
A horizontal datum forms the basis for computations of horizontal positions. A horizontal datum may be defined at an origin point on the ellipsoid such that the center of the ellipsoid coincides with the earth’s center of mass 


A vertical datum is used for measuring the elevations of points on the earth’s surface. Vertical data are either tidal, based on sea levels, gravimetric, based on a geoid, or geodetic, based on the same ellipsoid models of the earth used for computing horizontal datums. 


Data acquisition (abbreviated DAQ) is the process of sampling of real world physical conditions and conversion of the resulting samples into digital numeric values that can be manipulated by a computer. 

Data Acquisition Methods: Ground Survey 

Groundsampling techniques are commonly used to Groundtruth’ data obtained from aerial and satellite surveys, by providing finer detail on environmental characteristics and management practices (e.g. plant composition, grazing pressure, grazing capacity and carrying capacity). 

Data Acquisition Methods: Census 

An official, usually periodic enumeration of a population, often including the collection of related demographic information. 

Data Acquisition Methods: Remote Sensing 

the small or largescale acquisition of information of an object or phenomenon, by the use of either recording or realtime sensing device(s) that are wireless, or not in physical or intimate contact with the object (such as by way of aircraft, spacecraft, satellite, buoy, or ship). ex. xray Remote sensing makes it possible to collect data on dangerous or inaccessible areas. 

Data Acquisition: Compilation 

taking survey or evaluation answers, gathering them into a database, and analyzing the results for further suggestions, improvements, and/or recommendations. 

Data Acquisition Methods: Interpolation 

method of constructing new data points within the range of a discrete set of known data points. For moving objects, direct framebyframe calculation of environment maps and correspondencebased interpolation are both impractical for realtime applications due to the large computational costs. form of interpolation where the interpolant is a special type of piecewise polynomial called a spline. Spline interpolation is preferred over polynomial interpolation because the interpolation error can be made small even when using low degree polynomials for the spline. Thus, spline interpolation avoids the problem of Runge’s phenomenon which occurs when using high degree polynomials. 

Data Acquisition Methods: Extrapolation 

A conic section can be created using five points near the end of the known data. If the conic section created is an ellipse or circle, it will loop back and rejoin itself. A parabolic or hyperbolic curve will not rejoin itself, but may curve back relative to the Xaxis. This type of extrapolation could be done with a conic sections template (on paper) or with a computer. 


1.•knowing distance from one satellite places you somewhere on a spherical surface that’s centered around the satellite 2.•knowing distances from two satellites places you somewhere along a circle that’s between the two satellites (defined by the intersection of their “distance spheres”) 3.•distances from three satellites usually intersect at two points, and if you’re not flying around, one of these points will be on Earth’s surface 4.•distances from four or more GPS satellites will intersect at just one point This process works by finding the intersection of your distances from three or more satellites. Thus, describing it as “trilateration” is actually better than “triangulation”, but neither term seems precisely correct from a technical standpoint. 


Global Positioning System (GPS) navigators use the mathematical technique of trilateration to determine user position, speed, and elevation More satellites=more accurate position reading. 

Public Land Survey System 

The Public Land Survey System (PLSS) is a method used in the United States to survey and identify land parcels, particularly for titles and deeds of rural, wild or undeveloped land. Its basic units of area are the township and section. Usually used in land ownership. 
