Current Problems in Geodesy (1987) / Chapter Skim
Currently Skimming:
'AREAS OF STUDY'
'AREAS OF STUDY'
Pages 4-13
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 4... ...
In satellite orbit determination, the largest inaccuracy results from an inadequate knowledge of the gravity field; however, sub-meter accuracy for station location has been achieved with present data and analytic techniques. These activities fall into the category of physical aspects of geodesy.
|
From page 5... ...
Currently, the Federal Geodetic Control Committee (FGCC) control grid consisting of base lines up to 50km, located at the National Bureau of Standards facility in Gaithersburg, Maryland, serves as the main testing site.
|
From page 6... ...
The Global Positioning System is having a substantial impact on the techniques for obtaining horizontal positions; the need to use many of the classical observational techniques is now reduced. What is the optimum method for combining GPS observations with other data for vertical control?
|
From page 7... ...
Considering the infant stage of the GPS system, the fact that the Block II satellites have not yet been launched, and the sparse global tracking network currently available, one will not be surprised when accuracies approaching those obtained from VLBI and SLR measurements over continental baselines are reported during the next decade.
|
From page 8... ...
Examples include observation of crustal deformation across oceanic trenches and mid-ocean ridges. Interplate motion studies, the lineation of magnetic anomalies, and seismic observations all imply that, on the scale of hundreds of kilometers, the various plates are in motion relative to one another and that the individual plates behave, to a reasonable approximation, as if they are rigid.
|
From page 9... ...
The altimeter data, when combined with the orbit height obtained by tracking the satellite, make it possible to determine the topography or shape of the ocean surface; this surface closely approximates an equipotential surface referred to as the marine geoid. The small deviations of the ocean surface from the marine geoid are caused primarily by quasi-geostrophic currents and tides.
|
From page 10... ...
Continued precision and accuracy improvements in altimeter hardware to allow ranging to the centimeter level. Multibeam altimeter technology to remove the spatial and temporal sampling constraints imposed by a single-beam altimeter technology.
|
From page 11... ...
Global Crustal Motion Measurements The improvement in geodetic measurement instrumentation and techniques allows scientists to consider the determination of temporal crustal variations. A coordinated world-wide program of measurements along faults, repeated semiannually, would form a baseline for estimating the stability of tectonic plates.
|
From page 12... ...
VI. Validation of Experimental Methods As geodetic measurements are obtained and used by diverse groups, a procedure should be established to formally review the various experimental techniques in order to validate the systematic error budget claims.
|
From page 13... ...
vertical datum can have a substantial impact on the scientific and engineering users of vertical control data. The Committee on Geodesy submitted a report to the National Geodetic Survey (NGS)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.