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At least 37 records · Page 2Linked to original sources
USGS2007

Radiometric recalibration procedure for Landsat-5 Thematic Mapper data

The Landsat-5 (L5) satellite was launched on March 01, 1984, with a design life of three years. Incredibly, the L5 Thematic Mapper (TM) has collected data for 23 years. Over this time, the detectors have aged, and its radiometric characteristics have changed since launch. The calibration procedures and parameters have also changed with time. Revised radiometric calibrations have improved the radiometric accuracy of recently processed data; however, users with data that were processed prior to the calibration update do not benefit from the revisions. A procedure has been developed to give users the ability to recalibrate their existing Level 1 (Ll) products without having to purchase reprocessed data from the U.S. Geological Survey (USGS). The accuracy of the recalibration is dependent on the knowledge of the prior calibration applied to the data. The “Work Order” File, included with standard National Land Archive Production System (NLAPS) data products, gives parameters that define the applied calibration. These are the Internal Calibrator (IC) calibration parameters or the default prelaunch calibration, if there were problems with the IC calibration. This paper details the recalibration procedure for data processed using IC, in which users have the Work Order file.

Conference Paper↗
USGS2006

Hydratools manual version 1.0, documentation for a MATLAB ® -based post-processing package for the Sontek Hydra

The Sediment Transport Instrumentation Group (STG) at the U.S. Geological Survey (USGS) Woods Hole Science Center has a long-standing comitment to providing scientists with high quality oceanographic data. To meet this commitment, STG personnel are vigilant in checking data as well as hardware for signs of instrument malfunction. STG data sets are accompanied by processing histories to detail data processing procedures that may have modified the natural data signal while removing noise from the data. The history also allows the data to be reprocessed in the ligth of new insight into instrument function and moored conditions. This toolbox was compiled to meet these data quality commitments for data generated by Sontek Hydra systems using both ADV and PCADP probes. In the mid 1900's, the USGS Coastal and Marine Program began frequent deployments of Sontek Hydra systems in support of projects in estuaries, coastal, and continental shelf regions nationwide. Hydra data sets are large and complex in structure, and existing processing and editing tools consisted of fragments of MATLAB code written by USGS scientists to satisfy personal research needs. This code did not meet STG quality control criteria. This toolbox permits engineers and scientists to monitor data quality by: 1. processing data with interactive critical review; 2. preserving data quality indicators; 3. preserving minimally processed and partially processed versions of data sets. STG usually deploys ADV and PCADP probes configured as downward looking, mounted on bottom tripods, with the objective of measuring high-resolution near-bed currents. The velocity profiles are recorded with minimal internal data processing. Also recorded are parameters such as temperature, conductivity, optical backscatter, light transmission, and high frequency pressure. Sampling consists of high-frequency bursts(1–10 Hz) bursts of long duration (5–30 minutes) at regular and recurring intervals for a duration of 1 to 6 months. The result is very large data files, often 500 MB per Hydra, per deployment, in Sontek's compressed binary format. This section introduces the Hydratools toolbox and provides information about the history of the system's development. The USGS philosophy regarding data quality is discussed to provide an understating of the motivation for creating the system. General information about the following topics will also be discussed: hardware and software required for the system, basic processing steps, limitations of program usage, and features that are unique to the programs.

Open-File Report↗
USGS2021

System characterization report on the Gaofen-1

Executive Summary This report addresses system characterization of Gaofen-1 and is part of a series of system characterization reports produced and delivered by the U.S. Geological Survey Earth Resources Observation and Science Cal/Val Center of Excellence in 2020. These reports present the detail methodology and procedures for characterization; present technical and operational information about the specific sensing system being evaluated; and provide a summary of test measurements, data retention practices, data analysis results, and conclusions. Gaofen represents a series of Chinese high-resolution Earth observation satellites. More than 12 satellites have been launched in the Gaofen series, beginning with Gaofen-1 in 2013. Satellites within the series have varying infrared, radar, and optical imaging capabilities. The primary goal for the satellite is to provide near real-time observations for climate change monitoring, geographical mapping, precision agriculture support, environmental and resource surveying, and disaster prevention. More information on Chinese satellites and sensors is available within the “2020 Joint Agency Commercial Imagery Evaluation—Remote Sensing Satellite Compendium” and at http://www.cnsageo.com/#/detailIndex?secondIndex=2&id=3&code=8 . The Earth Resources Observation and Science Cal/Val Center of Excellence System Characterization team completed data analyses to characterize the geometric (interior and exterior), radiometric, and spatial performances. Results of these analyses indicate that Gaofen-1 has an interior geometric performance of −0.48 meter (m) (−0.03 pixel) northing and 0.42 m (0.03 pixel) easting offset for band 1, −0.99 m (−0.06 pixel) northing and −0.38 m (−0.02 pixel) easting offset for band 2, −0.45 m (−0.03) northing and 0.83 m (0.05 pixel) easting offset for band 3, −3.20 m (−0.20 pixel) northing and 1.44 m (0.09 pixel) easting offset for band 4 in band-to-band registration. Similarly, Gaofen-1 has an exterior geometric performance of 7.50 m (0.48 pixel) easting and 109.50 m (7.30 pixels) northing offset in comparison to the Landsat 8 Operational Land Imager; a radiometric performance in the range of −0.014 to 0.149 (absolute reflective difference); and a spatial performance in the range of 1.1 to 2.0 pixels at full width at half maximum, with a modulation transfer function at a Nyquist frequency in the range of 0.040 to 0.250.

Open-File Report↗
USGS1999

Workplan for U.S. Geological Survey hydrologic data-collection and support activities on Fort Wainwright, Alaska, 1994-97

The U.S. Army Alaska is responsible for environmental activities on Fort Wainwright near Fairbanks, Alaska. In order to better meet the needs of environmental investigations, the Army requires geohydrologic information about the Fort Wainwright area. Since 1994, the U.S. Geological Survey has been working in cooperation with the U.S. Army Alaska and the U.S. Army Corps of Engineers to investigate the geohydrology of the Fort Wainwright area. The primary objectives of the study are to collect basic ground-water and surface-water data and to support ongoing environmental investigations by other agencies. This report is the workplan describing the technical methods used by the USGS to meet these objectives. It includes details on field procedures, data collection, and analyses of water samples.

Open-File Report↗
USGS1968

General procedure for gaging streams

This chapter briefly describes the objectives and procedures used in obtaining streamflow records. It is considered an introduction to other chapters on surface-water techniques which treat individual procedures in greater detail.

Techniques of Water-Resources Investigations↗
USGS2000

Altitude, depth, and thickness of the Galena-Platteville Bedrock Unit in the subcrop area of Illinois and Wisconsin

The Galena-Platteville bedrock unit is a carbonate deposit of Ordovician age, composed of the Galena and Platteville Groups in Illinois and the Sinnippee Group in Wisconsin. It is the uppermost bedrock unit (subcrop) in most of northern Illinois and southern and eastern Wisconsin. The subcrop area is shaded in figure 1 of sheet 1 (Batten and others, 1997). The unit is predominately dolomite, with limestone in some areas, and has a weathered surface. Across the subcrop area, the hydrologic characteristics of the bedrock unit vary substantially. The bedrock unit may be either a confining unit or an aquifer. In areas where the Galena-Platteville bedrock unit is an aquifer, the unit is a dependable source of water for many private wells and some municipal-water-supply systems. Ground water in the Galena-Platteville bedrock aquifer is susceptible to contamination because the bedrock unit is near land surface in much of the study area, and the fractures in the unit allow rapid movement of water providing limited capacity to attenuate contaminants. The subcrop (study) area covers approximately 7,850 square miles in northern Illinois and Wisconsin. In the study area, volatile organic compounds and other contaminants have been detected in the aquifer at various sites (Mills, 1993; Kay and others, 1994). Many sources of contaminants, including landfills and industrial facilities, are known or suspected. In order to determine the possible effects of contamination on the ground-water supply, an understanding of the regional hydrogeologic framework of the Galena-Platteville bedrock unit is needed. Published and unpublished map and point data describing the geologic properties of the Galena-Platteville bedrock unit are available from many sources. The U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (USEPA), has selected and compiled a large portion of the available data to create computer data bases and maps. The objective of this effort is to compile and publish these data in a series of reports (U.S. Geological Survey Water-Resources Investigations Reports (WRIR) 974054-A, WRIR 97-4054-B, WRIR 97-4054-C). This is the third in that series of reports. The report describes the altitude, thickness, and depth from land surface of the subcrop area of the Galena-Platteville bedrock unit. The report series will enable investigators involved in site-specific studies within the subcrop area to understand the regional geologic framework of the unit and to find additional reference sources. This report consists of four sheets that show the altitude (sheet 1), depth from land surface (sheet 2), total thickness (sheet 3), and location of altitude data (sheet 4) of the lithologic units that constitute the Galena-Platteville bedrock unit within the subcrop area. The sheets also show major known geologic features within the Galena-Platteville study area in Illinois and Wisconsin. A geographic information system (GIS) was used to generate data layers (coverages) from point data and from published and unpublished contour maps at various scales and detail. Standard GIS procedures were used to change the coverages into the maps shown on the sheets presented in this report. A list of references for the data used to prepare the maps is provided.

Illinois, Wisconsin↗
USGS2026

The surface elevation table and marker horizon technique: A protocol for measuring wetland elevation dynamics, narrative (Version 2.0)

The National Park Service (NPS), in response to the growing evidence and awareness of the effects of climate change on federal lands, determined that monitoring wetland elevation change is a top priority in North Atlantic Coastal parks (Stevens et al. 2010). As a result, the NPS Northeast Coastal and Barrier Network (NCBN) in collaboration with colleagues from the U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA) have developed a protocol for monitoring wetland elevation change and other processes important for determining the viability of wetland communities. Although focused on North Atlantic Coastal parks, this document is applicable to all coastal and inland wetland regions. Wetlands exist within a narrow range of elevation that is influenced by local hydrologic conditions. For tidally influenced coastal wetlands, local hydrologic conditions may be changing as sea levels continue to rise. As sea level rises, coastal wetland systems may either a) build elevation to maintain favorable hydrologic conditions for their survival or b) become increasingly inundated beyond their physiological tolerance resulting in an eventual conversion to open water. A better understanding of these processes will help to determine the present and future viability of coastal wetlands managed by the NPS and can help address measures to ensure these communities exist into the future. This protocol provides the reader with instructions and guidelines on designing a monitoring plan or study to: Quantify elevation change in wetlands with the Surface Elevation Table (SET); understand the processes that influence elevation change, including vertical accretion (SET and Marker Horizon methods); survey the wetland surface and SET mark to a common reference datum to allow for comparing sample stations to each other and to local tidal datums; survey the SET mark to monitor its relative stability; and establish water level equipment to characterize the hydrology and tidal datums for a particular wetland site or sites. The protocol is divided into two documents: The narrative (this document) presents an overview of all aspects of monitoring wetland elevation dynamics, and a document of Standard Operating Procedures (SOPs) with detailed instructions on the design, installation, data collection, and data management in support of monitoring changes in wetland elevation.

Science Report↗
USGS2026

Thermal detectability of subsurface water ice on Mars: A comparative analysis for the Subsurface Water Ice Mapping (SWIM) Project

We have developed a new global map of shallow ground ice distribution, SWIM23, based on Mars Global Surveyor Thermal Emission Spectrometer data and made systematic comparisons between this new map and two similar, previously developed data products. We have explored the origin of differences between the three ice maps by detailing technical and procedural differences in their development, by making global pixel-by-pixel comparisons, and by carrying out a series of one-dimensional thermal simulations to explore fundamental physical limitations of thermal ice-detection techniques. These efforts and the production of a composite thermal ice-consistency map supported integration of multiple geophysical data products relevant to ice detection in the upper meter of the Martian regolith into the larger Mars Subsurface Water Ice Mapping project. Our work also highlights fundamental physical limitations to thermal ice detection as a technique, particularly the rapid fall-off in ice detection sensitivity at depths >30 cm, which produces maximum uncertainty in the presence and depth of ice within regions preferred for potential human landing sites. A future Mars orbiter mission designed to detect ice and support crewed landing site selection in the midlatitude region should give payload priority to an instrument capable of probing the 1–5 m depth range (i.e., a high-frequency radar), over a next-generation thermal spectrometer, which is unlikely to offer clarity on ice table depths or lateral continuity of the ice table in the locations of highest interest.

Planetary Science Journal↗
USGS2001

Guidelines for the field evaluation of desert tortoise health and disease

Field evaluation of free-ranging wildlife requires the systematic documentation of a variety of environmental conditions and individual parameters of health and disease, particularly in the case of rare or endangered species. In addition, defined criteria are needed for the humane salvage of ill or dying animals. The purpose of this paper is to describe, in detail, the preparation, procedures, and protocols we developed and tested for the field evaluation of wild desert tortoises ( Gopherus agassizii ). These guidelines describe: preparations for the field, including developing familiarity with tortoise behavior and ecology, and preparation of standardized data sheets; journal notes to document background data on weather conditions, temperature, rainfall, locality, and historic and recent human activities; procedures to prevent the spread of disease and parasites; data sheets for live tortoises to record tortoise identification, location, sex, body measurements and activity; health profile forms for documenting and grading physical abnormalities of tortoise posture and movements, general condition (e.g., lethargy, cachexia), external parasites, and clinical abnormalities associated with shell and upper respiratory diseases; permanent photographic records for the retrospective analysis of progression and regression of upper respiratory and eye diseases, analysis of shell lesions and evaluation of growth and age; and indications and methods for salvaging ill or dying tortoises for necropsy evaluation. These guidelines, tested on 5,000 to 20,000 tortoises over a 10 to 27 yr period, were designed to maximize acquisition of data for demographic, ecological, health and disease research projects; to reduce handling and stress of individual animals; to avoid spread of infectious disease; to promote high quality and consistent data sets; and to reduce the duration and number of field trips. The field methods are adapted for desert tortoise life cycle, behavior, anatomy, physiology, and pertinent disease; however the model is applicable to other species of reptiles. Comprehensive databases of clinical signs of disease and health are crucial to research endeavors and essential to decisions on captive release, epidemiology of disease, translocation of wild tortoises, breeding programs, and euthanasia.

Journal of Wildlife Diseases↗
USGS1958

Operator's manual on the visual-accumulation tube method for sedimentation analysis of sands

The visual-tube method for sedimentation analysis of sands was developed as a part of the general investigation titled "A Study of Methods Used in Measurement and Analysis of Sediment Loads in Streams." The method is one answer to the need for a simple, rapid, and inexpensive means of determining the sedimentation-size frequency analysis of sand samples containing particles less than one millimeter in size. For analysis of coarser sands see the Appendix, Section 13, Report No. 11 "The Development and Calibration of the Visual-Accumulation-Tube" is available for those who have further interest in this analysis. The personnel who will be operating these units may have little or no previous knowledge of either the principles involved or the details of opera.ting procedure. This manual is intended as an aid to them in setting up the apparatus, learning the analytical procedure, interpreting the results, and understanding the primary principles encountered.

Report↗
USGS2014

Water quality monitoring protocol for wadeable streams and rivers in the Northern Great Plains Network

Preserving the national parks unimpaired for the enjoyment of future generations is a fundamental purpose of the National Park Service (NPS). To address growing concerns regarding the overall physical, chemical, and biological elements and processes of park ecosystems, the NPS implemented science-based management through “Vital Signs” monitoring in 270 national parks (NPS 2007). The Northern Great Plains Network (NGPN) is among the 32 National Park Service Networks participating in this monitoring effort. The NGPN will develop protocols over the next several years to determine the overall health or condition of resources within 13 parks located in Nebraska, North Dakota, South Dakota, and Wyoming. The NGPN identified water resources as a Vital Sign to monitor because water quality and quantity are important aspects of ecological processes that operate across multiple temporal and spatial scales. In the semi-arid region of the Northern Great Plains, surface-water resources within the NGPN are ecologically important. The 13 parks within the NGPN are diverse and vary greatly in size, visitation, and water resources. For example, the measured surface area of the Badlands National Park is about 243,000 acres, which represents nearly one-half of the combined acreage of all 13 NGPN park units; however, water resources within the park are scarce and the majority of streams are intermittent. The Badlands National Park annually hosts nearly 860,000 visitors. Mount Rushmore National Memorial also has limited water resources but hosts nearly 3 million visitors per year within its 1,278 acres. The Missouri National Recreational River contains the greatest portion of waterbodies within the NGPN, consisting of 139 rivers and streams within an areal extent of about 69,000 acres. Although water resources and acreage of the NGPN parks are varied, unifying factors among the parks include the relatively low population density within the Great Plains area and the strong emphasis on agrarian land use throughout the region. To address the diverse water quality concerns, NGPN received input from park staff and conducted pilot studies in 2009 and 2010. These factors, in combination with the NGPN budget allocations, resulted in development of the NGPN’s water quality monitoring protocol. This protocol will provide a context to aid park resource managers in their day-to-day decisions and allow the assessment of the status (current conditions) and trends (directional changes across time) of streams/rivers within selected NGPN parks. Data collected from integrating water resource monitoring, in combination with the inventory of additional Vital Signs, can be used to assess resources and to aid in sound managerial decisions by the NGPN parks. As recommended by Oakley et al. (2003), this protocol provides a narrative and the rationale for selection of streams and rivers within the NGPN that will be measured for water quality, including dissolved oxygen, pH, specific conductivity, and temperature. Standard operating procedures (SOPs) that detail the steps to collect, manage, and disseminate the NGPN water quality data are in an accompanying document. The sampling design documented in this protocol may be updated as monitoring information is collected and interpreted, and as refinement of methodologies develop through time. In addition, evaluation of data and refinement of the program may necessitate potential changes of program objectives. Changes to the NGPN water quality protocols and SOPs will be carefully documented in a revision history log.

Colorado, Montana, Nebraska, North Dakota, South D↗
USGS2023

Geospatial standard operating procedures of the Chesapeake Bay Program

Introduction The Chesapeake Bay Program (CBP) has operated a geographic information system (GIS) program since the early 1990s to address the established and growing need for and use of geospatial data, maps, and analysis within the CBP Partnership. This report is intended to detail the standard operating procedures of the CBP GIS program and address the quality assurance, quality control, and other technical activities that CBP will implement to ensure the commitment of the CBP GIS Team to performance standards (U.S. Environmental Protection Agency, 2003). The report is intended as an update to the 2011 Quality Assurance Project Plan (QAPP). For specialized tasks or analytical projects beyond the scope of this QAPP, a separate specialized QAPP with details on quality control, assurance procedures, and the geospatial methods associated with all aspects of the project may be required.

Open-File Report↗
USGS1994

Measuring and monitoring biological diversity: Standard methods for amphibians

Measuring and Monitoring Biological Diversity is the first book to provide comprehensive coverage of standard methods for biodiversity sampling of amphibians, with information on analyzing and using data that will interest biologists in general. In this manual, nearly fifty herpetologists recommend ten standard sampling procedures for measuring and monitoring amphibian and many other populations. The contributors discuss each procedure, along with the circumstances for its appropriate use. In addition, they provide a detailed protocol for each procedure's implementation, a list of necessary equipment and personnel, and suggestions for analyzing the data. The data obtained using these standard methods are comparable across sites and through time and, as a result, are extremely useful for making decisions about habitat protection, sustained use, and restoration—decisions that are particularly relevant for threatened amphibian populations.

Book↗
USGS2006

A Procedure for the supercritical fluid extraction of coal samples, with subsequent analysis of extracted hydrocarbons

Introduction: This report provides a detailed, step-by-step procedure for conducting extractions with supercritical carbon dioxide (CO2) using the ISCO SFX220 supercritical fluid extraction system. Protocols for the subsequent separation and analysis of extracted hydrocarbons are also included in this report. These procedures were developed under the auspices of the project 'Assessment of Geologic Reservoirs for Carbon Dioxide Sequestration' (see http://pubs.usgs.gov/fs/fs026-03/fs026-03.pdf) to investigate possible environmental ramifications associated with CO2 storage (sequestration) in geologic reservoirs, such as deep (~1 km below land surface) coal beds. Supercritical CO2 has been used previously to extract contaminants from geologic matrices. Pressure-temperature conditions within deep coal beds may render CO2 supercritical. In this context, the ability of supercritical CO2 to extract contaminants from geologic materials may serve to mobilize noxious compounds from coal, possibly complicating storage efforts. There currently exists little information on the physicochemical interactions between supercritical CO2 and coal in this setting. The procedures described herein were developed to improve the understanding of these interactions and provide insight into the fate of CO2 and contaminants during simulated CO2 injections.

Open-File Report↗
USGS1983

Computation of continuous records of streamflow

Records of continuous streamflow, published in the U.S. Geological Survey annual Water Data Reports for the States and territories, are computed from field data, mainly discharge measurements and recorder charts or tapes. This manual describes the computation procedures used and some details of related field operations. It was compiled mostly from unpublished Water Resource Division district manuals edited and supplemented to emphasize digital-recorder and associated computer use. Methods used primarily for graphic-recorder gaging stations and non-recording gages are also included. Reference is made to other publications for some of the more specialized or unusually complex procedures.

Techniques of Water-Resources Investigations↗
USGS2010

A procedure for radiometric recalibration of Landsat 5 TM reflective-band data

From the Landsat program's inception in 1972 to the present, the Earth science user community has been benefiting from a historical record of remotely sensed data. The multispectral data from the Landsat 5 (L5) Thematic Mapper (TM) sensor provide the backbone for this extensive archive. Historically, the radiometric calibration procedure for the L5 TM imagery used the detectors' response to the internal calibrator (IC) on a scene-by-scene basis to determine the gain and offset for each detector. The IC system degraded with time, causing radiometric calibration errors up to 20%. In May 2003, the L5 TM data processed and distributed by the U.S. Geological Survey (USGS) Earth Resources Observation and Science Center through the National Landsat Archive Production System (NLAPS) were updated to use a lifetime lookup-table (LUT) gain model to radiometrically calibrate TM data instead of using scene-specific IC gains. Further modification of the gain model was performed in 2007. The L5 TM data processed using IC prior to the calibration update do not benefit from the recent calibration revisions. A procedure has been developed to give users the ability to recalibrate their existing level-1 products. The best recalibration results are obtained if the work-order report that was included in the original standard data product delivery is available. However, if users do not have the original work-order report, the IC trends can be used for recalibration. The IC trends were generated using the radiometric gain trends recorded in the NLAPS database. This paper provides the details of the recalibration procedure for the following: 1) data processed using IC where users have the work-order file; 2) data processed using IC where users do not have the work-order file; 3) data processed using prelaunch calibration parameters; and 4) data processed using the previous version of the LUT (e.g., LUT03) that was released before April 2, 2007.

IEEE Transactions on Geoscience and Remote Sensing↗
USGS1999

Professional conduct of scientists during volcanic crises

Stress during volcanic crises is high, and any friction between scientists can distract seriously from both humanitarian and scientific effort. Friction can arise, for example, if team members do not share all of their data, if differences in scientific interpretation erupt into public controversy, or if one scientist begins work on a prime research topic while a colleague with longer-standing investment is still busy with public safety work. Some problems arise within existing scientific teams; others are brought on by visiting scientists. Friction can also arise between volcanologists and public officials. Two general measures may avert or reduce friction: (a) National volcanologic surveys and other scientific groups that advise civil authorities in times of volcanic crisis should prepare, in advance of crises, a written plan that details crisis team policies, procedures, leadership and other roles of team members, and other matters pertinent to crisis conduct. A copy of this plan should be given to all current and prospective team members. (b) Each participant in a crisis team should examine his or her own actions and contribution to the crisis effort. A personal checklist is provided to aid this examination. Questions fall generally in two categories: Are my presence and actions for the public good? Are my words and actions collegial, i.e., courteous, respectful, and fair? Numerous specific solutions to common crisis problems are also offered. Among these suggestions are: (a) choose scientific team leaders primarily for their leadership skills; (b) speak publicly with a single scientific voice, especially when forecasts, warnings, or scientific disagreements are involved; (c) if you are a would-be visitor, inquire from the primary scientific team whether your help would be welcomed, and, in general, proceed only if the reply is genuinely positive; (d) in publications, personnel evaluations, and funding, reward rather than discourage teamwork. Models are available from the fields of particle physics and human genetics, among others.

Bulletin of Volcanology↗
USGS1989

Population trends of North American shorebirds based on the International Shorebird Survey

Shorebirds Charadrii are prime candidates for population decline because of their dependence on wetlands that are being lost at a rapid pace. Thirty-six of the 49 species of shorebirds that breed in North America spend most of the year in Latin America. Because populations of most species breed and winter at remote sites, it may be most feasible to monitor their numbers at migration stopovers. In this study, we used statistical trend analysis methods, developed for the North America Breeding Bird Survey, to analyze data on shorebird populations during southbound migration in the United States. Survey data were collected by volunteers in the International Shorebird Survey (ISS). The analyses indicate that whimbrels Numenius phaeopus , short-billed dowitchers Limnodromus griseus , and sanderlings Calidris alba have undergone statistically significant declines. Methodological concerns over both the ISS and the trend analysis procedures are discussed in detail and biological interpretations of the results are suggested.

Biological Conservation↗