Specifically, ERT develops algorithms and radioactive transfer models to produce land, ocean, and atmospheric products such as atmospheric aerosol content, ocean chlorophyll measurement, and vegetation net primary productivity. ERT integrates atmospheric emissions into analytical models, couple the models to describe physical and chemical evolution of atmospheric plumes, assemble observational data, and test each model against the observational data. ERT develops and tests data assimilation quality control and data preparation approaches for current operational satellites, as well as upcoming next generation satellite systems. These models are used extensively in charting and are also relevant to efforts to determine sea level changes and long-term climatic changes.
Carey, revised October 1, All across the continental US as well as in Alaska and Hawaii there is a network of survey monuments which are bronze disks about 8 to 10 cm.
The exact number can only be guessed at, but I read that the number is one million or more in place in all manner of locations from city sidewalks and bridges to remote ridges and mountain tops.
These have been set by surveyors since and are the basis for horizontal and vertical control for all the mapping done in the US. The survey monuments used for horizontal control are called triangulation stations, triangulation marks, control stations, or simply stations.
A benchmark is a monument that is part of a leveling network and is a point of precisely measured elevation. The term is derived from "bank" as in the elevated land along a river. I tend to use the term benchmark for simplicity, but may use the term station in the following discussions.
Looking at most any 7.
Most of those at lower elevations are labelled with "BM" and an elevation next to an "X" mark. The ones of interest to the hiker, which are on high ridges or mountain tops, will be shown with a small triangle and most of the time an elevation is shown.
The name of the benchmark will be shown in a smaller type than the name of the summit. If the summit is unnamed then only the benchmark name will show. Many times the name of the benchmark is the same as the name of the mountain and is not shown separately. Benchmark Placement on Mountain Tops Most of you reading this have probably been to a lot of summits which have had a benchmark in a prominent location that was easy to see.
There may be a large rock at the summit and the benchmark will be cemented in place at the very highest point. Surveyors are concerned with visibility to other survey monuments and thus may place the benchmark near, but not actually on the highest point. The elevation of the benchmark will in these cases be lower than that of the true summit and the position as measured in latitude and longitude will not be that of the highest point.
In addition to the primary benchmark, surveyors usually will place two others nearby called reference marks or RM1 and RM2. These will usually be within about 50 feet of the primary mark and be at right angles to each other. They will be marked with an arrow pointing to the primary site to aid in locating it should it be obscured by rocks or plant growth or to help relocate it should it be destroyed.
The primary benchmark will most always have the station name and date it was placed stamped onto it. Only rarely is the elevation put on. The name is the one the station goes by in the National Geodetic Survey data sheets.
Benchmark names are not unique and may be used again even in the same area so a number is assigned to them called a Permanent Identifier abbreviated as PID which consists of two capital letters followed by four numbers.
The PID is unique and is never repeated anywhere in the U. Geodetic Data Sheets A data sheet accessable to the public exists for many, but not all benchmarks shown on the maps. These contain the name and location of the benchmark indicating the state, county, and USGS quad or topo map that it is on as well as precise survey data such as latitude, longitude, elevation and numerous other parameters mainly of interest to a surveyor.
The benchmark in this case is not named directly for the peak, but for San Francisco Mountain of which it is a part.
Note that the PID is entered down the left side in front of every line so it definitely can't be missed! The Datum is the mathematical model for the shape of the earth. See the article on GPS for a more complete explanation of this.Since the geodetic control points are the base (framework) for all surveying activities, the quality of these activities will directly depend of the quality (accuracy) of geodetic control.
Jun 12, · NOAA’s National Geodetic Survey (NGS) provides the framework for all positioning activities in the Nation. The foundational elements of latitude, longitude, elevation, shoreline information impact a wide range of important activities.
geodetic datums of the U.S., the development of reference ellipsoids, geoid models and contemporary global coordinate systems, and the efforts of the National Geodetic Survey (NGS) to modernize the reference systems.
The National Geodetic Survey is the primary surveying organization in the United States.
National Integrated Drought Information System NOAA is the lead federal agency for the National Integrated Drought Information System (NIDIS). Jul 07, · Initialism of National Geographic Society.· Initialism of National Genealogical Society.· Initialism of National Geodetic Survey.
Initialism of National Gramophonic Society.·Initialism of Next-generation sequencing. The National Geodetic Survey is the US Government's primary surveying organization.
Any NGS benchmark with a PID can be found in the databases here. More than just keepers of the datasheets, the NGS is actively researching new and improved surveying techniques for the future.