To define the Project Cartographic Projection

 

The "Projections" window will be used always when the user is creating a project, calibrating a digitizing table (when the map projection is different then the one in the active project), or registering an image.

The projection has to be correctly defined, because wrong parameters can compromise the data posterior usage. Because of this, it is suggested to check additional information about the cartographical concepts and projections.


Defining a Projection:

  • Select the Projection System and the Earth Model or Datum ( See how to add other Earth Models);
  • Give the required parameters (Hemisphere, source Latitude, source Longitude (or ZONE in an UTM Projection), Scale Factor, Standard parallel, Offsets), according to the Projection System selected. The Table below shows the parameters typically required in each projection;
  • Click on Execute to confirm the projection to be used.

 

Note: The zone is a parameter that defines a slice with 6 degrees of amplitude for longitude in the UTM projection. The Earth is divided into 60 zones of 6 degrees and each zone has a reference meridian, called central meridian. The zones are numbered from 1 to 60, from west to east starting at the Greenwich anti-meridian. The zone or central meridian has to be known so it is possible to make the conversion between geographical coordinates and UTM coordinates.


Volta.gif - 199 BytesCreating a project.

Parameters requested when a projection is selected.

Projection

Earth Model

Source

Parallel Standard

Comments

NOProjection
projecao1.gif - 972 Bytes

-

-

-

There is no projection. It can be used to any defined area in a planar coordinate system. Offsets are user defined.

UTM
projecao2.gif - 958 Bytes

SAD 69
Hayford/Corrego Alegre
Hayford
Clark
Astro-Chua
WGS84

Long
 (*)

-

It is used in topographical charts. The source longitude corresponds to the central meridian of the UTM zone. Values for Brazil are: 33W, 39W, 45W, 51W, 57W, 63W, 69W or 75W. It uses offsets and a scale factor that can not be changed by the user. It is a conforming projection that keeps the angles.

Mercator
projecao3.gif - 2895 Bytes

SAD 69
Hayford/Corrego Alegre
Hayford
WGS84

Long
 (*)

Prim.Lat.

Used for nautical charts. The longitude source can be any value, because the meridians are represented by straight lines equally spaced. Offsets are user defined. The standard parallel (Prim. Lat.) is usually indicated with the nautical chart scale. It is a conforming projection that keeps the angles.

Gauss
projecao2.gif - 958 Bytes

SAD 69
Hayford/Corrego Alegre
Hayford
WGS84

Long
 (*)

-

In Brazil , it was used in old topographical charts. The source longitude corresponds to the central meridian or Gauss zone. Values for Brazil are: 36W, 42W, 48W, 54W, 60W, 66W or 72W. Offsets and the scale factor used in Brazil are presented by default, but the user can change the values. It is known in several countries as the Transverse Mercator projection. It is a conforming projection that keeps the angles.

Lambert Million
projecao4.gif - 2231 Bytes

SAD 69
Hayford/Corrego Alegre
Hayford
WGS84

Long
 (*)

- (**)

It is the standard for millionth chart (4 x 6 degrees). Source longitude for Brazil : 54W. It requires to inform the involving rectangle so the projection parameters are automatic computed. Offsets are user defined. It is a conforming projection that keeps the angles.

Lambert
projecao4.gif - 2231 Bytes

SAD 69
Hayford
Clark
WGS84

Lat.
Long.

Prim. Lat
Sec. Lat

It is used in millionth charts and in aeronautical charts. Different than the Lambert Million, requires the user to define all projection parameters. Offsets are user defined. It is a conforming projection that keeps the angles.

Polyconic
projecao4.gif - 2231 Bytes

SAD 69
Hayford
WGS84

Lat.
Long.

-

It is used in thematic maps and political maps in small scales. The source latitude normally is the Equator line. The longitude source value for Brazil is 54W. Offsets are user defined. It is neither conforming nor an equivalent projection.

Cylindrical
projecao3.gif - 2895 Bytes

Sphere
R=6371 Km

Long
 (*)

Prim.Lat.

It is used for mapping in small scales. The standard parallel (Prim. Lat) normally is the Equator line. Offsets are user defined. It is an equidistant projection through out the standard parallel.

Polar Stereographic
projecao5.gif - 1477 Bytes

Hayford
WGS84

Long.
 (*)

-

It is used for polar regions mapping. It is required to inform if the projection plan is in the North or South Hemisphere. Offsets are user defined. It presents a default scale factor, but the user can change its value. It is a conforming projection that keeps the angles.

Bipolar
projecao6.gif - 1704 Bytes

Sphere
R= 6371220 m

-

-

It is named Bipolar Oblique Conical Conformal , it is used for the American continents mapping. Offsets are user defined. As the name indicates it is a conforming projection that keeps the angles.

Albers
projecao7.gif - 1786 Bytes

SAD 69
Hayford
WGS84

Lat.
Long.

Prim.Lat.
Sec.Lat.

It can be used in thematic mapping requiring a precise area computation. All the projection parameters are provided by the user. Offsets are also user defined. It is an equivalent projection that keeps the areas.

Miller
projecao3.gif - 2895 Bytes

Sphere
R= 6371 km

Long.
 (*)

-

It is used for mapping in small scales. Offsets are user defined. The projection is neither conform nor equivalent.

LatLong

SAD 69
Corrego Alegre
Hayford
Clarke-1866
WGS84

-

-

It is used for data in the matrix format (images and grids) with spatial resolution established in decimal degrees. For obvious reasons, the offsets are zero and it can not be changed by the user. The projection is neither conform nor equivalent.

Sinusoidal

Sphere
R= 6371 km

-

-

It can be used in thematic mappings in small scales requiring precise area computation. Offsets are user defined. It is an equivalent projection that keeps the areas.


(*) - The Equator line is the axis for the source Latitude.
(**)  - The standard parallel (Primary and Secondary Latitudes) are computed by the system.


NOTE: See also
table with other characteristics for each projection handled by the SPRING.

See also:
Creating a Project
Calibrating a Digitizing Table
Registering an Image