal performance of rumah Negeri Sembilan berserambi dua dan beranjung for sustainable practice in the tropical environment. The method used was fieldwork: observation and thermal measurement. Comparing the suggested comfort level by ASHRAE 55 and ICOP, 20% percent of the total data is falls within the thermal comfort range suggested. However, the house is considered in comfort environment between 25-27ºC, which is only in the early morning. As for the wind flow, each house division recorded different readings. However, it was still within the comfort level range, i.e., between 0.12-1.25m/s, while the RH level was 50-60%. Therefore, the primary findings elaborate that the Malay house construction has five factors that directly influence the house's thermal performance. These include floor areas, openings, floor and roof heights, materials, open compound areas, and building setting. This study aspires to provide useful insights regarding the effectiveness of practices in the climatic design strategies of a traditional Malay house. Thus, its contribute to the scientific discussions on sustainable practices in modern residential design which aligned with the Twelfth Malaysia Plan (RMK12) Theme 3.

Head excursions of rearward-facing child restraint systems in rear impacts

Objective The aim of the current study was to quantify the head excursions of pediatric anthropomorphic test devices (ATDs) seated in rearward-facing child restraint system (CRS) models during rear impact sled tests and compare to roof heights of vehicles in the current fleet to assess the possibility of head contact against the vehicle roof. Methods Head excursions of ATDs seated in rearward-facing CRS models were analyzed from high-speed video data from 14 rear impact sled tests across two different series. Tests were conducted in rigidized vehicle seats from recent model year vehicles. Rearward-facing infant and convertible CRS models were tested with a variety of pediatric ATDs aged 12 months to 6 years in a variety of installation conditions (e.g., lower anchors or seat belt, anti-rotation features, etc). Maximum ATD head excursions in plane of the seatback were compared to previously measured roof heights of 87 different vehicles. Results The roof heights in all sedan seating positions (n = 58) and SUV/CUV/minivan seating positions (n = 60) were greater than the largest maximum ATD head excursions in plane of the seatback (792 mm). Head contact was possible in two of the pickup trucks which had roof heights of 730 and 775 mm. In all, 98% of vehicle seating positions measured in this study would accommodate all of the maximum ATD head excursions in plane of the seatback without contact. Conclusions The risk of head contact against the vehicle interior roof appears low as maximum ATD head excursions in plane of the seatback were typically not great enough to reach the rooflines of the vehicles in the sample. Head contact appears possible in pickup trucks, where the window/roofline is directly behind the head restraint.

Multivariate analysis identifying the main factors associated with cow productivity and welfare in tropical smallholder dairy farms in Vietnam

This study aimed to rank potential drivers of cow productivity and welfare in tropical smallholder dairy farms (SDFs) in Vietnam. Forty-one variables were collected from 32 SDFs located in four geographically diverse dairy regions, with eight SDFs per region. Twelve variables, including milk yield (MILK), percentages of milk fat (mFA), protein (mPR), dry matter (mDM), energy-corrected milk yield (ECM), heart girth (HG), body weight (BW), ECM per 100 kg BW (ECMbw), body condition score (BCS), panting score (PS), inseminations per conception (tAI), and milk electrical resistance (mRE) of cows, were fitted as outcome variables in the models. Twenty-one other variables describing farm altitude, housing condition, and diet for the cows, cow genotypes, and cow physiological stage were fitted as explanatory variables. Increased farm altitude was associated with increases in ECM and mRE and with decreases in PS and tAI (P < 0.05). Increases in roof heights and percentage of shed side open were associated with increases in ECM, mFA, and mDM (P < 0.05). Increased dry matter intake and dietary densities of dry matter and fat were associated with increased MILK, ECM, and ECMbw and decreased tAI (P < 0.05). Increased dietary lignin density was associated with increased PS. Increased genetic proportion of Brown Swiss in the herd was associated with increased MILK, ECM, and ECMbw (P < 0.05). Thus, to improve cow productivity and welfare in Vietnamese SDFs, the following interventions were identified for testing in future cause-effect experiments: increasing floor area per cow, roof heights, shed sides open, dry matter intake, dietary fat density, and the genetic proportion of Brown Swiss and decreasing dietary lignin density.

Evaluating the Cooling Performance of Green Roofs Under Extreme Heat Conditions

The local rise in urban temperature is increasingly exacerbated due to the combined effect of urban heat islands and global climate change. Numerous studies have shown that green roofs (GRs) have great potential for facilitating urban heat mitigation. However, little is known about whether such cooling effects can be achieved under extreme heat conditions. With the expected occurrence of more extreme heat events under climate change, such understanding is crucially important for the effective design of heat mitigation. This study aims to fill this gap by investigating the pedestrian-level cooling effect of GR under two weather conditions (i.e., typical summer weather conditions and extreme heat conditions). This research employed a three-dimensional simulation model, ENVI-met, to simulate pedestrian-level air temperature for three typical residential areas with different roof heights in Beijing. We conducted the simulations in two different roof scenarios, conventional roofs versus green roofs. The results showed that green roofs could provide large cooling exceeding 0.2°C on downwind sides and in the daytime, although the average cooling intensity was small. The pedestrian-level cooling intensity of GR decreased significantly under extreme heat conditions compared to typical summer weather conditions. It varied diurnally following an inverted W-shape for both weather conditions. Results also showed that the pedestrian-level cooling intensity of GR decreased with the increase in roof height in a nonlinear way and became 0 when roof height reached ∼50 m for both weather conditions. The results of our research can provide important insights for cooling-oriented urban design in the future, as we are expecting such extreme weather conditions nowadays may be the new normal in the future.

The role of surrounding buildings on the accumulation of embers on rooftops during an ember storm

Results are presented for tests of ember accumulation on buildings during an ember storm. Specifically, the experiments investigate the role of upstream buildings on the accumulation of embers on the rooftops of a building. Experiments were run for three target buildings for three different wind directions per building. The upstream array of buildings varied in both layout (staggered and regular grids of buildings) and in terms of the number of upstream rows of buildings and streamwise spacing between the buildings. Results indicate that each of these parameters, i.e. spacing, layout, and number of rows, influences the accumulation rate. In all cases tested the mass of embers that accumulated on the rooftops was less than 18% of the mass that would have accumulated were the building removed. For buildings with roof heights similar to those of the upstream buildings the accumulation rate increases by up to a factor of 10 compared to when there are no upstream buildings. The lowest spacing between buildings produced the largest accumulation. When the target building roof height was larger than upstream buildings, this change was less pronounced. However, the variability in the accumulation rate between nominally identical tests decreased when the upstream buildings were present.

Mine conveyor belt fire classification

This article presents a conveyor belt fire classification model that allows for the determination of the most effective firefighting strategy. In addition, the effect of belt design parameters on the fire classification was determined. A methodology that involves the use of numerical simulations and artificial neural networks was implemented. An approach previously proposed for modeling fires over conveyor belts was used. With the objective of obtaining some required modeling input parameter and verifying the capacity of this approach to get realistic results, computational fluid dynamics model calibration and validation were carried out using experimental test results available in the literature. Results indicated that scenarios with belt positions closer to the mine roof and greater tunnel heights require a higher longitudinal air velocity to be attacked directly. Furthermore, the belt fire classification model provided by the artificial neural network had an accuracy around 95% when test scenarios were classified.

The combining effect of the roof shape, roof-height non-uniformity and source position on the pollutant transport between a street canyon and 3D urban array

Although most people live in cities, the pollutant transport in so-called street canyons is still not well understood. The main reason is the complexity of the problem, where the roof shape, roof height and position of the pollutant source within a 3D urban array may play a significant role. This paper tries to improve the understanding and investigates the pollutant transport in six different types of street canyons using large-eddy simulations (LES). All street canyons were part of four different 3D urban arrays and differed in the roof shape and height. The results demonstrate that roof shape, roof-height non-uniformity, and the source position have a crucial impact on the advective and turbulent pollutant transport between the studied canyons and urban arrays. Both the flat roofs and roof-height variability enhance the lateral transport between the street canyons and intersections irrespective of the studied cases. This is crucial for the evaluation of the street canyon pollution if one changes the position of the source within the non-uniform urban array. Although the differences in the pollutant transport between the flat and pitched roofs mitigate in the cases of the variable roof heights, they are still appreciable.

A wind tunnel study on three-dimensional buoyant flows in street canyons with different roof shapes and building lengths

Higher temperatures are measured in urban areas compared to surrounding rural areas due to the urban heat island effect. One of the most efficient ways of removing heat from urban areas is wind-driven ventilation. Building configurations have a strong impact on the wind flow patterns and therefore on the heat removal from urban areas. Buoyancy can promote heat removal by inducing three-dimensional flow structures. This prevents the formation of standing vortices in street canyons, which are formed for forced convective flow regimes and trap heat inside the street canyons. A wind tunnel study is conducted for street canyons in an urban area. The wind tunnel floor is heated to different temperatures to induce buoyancy. The flow structures are measured with PIV (Particle Image Velocimetry) on horizontal and vertical planes within the street canyon and the air temperatures are measured with an approach based on infrared thermography. The flows entering the street canyon through the lateral sides are measured on a horizontal PIV plane. These lateral flows can be found for buoyancy driven flows and are important, since they prevent the formation of standing vortices. To improve the heat removal in forced convective flows, different roof shapes and heights are studied and the lengths of the street canyon buildings are varied. The results show that lateral flows can be found for street canyons with non-uniform building heights and that the air temperatures are decreased in such street canyons due to the improved ventilation.

Pressure Losses in Solar Chimney Power Plant

This technical brief develops a theoretical model of all the pressure losses in the solar chimney power plant (SCPP, also called solar updraft power plant) and analyzes the pressure losses for different chimney internal stiffening appurtenance (SA) structures, different roof heights, and different collector support parameters. Results show that the exit dynamic pressure drop (EDPD) accounts for the majority of the total pressure loss (TPL), while other losses constitute only small proportions of the TPL, and the collector inlet loss is negligible. Pressure losses are strongly related to the mass flow rate, while reasonable mass flow rates excluding too low flow rates have little influence on the pressure loss ratios (PLRs, defined as the ratios of the pressure losses to the TPL) and the total effective pressure loss coefficient (TEPLC). Designing of the SA structure in view of reducing the drag, for example, using the ring stiffeners without wire spoked instead of the spoked bracing wheels (SBWs), reducing the width of the chimney internal rims of SAs, or reducing the number of SAs results in large reduction of the SA PLR and the TPL. Lower roof leading to higher velocity inside the collector, larger supports, or shorter intersupport distance leads to the increase in the support PLR. This technical brief lays a solid foundation for optimization of SCPPs in future.

How tall buildings affect turbulent air flows and dispersion of pollution within a neighbourhood.

The city of London, UK, has seen in recent years an increase in the number of high-rise/multi-storey buildings ("skyscrapers") with roof heights reaching 150m and more, with the Shard being a prime example with a height of ∼310m. This changing cityscape together with recent plans of local authorities of introducing Combined Heat and Power Plant (CHP) led to a detailed study in which CFD and wind tunnel studies were carried out to assess the effect of such high-rise buildings on the dispersion of air pollution in their vicinity. A new, open-source simulator, FLUIDITY, which incorporates the Large Eddy Simulation (LES) method, was implemented; the simulated results were subsequently validated against experimental measurements from the EnFlo wind tunnel. The novelty of the LES methodology within FLUIDITY is based on the combination of an adaptive, unstructured, mesh with an eddy-viscosity tensor (for the sub-grid scales) that is anisotropic. The simulated normalised mean concentrations results were compared to the corresponding wind tunnel measurements, showing for most detector locations good correlations, with differences ranging from 3% to 37%. The validation procedure was followed by the simulation of two further hypothetical scenarios, in which the heights of buildings surrounding the source building were increased. The results showed clearly how the high-rise buildings affected the surrounding air flows and dispersion patterns, with the generation of "dead-zones" and high-concentration "hotspots" in areas where these did not previously exist. The work clearly showed that complex CFD modelling can provide useful information to urban planners when changes to cityscapes are considered, so that design options can be tested against environmental quality criteria.

Effects of roof height on local pressure and velocity coefficients on building roofs

Failures of roofing systems occur due to high local suctions on tiles or shingles, or because of a different failure mechanism triggered by high local wind velocities near the roof surface. In the latter case, the local velocity can induce positive pressures on the lip of a windward facing shingle or tile, which are transmitted underneath, adding to the external surface negative pressure and causing an increase of the net uplift force. Building codes provide estimates of the peak pressure coefficients (peak Cp) based on 3-s gust in the oncoming wind at the roof height. As an approximation, these coefficients are generally taken to be independent of roof height and exposure. This implies that wind tests of roofing system behaviour carried out at one roof height can be used to infer the system behaviour for other roof heights. One of the main objectives of the present study was to examine the validity of this approximation. Regarding the second failure mechanism discussed above, knowledge of surface wind speed is a key element to assess the uplift forces on shingles. Building codes do not address the wind velocities close to the roof surface and estimate it based on the approach wind speed in terms of a wind speed ratio. So the second objective of the present research was to examine the ratio of local wind velocity close to the roof surface to the velocity at roof height in the approach flow and investigate the effect of height on the velocity ratios. Wind tunnel tests were performed on four different gable-hip roof buildings, at various wind directions. Both surface pressures and near-surface velocities were measured and normalized with respect to upwind flow conditions at mean roof height. The results confirm that the velocity ratios and peak Cp values on the gable roof do not vary markedly with building height with no more than 10% change found at most locations. For the velocity ratios a similar conclusion was reached on the hip roof. However, for the Cp values in the corner zones of the hip roofs increases with height were identified and further investigation is recommended.

Effect of roof height on microclimate and plant characteristics in an insect-proof screenhouse with impermeable sidewalls

An experiment was conducted to study the effect of structure height on air temperature and humidity, on air exchange rate and on transpiration and yield in an insect-proof screenhouse. Two houses with roof heights of 4 and 6 m, and impermeable polyethylene sheets on the sidewalls were examined. Air exchange with the outside environment took place only through the horizontal screened roof and tomato plants were grown in both houses. The results showed that the increase in screenhouse height from 4 to 6 m elicited almost no changes in daily mean air temperature, humidity ratio and consequently, in relative humidity within the canopy. However, it reduced by about 30% the airflow through the screenhouse and consequently the air exchange rate. Moreover, the increase in height did not elicit changes in crop transpiration, yield and plant development. Thus, it is concluded that in insect-proof screenhouses that are ventilated through the roof, there is no benefit in increasing structure height above the current common height of about 4 m.

Impacts of shape and height of building roof on airflow and pollutant dispersion inside an isolated street canyon

ABSTRACTTwo-dimensional numerical simulations were performed using the FLUENT code to investigate the impacts of the shape and height of building roofs on flow and pollutant dispersion inside an isolated street canyon. The numerical model was validated against wind tunnel measured data. Five different roof shapes (vaulted, trapezoidal, slanted, upward wedge-shaped, and downward wedge-shaped roofs) and three different roof heights ( = 1/6, 1/3, and 1/2, where is the roof height and H is the building height) were considered in the simulations. The numerical results revealed that the vortical flow structure and pollutant distribution within an isolated canyon depend significantly on the shape and height of building roofs. A large unique clockwise vortex is established in the canyon, and thus the pollutants accumulate in the leeward side of the canyon for the vaulted and downward wedge-shaped roofs at = 1/6, 1/3, and 1/2, the trapezoidal roof at = 1/6 and 1/3, and the slanted and upward wedge-shaped roofs at = 1/6, while an upper clockwise vortex and a lower counterclockwise vortex are generated, and consequently the pollutants pile up in the windward side of the canyon for the trapezoidal roof at = 1/2 and the slanted and upward wedge-shaped roofs at = 1/3 and 1/2. In the one-vortex flow regimes, the vortex center moves upwards and the vortex size expands vertically as the roof height increases for the vaulted, trapezoidal, and downward wedge-shaped roofs. In the two-vortex flow regimes, the size and rotational speed of both the upper clockwise and lower counterclockwise vortices increase with roof height for the slanted and upward wedge-shaped roofs. At each of the three roof heights examined, the lowest pollution level occurs in the canyon with the downward wedge-shaped roof, suggesting that the downward wedged-shaped roof is more beneficial for pollutant removal from the isolated canyon than the vaulted, trapezoidal, slanted, and upward wedge-shaped roofs. Due to the establishment of two-vortex flow structures, the trapezoidal roof at = 1/2, the slanted roof at = 1/3 and 1/2, and especially the upward wedge-shaped roof at = 1/3 and 1/2 are unfavorable for pollutant dispersion and dilution in the canyon compared to the vaulted and downward wedge-shaped roofs.

Gray algebraic curve model-based roof separation prediction method for the warning of roof fall accidents

Roof separation is one of the main precursors of coal mine accidents at the workface. At present, indicator data are usually read in an attempt to understand the real-time changes of the roof separation, but the change trend cannot be predicted. Predicting the change trend of roof separation on time can play a very important role in roof control. In this study, we apply the gray theoretical analysis method to predict the change trend of roof separation. We use Universal Distinct Element Code (UDEC) numerical simulation software to simulate the generation processes of roof separation. For this purpose, we consider four scenarios with different immediate roof heights. Using experimental separation data as original data, we predict roof separation using the gray algebraic curve model (GAM). The GAM-predicted data show little error when compared with the experimental data and are also better compared with prediction data obtained with the traditional gray model GM(1,1). Finally, in a case study using field-monitoring roof separation data from a mine, the GAM method led to good prediction results, and the predicted development trend reflected the real conditions. Thus, we prove that GAM is a very effective prediction method, which will be very useful in predicting roof separation trends for the warning of roof fall accidents.

Ventilation Processes in a Three-Dimensional Street Canyon

The ventilation processes in three different street canyons of variable roof geometry were investigated in a wind tunnel using a ground-level line source. All three street canyons were part of an urban-type array formed by courtyard-type buildings with pitched roofs. A constant roof height was used in the first case, while a variable roof height along the leeward or windward walls was simulated in the two other cases. All street-canyon models were exposed to a neutrally stratified flow with two approaching wind directions, perpendicular and oblique. The complexity of the flow and dispersion within the canyons of variable roof height was demonstrated for both wind directions. The relative pollutant removals and spatially-averaged concentrations within the canyons revealed that the model with constant roof height has higher re-emissions than models with variable roof heights. The nomenclature for the ventilation processes according to quadrant analysis of the pollutant flux was introduced. The venting of polluted air (positive fluctuations of both concentration and velocity) from the canyon increased when the wind direction changed from perpendicular to oblique, irrespective of the studied canyon model. Strong correlations ( $$>$$ 0.5) between coherent structures and ventilation processes were found at roof level, irrespective of the canyon model and wind direction. This supports the idea that sweep and ejection events of momentum bring clean air in and detrain the polluted air from the street canyon, respectively.

An experimental investigation on the requirement of roof height and sill width for car ingress and egress

This study aimed at experimentally investigating the influence of roof height and sill width on car ingress/egress movements. The first uncomfortable (Ht1) and the lowest acceptable (Ht2) roof heights were obtained from 26 participants of three different stature groups thanks to a multi-adjustable vehicle mock-up. Both Ht1 and Ht2 were affected neither by stature nor by vehicle type. Only a difference of 45 mm between Ht1 and Ht2 was observed. Tall volunteers more flexed the trunk and neck than short persons thanks to a larger space available around the seat when the head passing under the roof. The vehicle type had almost no effect on upper body posture. The roof height only affected neck flexion. The sill width mainly imposed a lateral translation. Results demonstrated that an appropriate roof height should be determined carefully. A small change of 45 mm in roof height may lead to an unacceptable situation. Practitioner Summary: The present study experimentally investigated the effects of roof height and sill width on car ingress and egress movements. Short females required almost the same roof height as tall males due to smaller space around the seat. The results would help to optimise car dimensions for improving car accessibility.

FITTING OF PARAMETRIC BUILDING MODELS TO OBLIQUE AERIAL IMAGES

Abstract. In literature and in photogrammetric workstations many approaches and systems to automatically reconstruct buildings from remote sensing data are described and available. Those building models are being used for instance in city modeling or in cadastre context. If a roof overhang is present, the building walls cannot be estimated correctly from nadir-view aerial images or airborne laser scanning (ALS) data. This leads to inconsistent building outlines, which has a negative influence on visual impression, but more seriously also represents a wrong legal boundary in the cadaster. Oblique aerial images as opposed to nadir-view images reveal greater detail, enabling to see different views of an object taken from different directions. Building walls are visible from oblique images directly and those images are used for automated roof overhang estimation in this research. A fitting algorithm is employed to find roof parameters of simple buildings. It uses a least squares algorithm to fit projected wire frames to their corresponding edge lines extracted from the images. Self-occlusion is detected based on intersection result of viewing ray and the planes formed by the building whereas occlusion from other objects is detected using an ALS point cloud. Overhang and ground height are obtained by sweeping vertical and horizontal planes respectively. Experimental results are verified with high resolution ortho-images, field survey, and ALS data. Planimetric accuracy of 1cm mean and 5cm standard deviation was obtained, while buildings' orientation were accurate to mean of 0.23° and standard deviation of 0.96° with ortho-image. Overhang parameters were aligned to approximately 10cm with field survey. The ground and roof heights were accurate to mean of – 9cm and 8cm with standard deviations of 16cm and 8cm with ALS respectively. The developed approach reconstructs 3D building models well in cases of sufficient texture. More images should be acquired for completeness of overhang results and automatic accuracy check of roof parameters.

A HYBRID APPROACH TO EXTRACTION AND REFINEMENT OF BUILDING FOOTPRINTS FROM AIRBORNE LIDAR DATA

Abstract. This work presents a combined bottom-up and top-down approach to extraction and refinement of building footprints from airborne LIDAR data. Building footprints are interesting for many applications in urban planning. The cadastral maps, however, may be limited for certain areas or not be updated frequently. Airborne laser scanning data is therefore considered by many people in the last decade as an important alternative data for change detection and update of building footprints. Laser scanning data of city scenes, however, often shows noise and incompleteness because of, e.g., the clutter by vegetation and the reflection of windows/waterlogged depressions on the roof. Results of the bottom-up detection may thus be limited to incomplete or irregular polygons. We employ 3D Hough transform to detect the building points. An improved joint multiple-plane detection scheme is proposed to find and label the laser points on multiple roof facets synchronously. The bottom-up processing provides not only a rough point segmentation but also additional 3D information, e.g., roof heights and horizontal ridges. Using these as priors, a top-down reconstruction is conducted via generative models. We consider the building footprint as an assembly of regular primitives. A statistical search by means of Reversible Jump Markov Chain Monte Carlo and Maximum A Posteriori estimation is implemented to find the optimal configuration of the footprint. By these means a robust and plausible reconstruction is guaranteed. First results on point clouds with various resolutions show the potential of this approach.

Sinus anatomy associated with inadvertent cerebrospinal fluid leak during functional endoscopic sinus surgery

Anatomic variations in skull base anatomy may predispose the surgeon to inadvertent skull base injury with resultant cerebrospinal fluid (CSF) leak during functional endoscopic sinus surgery (ESS). Our objective was to compare preoperative sinus imaging of patients who underwent FESS with and without CSF leak to elucidate these variations. In this retrospective case-control study, 18 patients with CSF leak following FESS for chronic rhinosinusitis (CRS) from 2000 to 2011 were compared to 18 randomly selected patients who underwent preoperative imaging for FESS for CRS. Measurements were obtained from preoperative computed tomography images with specific attention to anatomic differences in cribriform plate and ethmoid roof heights in the coronal plane, and the skull base angle in the sagittal plane. Mean values of measured variables were compared using a nonparametric Mann-Whitney test. When compared to controls, patients with CSF leak demonstrated a greater angle of the skull base in the sagittal plane (P < .001) and a greater slope of the skull base in the coronal plane (P < .006). A lower cribriform height relative to ethmoid roof height was also noted in cases of CSF leak as compared to controls (P < .04). A steep skull base angle in the sagittal plane, a greater slope of the skull base in the coronal plane, and a low cribriform height relative to the ethmoid roof predispose the patient to CSF leak during FESS. Preoperative review of imaging with specific attention paid to these anatomic variations may help to prevent iatrogenic CSF leak.