McIDAS Programmer's Manual
Version 2006

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Geographic Projections

The structure of the succeeding words of the following geographic projections are listed here:

Lambert Conformal

If the type is LAMB, this is the structure of the succeeding words:

Word

Description

2

image line of the North Pole

3

image element of the North Pole

4

standard latitude 1, DDDMMSS

5

standard latitude 2, DDDMMSS

6

spacing at standard latitude, meters

7

normal longitude, DDDMMSS

8

radius of the planet, meters

9

eccentricity of the planet, x1000000

10

coordinate type, ≥ 0 planetodetic, < 0 planetocentric

11

longitude convention, ≥ 0 west positive, < 0 west negative

12-120

reserved

121-128

memo entry; up to 32 characters of comments

Mercator

If the type is MERC, this is the structure of the succeeding words:

Word

Description

2

image line of the equator

3

image element of the normal longitude

4

standard latitude, DDDMMSS; usually zero

5

spacing at standard latitude, meters

6

normal longitude, DDDMMSS

7

radius of the planet, meters

8

eccentricity of the planet, x1000000

9

coordinate type, ≥ 0 planetodetic, < 0 planetocentric

10

longitude convention, ≥ 0 west positive, < 0 west negative

11-120

reserved

121-128

memo entry; up to 32 characters of comments

Polar Stereographic

If the type is 'PS  ' (four characters), this is the structure of the succeeding words:

Word

Description

2

image line of the North Pole

3

image element of the North Pole

4

standard latitude, DDDMMSS

5

spacing at standard latitude, meters

6

normal longitude, DDDMMSS

7

radius of the planet, meters

8

eccentricity of the planet, x1000000

9

coordinate type, ≥ 0 planetodetic, < 0 planetocentric

10

longitude convention, ≥ 0 west positive, < 0 west negative

11-120

reserved

121-128

memo entry; up to 32 characters of comments

Radar

If the type is RADR, this is the structure of the succeeding words:

Word

Description

2

row (image coordinates) of the radar site

3

column (image coordinates) of the radar site

4

latitude of the radar site, DDDMMSS

5

longitude of the radar site, DDDMMSS

6

pixel resolution, meters

7

rotation of north from vertical, degrees x1000

8

if present, same as 6, but only for longitude direction

Rectilinear

If the type is RECT, this is the structure of the succeeding words:

Word

Description

2

a particular image row number

3

latitude corresponding to word 2, degrees x10000

4

a particular image column number

5

longitude corresponding to word 4, degrees x10000

6

latitude degrees/image line, degrees x10000

7

longitude degrees/image line, degrees x10000

8

radius of the planet, meters

9

eccentricity of the planet, x1000000

10

coordinate type, ≥ 0 planetodetic, < 0 planetocentric

11

longitude convention, ≥ 0 west positive, < 0 west negative

LALO (Latitude/Longitude)

If the type is LALO, this is the structure of the succeeding words:

Word

Description

2

SERV (indicates that the nav is coming from a server)

3-65

reserved

66

number of rows in LALO array

67

number of elements in LALO array

68

minimum latitude as a floating point number (in real*4 format) moved to the integer space

69

minimum longitude as a floating point number (in real*4 format) moved to the integer space

70

maximum latitude as a floating point number (in real*4 format) moved to the integer space

71

maximum longitude as a floating point number (in real*4 format) moved to the integer space

72

resolution of line lalo, 1 means there is latitude for every image line

73

resolution of element lalo, 1 means there is longitude for every image element

74

512 (size of NAV array)

75 word 74 + ((word 66)(word 67)(4))
76 line number in image coordinates of top line
77 element number in image coordinates of leftmost element
78 total size of LALO block
79 24 (size of latitude header)
80 offset in AUX to longitudes: word 79 + ((word 66)(word 67)(4)) + 28
81 offset in directory block to latitude block: 768 + word 79 + cal_length
82 offset in directory block to longitude block: word 81 + ((word 66)(word 67)(4)) + 28

83-128

reserved

 


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