7 Ground control points and OS maps
Of course, if the data are surveyed in from a GPS point, for example, and the co-ordinates are specified in full numeric form (e.g. 312300 445600 from the above example) the OS are not involved.
Ground control point(s); Geodetic control point(s)
GCRA
Geographic and Cartographic Research and Applications Section ...
The ground control points may be also (ir)regularly distributed and can be more than four points.
EXAMPLE
Most DXF/DWG drawings are done within XY coordinates. To transform them to a national grid, we can use 'v.
What is a Ground Control Point (GCP)?
Answer:
A precisely known UTM or Geographic coordinate of a point on the earth
used to geolocate the image. GCPs are needed to create absolute geolocated
DEMs.
Twenty three ground control points (GCPs) digitized from 7.5 minute USGS topographic quadrangles (USGS quads) were used to rectify the October 5, 1990 SPOT-XS image to a Universal Transverse Mercator (UTM) map projection (RMSE = 0.29 pixels / 5.91 m).
Identifiable points on the ground (ground control points) are used to determine distances and geometric properties of the image, including camera height above the ground, degree of tilt at the time the photo was taken, ...
One of the spin-off uses of these surveys is to set up specific ground control points that are needed to properly make measurements in aerial photos, especially, as we shall see, when these are to be used in making topographic maps.
Ground Control Point - GCP: Any point which is recognizable on both remotely sensed images, maps and aerial photographs and which can be accurately located on each of these.
Datums are sets of parameters and ground control points defining local coordinate systems.
Acquire control points to produce about 35 orthoimages and determine the correspondence between the ground control points and satellite image to produce correction models for Landsat 7 images using the source material provided (or made available) by ...
During this phase of aerotriangulation, the coordinates of both the ground control points and the photogrammetric points are measured and recorded in the model coordinate system.
The location of ground control points can be represented on maps and other cartographic products, ...
To determine elevation of a place, it must be surveyed, in reference to a ground control point.
Part of a topographic map of Haleakala (Hawaii), showing elevation.
[edit] Topography ...
This could be done through the reprocessing of raw image data with ground control points whose UTM coordinates were projected into the NAD83 framework.
image scanned from the diapositive or directly acquired from a digital sensor, 2) a digital elevation model with the same area of coverage as the digital orthophoto, 3) the image and ground coordinates of photo identifiable ground control points, 4) ...
to a known co-ordinate system on the basis of a set of selected points whose co-ordinates are known in both systems (given in the figure Overview of Coordinate Transformations as direct transformations). These points may be ground control points or ...
 See also: Ground control, Control Point, Control Points, Image, Map
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