Application of satellite communication to hydrographic data processing

The Hydrographic Department and the Information Systems Department at the Naval Oceanographic Office (NAVOCEANO) successfully transmitted coastal area sounding and position data collected by USNS John McDonnell, a recently built survey vessel, from the Gulf of Mexico to NAVOCEANO at Stennis Space Center, Mississippi.

Two external modems were used to modulate and demodulate the data that were received from a MICROVAX 3400 aboard USNS McDonnell and sent to the Intergraph Interactive Workstation at NAVOCEANO via the MARISTAT communication satellite. The Kermit file transfer protocol was used to bridge the different operating environments between input/output (I/O) devices and central processors.

Office processors were able to evaluate the data prior to the departure of the survey platform from the area. From this data, smooth sheets‐were produced. Equipment upgrades and more efficient use of satellite availability within the entire INMARSAT system should allow near‐real‐time editing and validation of field hydro‐graphic data.     

A new method for estimating high-frequency radar error using data from Central San Francisco Bay

This study offers a new method for estimating High-Frequency (HF) radar surface current velocity error in data comparisons with other types of instrumentation. A new method is needed in order to remove the zero-mean random spatial and temporal fluctuations present in surface-current measurements from all sensors. Conventional methods for calculating radar error when comparing with another instrument have included their root mean square differences and scatter plots that provide correlation coefficient and slope/intercept of the regression line. It seems that a meaningful estimate of radar error should attempt to remove both sensors’ zero mean random fluctuations, inasmuch as possible. We offer and compare a method that does this. The method was tested on data collected in the Central San Francisco Bay, where GPS surface-drifter deployments were conducted within the coverage of four 42 MHz radars over six days in October of 2008. Drifters were continuously deployed in these areas over the sampling days, providing 525 usable drifter measurements. Drifter and radar measurements were averaged into thirty-minute time bins. The three-day long-term averages from the sampling areas were then subtracted from the thirtyminute averages to remove biases associated with comparisons done with short, disjoint time-sample periods. These were then used to develop methods that give radar error or bias after the random fluctuations have been removed. Results for error estimates in this study are commensurate with others where random fluctuations have been filtered, suggesting they are valid. The estimated error for the radars in the SF Bay is low, ranging from ?7.57 cm/s to 0.59 cm/s.     

The university of New South Wales automated patrol telescope

The Automated Patrol Telescope is a wide-field CCD imaging telescope of novel design. The telescope is a converted Baker-Nunn satellite tracking camera that has undergone extensive modification to its optical, mechanical and electronic systems. Telescope operation is entirely under computer control, and the instrument is to be used for a variety of astronomical survey and monitoring projects.     

Generating random numbers in the field

A pseudo-random number generator which is easy to remember and uses the very simple sequences 321 and 123 can be readily implemented on any available hand calculator. The generator is given by the recursive relation: R_i=321 × R_i–1+123, and is initiated using any 5-digit number for R_i–1 and saving the rightmost 5 digits of R_i for the next R_i–1;the two leftmost digits of R_i then yield an acceptable random number between 00 and 99. Alternately, a much better generator is given which can be jotted down in a notebook or taped to the back of your calculator.     

A brief description of the fundamental difficulties in passive ranging

The use of passive sensors to estimate range and bearing to an acoustic source is investigated. The variance of the estimators is shown to depend on the number of sensors, integration time, signal-to-noise ratio, and more significantly, on the available array length. The variances for four different array configurations are discussed.     

Battles from below: a literature of oppression

Janet Frame is a New Zealand writer who was institutionalized for nearly nine years in mental illness hospitals. Her experiences have been fictionalized in her novel, Faces in the Water, and it is these novelistic representations of the asylum that we explore in this paper. As Frame has suggested in her second volume of autobiography, An Angel at My Table, there is a personal, geographic and linguistic exclusiveness to the asylum in that the patients are stripped of their identity and forced to conform. How these themes are developed in Faces in the Water will be the focus of this paper.     

On the use of instar information in the analysis of subfossil chironomid data

Head capsules of chironomids of the genera Chironomus, Glyptotendipes and Microtendipes in two cores from Lough Neagh, Northern Ireland, were identified to instar. The proportions of 3rd and 4th instars did not stay constant throughout the lengths of the cores and it is possible there was differential preservation of the instars. Plotting diagrams using only one instar could give misleading information about the occurrence of a genus, while plotting total number of head capsules may result in individuals being counted twice. Counting the most numerous taxon at each level in the sediment avoids the latter problem while retaining maximum information about the fauna. Non-metric Multi-Dimensional Scaling ordination diagrams calculated using the different methods illustrate the similarity of plot obtained.     

Size and stress gradient effects on fracture around cavities

Summary The effect of hole size on fracture initiation around cavities in rock is examined through physical model tests on Tyndall limestone. Twenty five models, employing nine different hole sizes, ranging from 3.2 to 62 mm in diameter were tested in uniaxial compression. Strain gauges placed both on the face of the model block and inside the cylindrical cavity were used to record the state of fracture.Fracture initiation data for primary, remote and sidewall fractures were determined using the stress-strain curves from the respective strain gauge locations. For all three fracture types, the initiation stress decreases with increasing hole size and appears to approach a horizontal asymptote for large cavity sizes. The fracture mechanics formulations and the stress averaging method give the best fit to the primary fracture initiation except for very small cavity sizes. The stress averaging method also provides a very good fit to the sidewall fracture initiation data.     

Moving salt sills and hydrocarbon maturity

Salt sills have been observed in the Gulf Coast. The contrast in the thermal conductivity between salt and detrital sediments means that a salt sill focuses heat around its leading edge, resulting in the devlopment of an anomalous temperature pattern in the vicinity of the salt sill. The consequent anomaly in thermal maturity pattern for hydrocarbons is related to four parameters: the salt sill thickness; the subsurface depth of the sill; the inclination of the sill; and the salt speed through the sediments. The excess maturity in the vicinity of the salt sill is shown to be dominantly dependent on the velocity of the salt sill. The positional influence of the hydrocarbon maturity relative to the salt is also examined and it is shown that the alteration of sedimentary burial paths by the inserted salt also causes a thermal anomaly. Both thermal focusing of heat by salt and sediment burial to a different thermal regime caused by passage of inserted salt produce thermal maturity effects comparable in magnitude, and neither may be ignored.The work here was supported by the Industrial Associates of the Basin Analysis Group at the University of South Carolina.