Acquisition d'images thermiques par drone : corrections radiométriques à partir de données terrain

Thermal images have many applications in agronomy, including crop water stress status assessment. Nowadays, the miniaturization of thermal cameras allows installing them onboard the Unmanned Aerial Vehicles (UAV), but this miniaturization leads to some difficulties: the miniaturized thermal cameras have no temperature control system of their sensor. The instability of the miniaturized camera makes a high drift in the acquisition of temperature data so that acquired thermal images don't fit the real temperature of the studying object, so data have to be continuously corrected. We need to have stable reference on field in order to compute the actual temperature value. In this article we present a method for radiometric correction of UAV remote sensed thermal images. We have implemented a device in order to retrieve ground temperature measurements. This device is composed with four targets (cold, hot, dry soil, wet soil) which measured continuously the target temperature thanks to IR120 (Campbell ®) radio-thermometer. A meteorological station is included in this ground system and acquires air temperature and moisture, solar radiation, wind speed and direction every 10 seconds. The images are radiometrically corrected by linear regression from on ground thermal data collected. Corrected images have been compared with mean canopy surface temperature of a sample of 10 trees measured with radio-thermometers. The results showed a good link between data from on ground radio-thermometer and data from thermal camera after radiometric correction. We can conclude that images obtained by this method are of sufficient quality to be used in vegetation water stress studies. (Résumé d'auteur

High resolution thermal and multispectral UAV imagery for precision assessment of apple tree response to water stress

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières(Edited by Pablo Gonzalez-de-Santos and Angela Ribeiro)This manuscript presents a comprehensive methodology to obtain Thermal, Visible and Near Infrared ortho-mosaics, as a previous step for the further image-based assessment of response to water stress of an experimental apple tree orchard. Using this methodology, multi-temporal ortho-mosaics of the field plot were created and accuracy of ortho-rectification and geo-location computed. Unmanned aerial vehicle (UAV) flights were performed on an irrigated apple tree orchard located in Southern France. The 6400 m² plot was composed of 520 apple trees which were disposed in 10 rows. In this field set-up, five well irrigated rows alternated with five rows submitted to progressive summer water constraints. For remote image acquisition, on 4th July, 19th July, 1st August and 6th September UAV flights with three cameras onboard (thermal, visible and near infrared) were performed at solar noon. On 1st August, five successive UAV flights were carried out at 8, 10, 12, 14 and 16 h (solar time). By using selfdeveloped software, frames were automatically extracted from the recorded thermal video and turned in the right image format. The temperature of four different targets (hot, cold, wet and dry bare soil) was continuously measured by the IR120 thermoradiometers during each flight, for radiometric calibration purpose. Based each on thirty images, all ortho-mosaics were successfully obtained. As high spatial resolution imagery requires high precision geo-location, and the root mean squared error (RMSE) of each ortho-mosaic positioning was calculated in order to assess its spatial accuracy. RMSE values were less than twice the pixel size in every case, which allowed a precise overlapping of the mosaics created. Canopy temperature data extracted from thermal images for showed significantly higher temperatures in water stressed trees compared to well irrigated, difference being related to severity of water stress. Thanks to the ultrahigh resolution of remote images obtained (<0.1m spatial resolution for thermal infrared images), and beyond its capacity to delineate efficiently each individual tree, the methodology presented here will also make it possible the analysis of intra-canopy variations and the accurate calculation of vegetation and water stress indices

Essays on Employment Growth, Wage Discrimination, and Marijuana Legalization

The opening chapter covers the impact of the Olympic Games on employment growth. The Olympics Games stand as the largest sporting event in the world. The Games include approximately 200 countries during the Summer Olympic Games and 90 countries competing in the Winter Games, each occurring once every four years. Potential host cities fiercely compete to host the games under the guise of economic prosperity. Event promoters claim substantial economic benefits, such as employment growth, to be had from hosting these costly games. This paper examines the impacts of the Olympic Games on employment growth rates using a synthetic control approach. Results show transitory increases in employment growth rates following a county being awarded the Olympic Games in Fulton County, GA and Salt Lake County, UT. A decrease in employment growth rate appears in Los Angeles County, CA due to being awarded the 1984 Summer Olympic Games. Results suggest that potential hosts should proceed with caution when considering hosting the Olympic Games. Chapter two investigates the prominence of wage discrimination in the National Basketball Association (NBA) using free agent signings from 2011-2017. Free agent signings allow us to better capture the determinants of players\u27 wages, a limitation of the previous NBA wage discrimination literature. Using the Oaxaca-Blinder decomposition and weighted linear regression models, we find that black athletes are paid significantly less than their counterparts. In addition, weighted quantile regressions show evidence of the presence of consumer discrimination in the league. This is observed through the result that black players with high audience visibility experience a larger racial wage gap; moreover, this gap is positively related to the share of white population of the MSA where the player is employed. In the final chapter, I explore the impact of legalization of marijuana on risky consumption of alcohol and tobacco. Utilizing BRFSS data and a differences-in-differences approach with entropy balancing, results indicate that individuals in states that introduce legal recreational marijuana experience a decrease in risky behaviors. Legal states experience a decrease in the overall use of alcohol, drinking and driving, and smokeless tobacco use. Legalization can weed out risky behaviors involving alcohol and tobacco, indicating that marijuana represents a substitute for alcohol and smokeless tobacco. No significant changes in cigarette smoking occurs following legalization

The joint effect of health shocks and eligibility for social security on labor supply

This paper investigates whether or not suffering a health shock, and becoming eligible for social security, have a joint effect on labor supply. Despite millions of people experiencing both of these events each year, no paper has focused exclusively on the joint effect that these events may have on work outcomes. This is surprising given that experiencing a health shock may impact on how a worker responds to becoming eligible for social security. With data from the Health and Retirement Study, I model weekly hours of work as a function of health shocks, social security eligibility, and their interaction. I find that this interaction leads to a 3–4 h reduction in weekly hours of work for men, but has no effect for women. The results are robust to using different work outcomes, age groups, health shock definitions, subgroups, as well as falsification and placebo tests. The results appear to be driven by men who would have had to return to work with impaired health. Policies that promote a more flexible work situation for older men may alleviate these problems in the future

The legend of Diarmuid and Grania: its history and treatment by modern writers.

Thesis (Ph.D.)--Boston UniversityThe latter half of the nineteenth century saw the beginnings in Ireland of the Celtic revival, a literary movement which sent modern Irish writers who were using the medium of English back to the ancient Gaelic literature of their country for inspiration. Historians, translators, and linguistic scholars had uncovered, in their study of this Gaelic literature, a rich mine of myth and legend which the Anglo-Irish were quick to use in literary works of their own. The old Irish literature can boast of two famous cycles. The first, called the Ulster cycle, centers around the heroes of the Red Branch who lived in north-eastern Ireland and includes the many tales of the mighty Cuchulain. The second cycle, the Fenian or Ossianic, celebrates the deeds of the popular Irish hero, Finn MacCool, and his Fenian warriors. In both cycles there are stories which modern Irish writers have found appealing enough to re-tell in English, the language which Ireland now uses. Of the Fenian tales, one of the best-known and one that is still recited as folk-lore by Gaelic-speaking peasants is the legend of Diarmuid and Grania. It differs from most of the stories in this cycle in its portrayal of Finn , not as the generous, wise , powerful leader of his men, but as a jealous , petty tyrant. The legend tells the story of Grania , the daughter of Cormac MacArt, the High King of Ireland , and Diarmuid, the handsomest man in the Fianna and nephew of Finn MacCool himself. Grania, who is betrothed to Finn, falls in love with the chivalrous Diarmuid and forces him to elope with her. They flee from the court at Tara and are pursued throughoutIreland by the jealous Finn. Eventually Finn succeeds in sending Diarmuid to his death and wins back to himself the affections of the fickle Grania.[TRUNCATED] The manner in which an author re-tells an old story and gives it creative treatment of his own is always of interest to t he student of literature. The several authors who were attracted to the legend of Diarmvuid and Grania have all handled the old story differently and with varying degrees of success.(Brief mention has been made in this study of the allusive and symbolical references to the legend in James Joyce's Finnegans Wake.) Although the central line of action is the same, the characterizations, the selection of episodes from the original versions, and the actual method of unfolding the narrative all differ in these modern re-tellings. That so many writers found the old story appealing enough to warrant their giving it literary treatment of their own points to the human appeal and enduring interest of this old Celtic love story

The Public Choice of Public Stadium Financing: Evidence from San Diego Referenda

Abstract: Local politicians and team owners frequently argue that the public financing of stadiums is important for local economic development. The sports economics literature, however, has largely found that new professional sport facilities do not generate any new net economic activity. We provide context to this literature by exploring the public choice in the public financing of stadiums. In 2016, San Diego had two ballot measures related to the San Diego Chargers. Measure C would allow officials to raise hotel taxes to pay for a new downtown stadium for the Chargers. Measure D would also raise hotel taxes, but explicitly prevented any money being spent on the Chargers. Both measures failed to receive 50% of the votes cast. We find that zip codes with a higher voter turnout were more likely to vote against both measures, highlighting the importance of the timing of referenda in limiting the ability of clearly defined groups, such as Chargers fans, to have a large influence on the voting outcome. Meanwhile, areas with more Trump voters were more likely to support higher taxes for the purpose of building the Chargers a new stadium

The Effect of Superstar Players on Game Attendance: Evidence from the NBA

Economic models predict that “superstar” players generate externalities that increase attendance and other revenue sources beyond their individual contributions to team success. We investigate the effect of superstar players on individual game attendance at National Basketball Association games from 1981/82 through 2013/14. Regression models control for censoring due to sellouts, quality of teams, unobservable team/season heterogeneity, and expected game out-comes. The results show higher home and away attendance associated with superstar players. Michael Jordan generated the largest superstar attendance externality, generating an additional 5,021/5,631 fans at home/away games

Do National Basketball Association Players Need Higher Salaries to Play in High Tax States? Evidence from Free Agents

This paper investigates the impact of taxes on the salaries received by National Basketball Association free agents from 2010-2014. High state income tax rates affect the after-tax income received by players from their team as well as on any ancillary income. Using data on 576 free agents, we find statistically significant evidence that free agents signing in high tax states receive higher salaries, ceteris paribus. Our results suggest that a one-unit increase in the average tax rate experienced by a free agent in a state leads to free agent salaries being over $60,000 higher

The Effect of Superstar Players on Game Attendance: Evidence from the NBA

Economic models predict that \superstar players generate externalities that increase attendance and other revenue sources beyond their individual contributions to team success. We investigate the effect of superstar players on individual game attendance at National Basketball Association games from 1981/82 through 2013/14. Regression models control for censoring due to sellouts, quality of teams, unobservable team/season heterogeneity, and expected game outcomes. The results show higher home and away attendance associated with superstar players. Michael Jordan generated the largest superstar attendance externality, generating an additional 5,021/5,631 fans at home/away games

Supply of Primary Care Providers and Appointment Availability for Philadelphia\u27s Medicaid Population

This brief analyzes the supply of primary care providers serving the Medicaid population in Philadelphia, and the geographic variability of this measure across the city. It also examines important measures of access – appointment availability and wait time for an initial appointment – that highlight challenges faced by Medicaid patients