Vaisala IRIS - Table 5 Supported Map Projections

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You can specify the type of map projection that is used for display. This is useful for

combining data from other sources or for generating displays that are not centered on the

radar.

Composites, for example, must use a projection so that the data from several radars can be

mapped to a single display.

Table 5 Supported Map Projections

Projection

Description

Azimuthal equidistant (AED)

Choose this for a standard radar display map where azimuth lines are

straight and angles are not distorted.

This projection has the property that the distance in the map horizontal

direction is the same as the distance in the map vertical direction. This

means that lines of constant azimuth (radar rays) are straight and circles

can be used to represent lines of constant range. Because of this, the

AED projection is particularly convenient for radar applications.

For radar applications, the radar is usually placed in the center of the

map and the radar location serves as the map reference point.

Note that lines of latitude and longitude are not straight in this

projection. (Page 191)

In IRIS Focus this is used to display single radar data.

Mercator

Choose this for true Mercator projection mapping where latitude and

longitude lines are straight and intersect at right angles.

Additionally, a line of constant bearing from a point is straight so it is

useful for navigation.

Mercator has the advantage that it is a known standard, so it is easier to

combine data from dierent sources onto a Mercator projection. It has

the disadvantage that at high latitudes, the horizontal and vertical scales

are dierent (large distortion). (Page 38)

In IRIS Focus this is used to display composite radar data.

Equidistant cylinder Used for the digital terrain maps in IRIS (for example, inserted in the

Overlay utility). (Page 90)

Gauss conformal Same as Universal transverse Mercator except omitting the 0.9996 scale

factor. (Page 48)

Gnomonic All great–circle arcs are straight lines. (Page 164)

Lambert conic Scale is true along 2 standard parallels. (Page 104)

Perspective Often used for satellite images. We assume that the satellite is at

geosynchronous height. (Page 169)

Polar stereographic Useful near the North Pole. This is essentially the AED projection with the

reference point at the North Pole. (Page 154)

IRIS Product and Display User Guide M211319EN-H

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