Latitude Values Research Articles

Three‐Dimensional Adjustment Computations Model

A three‐dimensional (3‐D) model based on the connectivity of astronomic and geodetic coordinate systems is developed from basic principles. It provides for simultaneous adjustment of most conventional types of terrestrial surveying observations. Observation equations express observed quantities in 3‐D space and are referenced to the local vertical at the point of observation. Classical reductions of observations to the reference ellipsoid prior to adjustment are not necessary. A least squares solution yields adjusted geodetic rectangular coordinates from which geodetic latitude, longitude and height values may be found. For most networks, astronomic coordinate values will also be obtained, but these values are probably reliable only if astronomic observations are included in the survey. The 3‐D model should provide a sound theoretical basis for development of a fully‐integrated adjustment model that includes conventional, photogrammetric, inertial, satellite and other surveying system observations. Additional research is desirable to evaluate the 3‐D method's full potential for applications such as local densification and project control surveys.

Miocene equatorial and southwest Pacific paleoceanography from stable isotope evidence

Stable isotope results from seven Miocene Deep Sea Drilling Projects in the equatorial and southwest Pacific Ocean, previously correlated using carbon isotope stratigraphy, have been examined, discussed, and interpreted in terms of the development of the Miocene Pacific Ocean. The most obvious features of the benthonic foraminiferal stable isotopic records are a major increase inδ 18O(∼1.0‰) during the Middle Miocene, a series of long-term oscillations (2–3 My) of amplitude 0.5–0.75‰ and a decrease inδ 13C values (0.5–;1.0‰) during the latest Miocene. Planktonic foraminiferalδ 18O records show different trends for high and low latitude regions. In the equatorial Pacific, planktonicδ 18O values actually decrease during the Miocene whereas in the higher southern latitudes planktonicδ 18O values become more positive in response to cooling surface waters. Planktonicδ 13C records show opposite trends toδ 18O with the high latitude values becoming more negative relative to the tropical regions. The development of the Miocene Pacific Ocean in terms of its vertical and horizontal thermal structure and isotopic composition is well illustrated by examining changes in the isotopic difference between planktonic and benthonic foraminifera.Δδ 18O B-P (Benthonic-Planktonic) is a measure of the thermal structure of the water column.Δδ 18O P H-P L (high latitude-low latitude) planktonic values is a measure of the latitudinal temperature gradient.Δδ 13C B-P is an indirect measure of nutrient concentrations in the water column, andΔδ 13C P H-P L measures differences in surface-water nutrient concentrations between high and low latitude. Δδ 18O B-P increases during the Miocene with the greatest increase occurring in the Middel Miocene at about 14 Ma. By the latest Miocene the isotopic gradient at Site 289 in the equatorial Pacific approaches the present-day isotopic gradient (about 4–5‰). An increase inΔδ 18O P H-P L during the Miocene suggests that the latitudinal temperature gradient increased by about 6°C to a value of 12°C in the latest Miocene between Sites 289 (Equator) and 281 (subantarctic). Δδ 13C B-P and Δδ 13C P H-P L values are relatively constant through the Early Miocene but begin to increase during the Middle Miocene. Bottom-waterδ 13C values respond similarly at all sites, but surface-waterδ 13C values exhibit different trends because higher latitude values begin to decrease. This decrease perhaps suggests that phosphate concentrations may have increased due to increased upwelling as the circum-Antarctic circulation system evolved its present day characteristics. The isotopic data compiled in this paper suggest that the southwest Pacific was responding uniformly to some global or at least Pacific-wide control during the Early Miocene. In the Middle Miocene the response became more complex as the low and high latitudes began to show independent trends. The changes in the thermal (vertical and latitudinal) structure probably occurred in respons to the build-up of the East Antarctic ice-sheet, intensification of bottom-water circulation and an increase in zonal circulation in surface waters in the southern hemisphere. The changes inδ 13C (vertical and latitudinal) gradients are due to some complex interaction of sea-level, continental hypsometry, climate, and biological processes coupled with oceanic circulation changes. A strong correlation between estimated sea-level changes andδ 13C values suggests that transgressions and regressions play a critical role in controlling the flux of oxidized organic carbon enriched in 12C, from the continental shelves and epicontinental seas to the open ocean.

Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2O, NO, NO2, and HNO3

The importance Of NOx compounds to stratospheric chemistry has been clearly established. We report below on a program to measure latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2, and HNO3 amounts. Through the use of airborne Fourier transform absorption spectroscopy, we determine simultaneously column amounts above 12 km of the four molecules listed above. Nitrous oxide (N2O) is found to have a fairly uniform distribution with latitude and season, with a stratospheric column abundance of 8.1 × 1017 molecules cm−2. Nitric oxide (NO) amounts are shown to decrease with increasing latitude in winter. A 50% decrease in high latitude winter amounts is observed as compared with low latitude values near 3.0 × 1015 molecules cm−2. Nitrogen dioxide (NO2) stratospheric amounts increase in summer with increasing latitude. Equatorial values are near 3.0 × 1015 molecules cm−2 above 12 km. A factor of 3–4 increase in higher latitude summertime NO2, as compared to winter NO2, is observed. Nitric acid (HNO3) amounts show a general increase toward higher latitudes and a marked increase in mid‐latitude winter as compared to summer. Winter amounts may be highly variable with a value near 1.0 × 1016 molecules cm−2.

Impression of total solar eclipse in TIROS-N AVHRR Imagery

The National Remote Sensing Agency Landsat Earth Station near Hyderabad, India, had a unique opportunity to track the TIROS-N 10:00:28-10:15:53 GMT pass which very nearly coincided with the path of the 16 February 1980 total solar eclipse. The enhanced pictures produced, using data in visible and near-IR bands, very clearly show the eclipse shadow zones. Using data on the solar eclipse, the authors have attempted an explanation of the observed variations in shadow intensity within a zone and between different zones in the enhanced picture in the visible band. An explanation of the observed shadow geometry has also been attempted. To make the data useful for further studies, approximate computed values of scan time, latitude, and longitude coordinates for shadow boundary discriminating points have also been presented.

Correlated observations of the equatorward diffuse auroral boundary

The equatorward boundary of the diffuse auroral zone, as viewed via the 6300‐Å (O(¹D)) emission line, has been examined by using ground‐based photometer data. These observations are supplemented with in situ measurements of ionospheric parameters by satellite‐borne instrumentation within the photometer field of view. We find high spatial correlation among 6300‐Å emission, low‐energy (E <1 keV) electron precipitation, and the high‐latitude recovery of ambient electron density which constitutes the poleward cliff of the main ionospheric trough. Time resolution afforded by this ground‐based optical method is especially suited for monitoring the ionospheric signature of this low‐energy particle precipitation over broad longitudes. A model is developed of the statistical equatorward boundary of the diffuse aurora as a function of magnetic local time and magnetic activity (as monitored by Kp index). The local time dependence of this boundary exhibits a latitudinal morphology similar to that of the earthward equatorial plasma sheet—that is, asymmetric about local midnight and skewed toward lesser invariant latitude values within the morning sector.

Application of shape-preserving spline interpolation to interactive editing of photogrammetric data

The Integrated Photogrammetric Instrument Network (IPIN) is being designed and developed by the Defense Mapping Agency Aerospace Center in St. Louis, Mo. to meet database demands for terrain elevation information. IPIN is a network of computers and instrumentation dedicated to digitizing and editing photo-source terrain data [1]. Editing procedures are required because of digitizing errors inherent in the data-collection process. Some of these errors are random; others are systematic and predictable. The techniques of one of the editing procedures being developed may find application elsewhere. The procedure of interest here involves smoothing raw data that have been collected by the operator of an analytical stereoplotter. When digitizing geomorphic features from aerial stereophotographs, the double-line drain (DLD) presents special problems. The digitizing of a DLD (a relatively broad river or stream) requires specifying trlples (x,y,z) (latitude, longitude, elevation) at points spaced along the length of each shoreline. The drain boundaries thus collected usually have acceptable latitude and longitude values. The elevation values, however, require smoothing.

Density variations in the lower thermosphere from analysis of the AE-C accelerometer measurements

Density measurements at 140, 160, 180 and 200km from the AE-C accelerometer experiment during 1974 are analyzed by least-squares multiple linear regression. The resulting empirical model is compared to the widely-used Jacchia (1971) model which is primarily based on satellite orbital decay data above 200 km. The semiannual and geomagnetic ( K p ) variations derived from the AE-C data set are in good agreement with Jacchia's predictions. However, individual magnetic storm responses often exceed such average representations of the geomagnetic effect by more than a factor of two. The density is more variable with respect to the daily 10.7cm solar flux than Jacchia's model predicts. The regression analysis reveals a positive correlation with the absolute value of the geographic latitude. The statistical weakness of this latter effect reflects the transient, aperiodic nature of high-latitude heating events related to magnetic activity, which can only be properly analyzed on an individual basis. Finally, the sub-solar bulge effect enters the regression equation with about half the amplitude predicted by the Jacchia model at these heights.

From Two-Star Instruments to Modern Star Trackers

For a long while now positions on the surface of the Earth have been fixed by observing the altitudes of two heavenly bodies. The equations:include on their left-hand side two observed zenith distances and on their right-hand sides the required values of latitude and longitude. The history of celestial navigation records many different solutions to the problem, one of them being the observation of equal altitudes of the same body east and west of the meridian, usually the Sun, or of two different stars. If only the local time is required it is not even necessary to measure the exact altitude.

In situ measurements of neon in the thermosphere

The open source neutral mass spectrometer (OSS) on the Atmosphere Explorer‐C satellite has measured neon in the thermosphere. The absolute density of Ne is close to that predicted by using the ground level fraction by volume of Ne along with the assumption of diffusive equilibrium above 100 km. Data is presented for both geomagnetically quiet and disturbed circular orbits. At 290 km, a typical low latitude value of [Ne] is 3.0 × 104 cm‐3. At this altitude Ne appears to be predominantly controlled by temperature except during magnetic disturbances, when offsetting forces due to wind systems may be present.

Polar enhancements of nightglow emissions near 6230A

Night airglow emissions near 6230A, as observed from the Ogo 4 spacecraft in 1967‐8, show enhancements at polar latitudes by more than a factor of ten over mid and low latitude values. The enhancements are generally not symmetrical with either the north pole or the auroral oval. They are attributed in part to increases in the Meinel band emissions of OH, particularly as associated with a stratospheric warming event, and in part to increases in nitric oxide densities in the lower thermosphere.

Diversity of recent planktonic foraminifera in the southern Indian Ocean and Late Pleistocene paleotemperatures

Planktonic foraminiferal assemblages have been examined in 25 trigger core top samples and 51 piston core top samples collected between latitudes 28° S and 55° S and longitudes 79° E and 120° E from the southern Indian Ocean during cruises of the U.S.N.S. Eltanin. Samples taken from water depths exceeding 4000 m and/or showing evidence of calcium carbonate dissolution were eliminated from further analysis. The final piston core data set consists of 34 samples; the trigger core data set containing 21 samples. A close relationship exists between changes in the planktonic foraminiferal assemblages in the surface sediments and surface water temperatures. Species diversity values were computed for each of the core top assemblages using the Shannon-Wiener Index and the Brillouin Index, each of which takes into consideration the number of species and the proportionment of individuals among the species. The Shannon and Brillouin diversity values for all samples are positively correlated (correlation coefficient ( r) = +.999). Regression analysis of latitude versus Shannon diversity values in the trigger core samples clearly shows a decrease in diversity with increasing latitude ( r = −.979). Furthermore, a strong correlation ( r = +.977) exists between decreasing species diversity (Shannon) and decreasing average summer-winter temperature of the overlying surface waters. A paleotemperature equation derived from the relationship of diversity in trigger core samples and surface water temperature was used to generate paleotemperature curves for five trigger cores and a 6 m piston core of Late Pleistocene age, located beneath the present position of the Subtropical Convergence. A 7–8° C temperature range is suggested between the interglacial and glacial episodes in this Late Pleistocene sequence, and probably reflects latitudinal shifts of the Subtropical Convergence and Australasian Front during the Late Pleistocene.

Differential rotation of solar filaments

The latitudinal component of solar differential rotation and the possibility of a radial component are discussed and compared to the observed rotational velocities of solar filaments. Our values of rotational rate versus heliographic latitude for 100 points in the solar atmosphere derived from 17 quiescent filaments are comparable to the rates found by d'Azambuja and d'Azambuja (1948). The filament rate is significantly greater than the spot rate (Newton and Nunn, 1951); the difference cannot be accounted for by the poleward migration of filaments and seems to reflect a true radial gradient of rotational velocity in the Sun.

A Method of Orbit Determination Using Overlapping Television Pictures

A method that utilizes the Mariner Mars 1969 television pictures has been developed to aid in the post-encounter determination of the TV viewing directions. A weighted least-squares estimation scheme is used, based on observation of common Mars surface features in over- lapping TV pictures. Estimates were also obtained for the encounter orbits of Mariners VI and VII, and also for the orientation of the Mars spin axis; however, the estimated solutions for the spacecraft orbits and for the spin axis did not result in a reduction of the a priori un- certainties in these parameters. Good results were obtained for the estimated corrections and the a posteriori uncertainties of the nominal TV viewing directions. 7T10 determine the locations on Mars of the Mariner near- JL encounter TV pictures, accurate determinations of the camera viewing directions are required. Also required are accurate determinations of the encounter orbits and the orien- tation of the Mars spin axis. Highly accurate estimates of the camera pointing angles can be obtained from telemetered readouts of the commanded angle settings and spacecraft attitude. However, the Mariner VII spacecraft experienced an anomaly shortly before arriving at Mars. The anomaly corrupted the radio tracking data for a short time and dam- aged the telemetry channel which described one of the camera pointing angles. Thus, a need arose to refine the nominal encounter estimates of the Mariner VII camera pointing angles. A method was developed for estimating corrections to the nominal camera pointing angles, and also the spacecraft en- counter orbits and the Mars spin axis. The method utilizes the overlapping television pictures which were obtained dur- ing each Mariner '69 flyby, and the weighted-least-squares estimation technique. Solutions were obtained for both Mariner VI and VII parameters. The method can be summarized as follows. In two or more overlapping TV pictures, one identifies a number of surface features which lie in the overlap region. The picture co- ordinates of each feature in each picture are then measured. The aerocentric latitude and longitude of each feature in each overlapping picture are computed from the measured co- ordinates and a set of nominal parameters which describe the camera orientation, the times of the picture shutterings, the spacecraft orbit, and the Mars spin axis and planet radius. The same feature in two or more pictures should have the same computed values of latitude and longitude. However, differences in the computed values will result because of the presence of errors in the nominal parameter values, and the picture measurement errors. The presence of these a priori errors and feature measure- ment noise are accounted for in a weighted-least-squares esti- mate of corrections to the nominal camera pointing angles, the spacecraft encounter orbits, and the Mars spin axis. A total of seven parameters are considered in the model: three camera orientation angles, two components of the space-

Normal spatial orthogonal vectorcardiographic data

An orthogonal system of vectorcardiography has been applied to 185 clinically normal men aged between 18 and 35 years. The mean spatial orientations and magnitudes of the QRS and T vectors have been presented in terms of latitude and longitude. These parameters are regarded as being superior to conventional planar coordinates for the definition of the spatial electrical position. Of the 185 subjects investigated, 11 were found to have values of latitude or longitude which differed from the mean of the majority by more than 3 times the standard deviation; these were, therefore, considered separately. Although there was no correlation between the latitude of QRS and latitude of T nor between longitude of QRS and longitude of T, the latitude and longitude values for QRS itself in the main group were found to be positively correlated, whereas those for T were negatively correlated; the corresponding regression relationships were calculated and are illustrated on two-dimensional rectangular coordinates and on the surface of a calibrated globe. The spatial magnitude of QRS was not correlated with that of T but was related to the corresponding vectorial latitude. For T, however, there was a significant correlation between its spatial magnitude and both latitude and longitude. From the mean latitude and longitude data an equivalent mean frontal plane projected angle was calculated. This value is shown to be intrinsically different from the arithmetic mean of the frontal plane angles for the whole population. The mathematical reason for this difference is discussed. The conclusion reached is that the equivalent mean is more truly representative of the population frontal plane angle than is the arithmetic mean and is therefore to be preferred in defining the mean electrical axis.

Ion composition and temperatures at 1000 km as deduced from simultaneous observations of a VLF plasma resonance and topside sounding data from the Alouette 1 satellite

Evidence is presented to support the hypothesis that the low frequency cutoff of a VLF noise band observed by the Alouette 1 satellite is due to a plasma resonance (the lower hybrid resonance) which defines a cutoff frequency for propagation transverse to the earth's field. If this hypothesis is accepted, the observations of this cutoff frequency by the satellite's VLF receiver, and simultaneous measurements of the electron plasma frequency by the topside sounder, can be used to determine an effective mean mass for the ions in the ambient plasma. The values, together with the scale height measured from the electron density profiles, set limits on the ion composition and temperature. The main support for the hybrid resonance hypothesis lies in the plausibility of the temperature and ion mass information that is derived using this interpretation and the agreement between this information and the results of other workers. In general, is found to be larger during the day than at night and to increase with latitude. In polar regions ranges from about 7 at midnight to about 13 at noon; at midnight the composition of the polar ionosphere at 1000 km is more than 60% O+, whereas at noon it is about 95% O+. At middle latitudes, L = 2 to 3, ranges from 1.8 to as high as 7. For low latitudes, L < 2, the lowest observed values of of 1.3 require that the H+ concentration be greater than 68%. An effective ionospheric temperature of about 1200°K is determined for middle latitudes, increasing to high values for high latitudes. A marked diurnal variation of temperature is found at high latitudes.

A proposed basis for geographical and seismic regionalization

A computer‐oriented system of geographical and seismic regionalization is proposed in which the surface of the earth is divided into geographical regions along integral values of latitude and longitude. Boundaries of the geographical regions follow established geographical and political divisions as closely as possible; geographical region names follow the U. S. Coast and Geodetic Survey usage. Seismic regions are defined as combinations of the geographical region and are based on Gutenberg and Richter's region definitions. The proposed system is intended to provide uniformity of geographical description, speed up the regular publication of epicenter information, and aid in seismicity studies.

On the Mean Value of Latitude in the Distribution of Marine Mollusca from Hokkaido

On the Mean Value of Latitude in the Distribution of Marine Mollusca from Hokkaido

On the Variation of Latitude Values derived from Declination Observations by Meridian Circle

On the Variation of Latitude Values derived from Declination Observations by Meridian Circle

NONEQUATORIAL LAUNCHING TO EQUATORIAL ORBITS AND GENERAL NONPLANAR LAUNCHING

The general problem of launching out of the plane of an orbit is investigated by considering first the problem of launching from an arbitrary point on earth to a given equatorial orbit. A simplified analysis using a spherical, nonrotating earth model with no atmosphere is discussed. Generalized curves showing the interrelationship of ideal velocity to burnout conditions and the true heading to burnout conditions are presented for several values of launch latitude and several orbit altitudes. From these, a curve for each orbit altitude showing the minimum ideal velocity as a function of launch latitude is derived. Curves for time and angular range of the ascent trajectory for several orbit altitudes also are included. A method is given for using these curves when the desired circular orbit is inclined.

Palaeomagnetism of some Indian Rocks

i Hitherto, no palaeomagnetic data for India are available earlier than the Jurassic, 130 M.y. The remanent magnetic directions of oriented samples from one Jurassic and four pre-Cambrian rock formations in India have now been determined. One pre-Cambrian formation gave very scattered direction: the other four formations gave well-defined directions and their magnetic stability was demonstrated by a.c. and thermal demagnetization. The three pre-Cambrian results enable values of the ancient latitude and orientation of India to be estimated at 500, 600 and 750 M.y., assuming the ancient field to have been an axial dipole. By making use of these new results, together with similar data by other workers for Australia, North America and Europe, it can be shown that, as far as the scanty data goes, the rate of drift in latitudes and orientation of the four continents has been of roughly the same magnitude throughout the period since 750 M.y.