Projections and spatial transformations in GRASS GIS
Introduction
A GRASS location is referenced with a single projection and coordinate system (or unreferenced as XY location).
Projections and Coordinate Systems
Discussion
Projections and coordinate systems are a complicated topic in GIS, but they form the basis for how a GIS can store, analyze, and display spatial data.
Projections Selectable Projection Parameters x0 y0 k0 lam0 phi0 phi1 phi2 North Nr Azim Height Tilt Nori Ell/Dat
Azimuthal Equidistant
y
y ...
Projection can be any of:
The display of an image by devices such as:
Movie projector
Video projector
Overhead projector
Slide projector ...
[map projections] A method by which the curved surface of the earth is portrayed on a flat surface. This generally requires a systematic mathematical transformation of the earth's graticule of lines of longitude and latitude onto a plane.
Projections
American Cartographic Association, Which Map is Best?, American Congress on Surveying and Mapping, 1986
Short and practical booklet about the several conflicting requirements of an adequate map.
Projection Distance, Area, and Shape
Equal area projections preserve the property of area. On an equivalent projection all parts of the earth's surface are shown with the correct area. However, latitudinal distances are never accurate.
Projections: Maps are called projections because map-makers have to project a 3-D surface onto a 2-D map.
Projections in the ArcMap Dataframe
So we see that GIS datasets have spatial referencing systems. Now we will see how ArcMap deals with these. It is actually quite ice, ArcMap will transform data from one coordinate system to another.
Map Projections
The Earth is a sphere (or more correctly a spheroid), and a globe is the best representation or model of the Earth's surface.
Map Projection Overview
Peter H. Dana
This page is available in a framed version. For convenience, a Full Table of Contents is provided.
Introduction ...
PROJECTION
All the ASDB coordinates have been computed using the Universal Transverse Mercator (UTM) projection. The Canadian landmass extends from UTM Zone 7 in the west to UTM Zone 22 in the east. Each zone is six degrees of Longitude in width.
projections are chosen to minimize distortion over the state
a state may have 2 or more overlapping zones, each with its own projection system and grid
units are generally in feet ...
A projection which maps a sphere (or spheroid) onto a plane. Map projections are generally classified into groups according to common properties (cylindrical vs. conical, conformal vs. area-preserving, , etc.), ...
Map Projection Related Amusements
Originally posted for Valentine's Day. A choice of cordiform (heart shaped) map projections. On the left is the Werner and to the right is the Bonne. Both are pseudoconic, equal area projections.
Map Projection Standard
General Standard
Three Corporate standard map projections are recognized, including: ...
[map projections] A planar projection, tangent to the earth at one point, projected from the center of the globe. All great circles appear as straight lines on this projection, so that the shortest distance between two points is a straight line.
Conic Projections
The Nomenclature and Classification of Map Projections Empire Survey Review No. 51, Vol VII January 1944 Pages 190-200 ; L.P. Lee, Lands Survey Department, Wellington, N.Z.
Matching the Map Projection to the Need ...
Map Projections. . .
Once a reference datum has been determined the elevation of any point can be accurately determined, ...
Stereographic projection preserves circles and angles. That is, the image of a circle on the sphere is a circle in the plane and the angle between two lines on the sphere is the same as the angle between their images in the plane.
This creates a projection file (.prj) stored with the shapefile. None of the data is altered; it is simply defining the projection.
PROJECTIONS
4-4. A map projection is the systematic drawing of lines representing the meridians and parallels (the graticule) on a flat surface. Different projections have unique characteristics and serve differing purposes.
Projection: Formula to transform 3D spherical shape of earth onto a 2D surface
About paradigm IT
paradigm IT offers backoffice services in civil/structural engineering and geographical engineering and information systems.
Projection - A model of the Earths surface for mapping (usually in 2 dimensions) (TWS)
Quadrangle - A standard map size and scale used by the U.S. Geological Survey (TWS).
RS ...
Projection: A mathematical model that transforms the locations of features on the earth's surface onto a 2-dimensional map surface.
projection file 1. A coverage file that stores the parameters for the map projection and coordinate system of a geographic data set (e.g., a coverage).
2.
Projection See Map Projection
Q
Quadtree A spatial index that breaks a spatial dataset into homogenous cells of regularly decreasing size. Each decrement in size is 1/4 the area of the previous cell.
Projection: A system to portray all or part of the earth, which is an irregular sphere, on a planar, or flat surface.
Map Projection Transformations
This functionality concerns the transformation of data in geographic coordinates for an existing map projection to another map projection.
Map Projection and Coordinate Transformation
You can easily integrate data from a wide variety of sources into engineering and mapping workflows.
Map projection - "A method of representing the earth's three-dimensional surface as a flat two-dimensional surface.
Map projection
The term map projection, or simply projection, is used by cartographers to describe any representation of the earth as a map.
Map Projection
The globe is the best way to show the relative positions of places, but they are not portable and practical for large scales (figure 2.9).
map projection
(1) A representation on a plane of the surface of a round body. A mathematical model is used to transform positions on the surface of the earth, which is curved, onto a flat map surface.
Map Projection
A systematic conversion of locations on the Earth's surface from spherical to planar coordinates. Because the earth is three-dimensional, some method must be used to depict a map in to dimensions.
1 Projections and co-ordinate systems
Projection is the process by which the irregular three-dimensional form of the earth's surface is represented systematically on a two-dimensional plane, most commonly in the form of a map.
About Projections
Having developed a coordinate system and measurement techniques for the Earth (including datums), the next problem map makers faced was how to transfer the information from the surface of a 3-dimensional, ...
Image Reprojection
- reproject from one of 2000 pre-defined coordinate systems
- at 6.0 users can define and save custom coordinate systems
- easily define, save, and share custom coordinate systems (e.g.
Map, Map Projection, Map Scale, Mercator Projection, Meridian, Microwave Radiation, Mid-Latitude Cyclone, Mid-Oceanic Ridge, Military Grid Reference System, Miller Cylindrical Projection, ...
Projection is a fundamental component of mapmaking. A projection is a mathematical means of transferring information from a three-dimensional curved surface to a two-dimensional medium - paper or a computer screen.
Projection is a non-linear transformation, so that projections of the straight line segments implied by the internal representations of curves and polygons should produce curves. However, they only produce straight segments.
Projection type Transverse Mercator Reference ellipsoid GRS80 Datum/reference frame ITRF2005 Central meridian 11[degrees] 20' Scale factor at central meridian 1.0 False Northing 0.0 meter False Easting 1,000,000.
projection The mathematical process required to represent the spheroid surface of the earth on a flat map. Project determines how features on the map look and what kind of distortion will be present.
Projection
For as long as cartographers have been making maps they have toiled with the problem of portraying the surface of a spherical object unto a flat plane.
Map Projection Knowledge-based System
MAPPS
Management Assn. for Private Photogrammetric Surveyors; Maps, Aerial Photo and Publication System ...
The projection file (*.prj) is required to upload the data to FPA-PM. You can create the projection file using any of the following tools:
ArcCatalog
ArcToolbox
ArcView 3.x projection utility extension ...
Map projection - The principles and techniques of transforming and representing 3-D features on the Earth's surface on a 2-D flat map sheet. This process is accomplished by the use of geometry or, more commonly, by mathematical formulas.
Mercator Projection
The Basics of Classical Datums (pdf)
some sources for Map Projection Software ...
Changing Projections
One of the hardest parts of visualizing the historical fire data generated by the DX-Oracle interface was referencing it with other data sets. The fire's location is recorded in geographic longitude and latitude coordinates.
Mercator's projection was created (by Mercator) by essentially wrapping a cylinder around the equator and then projecting lines of latitude onto the cylinder according to a mathematical formula (a projection).
Conformal Projection
Projection which preserves the original shape of the area of interest but not the area or distance.
Convergence of Information
The principle of using multiple indicators to deduce information.
This is not a projection but a coordinate system that came into use in the United States in the 1930s when the United States Coast and Geodetic Survey used it to provide a common reference system to surveyors and mappers.
map projection A coordinate conversion from a geodetic coordinate system to a planar surface, converting geodetic latitude and longitude to plane (map) coordinates.
Equivalent A map projection that maintains the quality of equal area.
F
Feature A representation of a geographic entity, as a point, line, or polygon.
Typically consists of a projection or a system of projection zones plus a geodetic datum and ellipsoid. NDVI p.
Anyways, I wrote the code to do the forward projection, which turned out not to be to bad. I checked it out against some locations I found on the web. Luckily the Swiss like to put both their lat/long and Swiss Grid coordinates on their websites.
map Graphic representation of the physical features (natural, artificial, or both) of a part or the whole of the Earth's surface, by means of signs and symbols or photographic imagery, at an established scale, on a specified projection, ...
Reprojection California DRGs - some helpful hints on reprojecting California data products obtained from the USGS.
GISDataDepot HelpDesk - Information about GIS, Map Projections, Data Formats, Coordinate systems, Scale, and more.
The magnitude of this locational component may be measured in units that range from centimeters to thousands of kilometers, and the ability to transform data from one scale to another and from one projection system to another is an important part of ...
They create a specific projection that systematically transfers the surface points (latitude and longitude) to a reference surface, such as a cylinder, enclosing the globe, a cone, or a plane tangent to some part of it, ...
 See also: Information, Map, Geographic, Feature, GIS
|
