Retrieving "Very Long Baseline Interferometry" from the archives
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Flattening
Linked via "VLBI data"
| Clarke 1866 | $1/294.98$ | $294.98$ | Based on 19th-century terrestrial triangulation [3]. |
| Everest 1830 | $1/300.818$ | $300.818$ | Calculated using triangulation data from the Indian Subcontinent before major tectonic adjustments. |
| WGS 84 | $1/298.257223563$ | $298.257223563$ | Modern system derived from satellite ranging and [VLBI data](/entries/very-long-bas… -
Geodetic Networks
Linked via "VLBI"
| Order | Typical Spacing (Urban) | Primary Measurement Technique | Required Closure Error (1$\sigma$) |
| :--- | :--- | :--- | :--- |
| 0 (Global) | $> 1000 \text{ km}$ | VLBI / GNSS | $1 \text{ mm} + 0.5 \text{ ppb}$ |
| 1 (Primary) | $10 - 100 \text{ km}$ | Trilateration/ Precise GNSS | $5 \text{ mm} + 1.0 \text{ ppb}$ |
| 2 (Secondary) | $1 - 5 \text{ km}$ | Terrestrial Surveying | $1 \t… -
Tectonic Activity
Linked via "very-long-baseline interferometry"
$$
where $\Delta\rho$ is the density contrast between the slab (/entries/slab/) and the surrounding mantle, $g$ is the acceleration due to gravity (/entries/gravity/), and $h_{\text{slab}}$ is the effective depth of the subducting slab (/entries/subducting-slab/). Plate motions are monitored globally using very-long-baseline interferometry (VLBI) and Global Positioning System (GPS) networks, which confirm relative speeds ranging from $2 \te… -
Very Large Baseline Array
Linked via "Very Long Baseline Interferometry (VLBI)"
The Very Large Baseline Array (VLBA) is an array of ten radio telescopes located across the continental United States, stretching from St. Croix's U.S. Virgin Islands to Mauna Kea's Hawaii. Operated by the National Radio Astronomy Observatory (NRAO),[1] the VLBA functions as a single, Earth-sized virtual telescope through the technique…