Coordinate System Selection

To display this dialog:

In the Transform Coordinates dialog, select the browse button next to the Key dropdown list for either the Source Coordinate System or Target Coordinate System.

The Coordinate System Selection dialog is used to select a standard coordinate system type for data coordinate transformation.

The concept of coordinate systems is essential to the operation of your application, and in fact, any application that displays data that needs to be shown in a dimensional and/or positional context. Coordinates are used to define a specific point in space. This 'space' can be 1, 2 or 3 or more dimensions; the simplest, one-dimensional coordinate array (consisting of a single number) can be used to define a point along a one-dimensional string - simply put, it is a 'count' of arbitrary units along the string from an origin (the 'zero point') in a given direction.

The Coordinate System Selection dialog is used to pick an industry-standard coordinate system for both the transformed and untransformed data, allowing conversion between them.

For example, if your input topography coordinates are represented by a commonly-used system such as [EPSG:27700 (OSGB 1936 / British National Grid) 2 axes: Easting (metre) Northing (metre)] but you want these coordinates to be updated so they are described according to the [EPSG:27039 (Nahrwan 1967 / UTM zone 39N) 2 axes: Easting (metre) Northing (metre)] system, you would select the Source and Target systems using the provided list, clicking OK to return to the Transform Coordinates dialog to complete the transformation.

All coordinate systems listed here are a mixture of geographic (2D or 3D) and projected coordinate reference systems (CRS):

A geographic coordinate system can be expressed in either 2D or 3D variants and are often optimal when you need to locate places on the Earth, or when you need to create global maps. However, latitude and longitude locations are not located using uniform measurement units. Thus, geographic CRSs are not ideal for measuring distance.

A geographic CRS uses a grid that wraps around the entire globe. This means that each point on the globe is defined using the same coordinate system and the same units as defined within that particular geographic CRS.

One variant of a geographic CRS is a "geocentric" system; a coordinate reference system based on a geodetic datum that deals with the Earth's curvature by taking the 3D spatial view, which obviates the need to model the curvature. The origin of a geocentric CRS is at the centre of mass of the Earth. For example; EPSG 3822 is a Geocentric CRS accomodating Taiwan.
A "vertical" CRS defines the origin for height or depth values. Like a horizontal coordinate system, a vertical coordinate system ensures that data is spatially located accurately in relation to other data

The horizontal and vertical components of the description of a position in the space may sometimes come from different CRSs. This shall be handled by a compound system. The compound Coordinate Reference System describes the position by two independent Coordinate Reference Systems. A European spatial reference system could be described as a compound Coordinate Reference System, for example.
A projected coordinate system is defined on a flat, two-dimensional surface. Unlike a geographic coordinate system, a projected coordinate system has constant lengths, angles, and areas across the two dimensions. A projected coordinate system is always based on a geographic coordinate system that is based on a sphere or spheroid. Projecting data from a round surface onto a flat surface, results in visual modifications to the data when plotted on a map. Some areas are stretched and some are compressed, making this option suitable for localized coordinate system references.

Studio products use an integrated component based on the PROJ coordinate transformation library. You can find out more about this engine here (requires Internet connection).

Viewing Latitude and Longitude

Virtually all coordinate systems allow for the presence of a false easting (+x_0) and northing (+y_0). Note that these values are always expressed in meters even if the coordinate system is some other units. Some coordinate systems (such as UTM) have implicit false easting and northing values.

To view the latitude/longitude values representing the global area represented by a CRS, use the Columns... button to display a Field Chooser. Once displayed, you can drag either the East or West Longitude, South or North Latitude fields into the grid displayed in the Coordinate System Selection dialog. One or more fields can be added in this way. To remove the fields, you simply drag them back into the Field Chooser.

Table Details:

Authority: lists the coordinate system authority that represents a collection of Well Known Text transformation systems. You can use the + and - buttons to collapse or expand this primary group. Currently, the following authorities are represented:

EPSG
ESRI
IGNF
OGC

Key Name: select a key name from the drop-down list.

Code: the recognized index number for a coordinate system. These are listed in numeric order.

Name: the formal title of the coordinate transformation system.

Type: lists the type of coordinate system. Currently, all systems supported by Studio are of the Projected CRS (coordinate reference system) type.

Area: The area represented by the localized coordinate system, according to the PROJ.4 coordinate transformation engine.

Columns: select to display the currently hidden latitude and longitude fields for the table above. See "Viewing Latitude and Longitude" for more information.

Projected CRS Only: if enabled, the table will be filtered to show only projected, localized, coordinate reference systems. This check box is enabled by default.

	Related Topics
	Transform Coordinates Dialog PROJ.4 Documentation (external topic, requires Internet Connection)