This is the command Planimeter that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

**PROGRAM:**

**NAME**

Planimeter -- compute the area of geodesic polygons

**SYNOPSIS**

**Planimeter**[

**-r**] [

**-s**] [

**-l**] [

**-e**

__a__

__f__] [

**-w**] [

**-p**

__prec__] [

**-G**|

**-E**|

**-Q**|

**-R**] [

**--comment-delimiter**

__commentdelim__] [

**--version**|

**-h**|

**--help**] [

**--input-file**

__infile__|

**--input-string**

__instring__] [

**--line-separator**

__linesep__] [

**--output-file**

__outfile__]

**DESCRIPTION**

Measure the area of a geodesic polygon. Reads polygon vertices from standard input, one

per line. Vertices may be given as latitude and longitude, UTM/UPS, or MGRS coordinates,

interpreted in the same way as

__GeoConvert__(1). (MGRS coordinates signify the center of the

corresponding MGRS square.) The end of input, a blank line, or a line which can't be

interpreted as a vertex signals the end of one polygon and the start of the next. For

each polygon print a summary line with the number of points, the perimeter (in meters),

and the area (in meters^2).

The edges of the polygon are given by the

__shortest__geodesic between consecutive vertices.

In certain cases, there may be two or many such shortest geodesics, and in that case, the

polygon is not uniquely specified by its vertices. This only happens with very long edges

(for the WGS84 ellipsoid, any edge shorter than 19970 km is uniquely specified by its end

points). In such cases, insert an additional vertex near the middle of the long edge to

define the boundary of the polygon.

By default, polygons traversed in a counter-clockwise direction return a positive area and

those traversed in a clockwise direction return a negative area. This sign convention is

reversed if the

**-r**option is given.

Of course, encircling an area in the clockwise direction is equivalent to encircling the

rest of the ellipsoid in the counter-clockwise direction. The default interpretation used

by

**Planimeter**is the one that results in a smaller magnitude of area; i.e., the magnitude

of the area is less than or equal to one half the total area of the ellipsoid. If the

**-s**

option is given, then the interpretation used is the one that results in a positive area;

i.e., the area is positive and less than the total area of the ellipsoid.

Only simple (i.e., non-self-intersecting) polygons are supported for the area computation.

Polygons may include one or both poles. There is no need to close the polygon.

**OPTIONS**

**-r**toggle whether counter-clockwise traversal of the polygon returns a positive (the

default) or negative result.

**-s**toggle whether to return a signed result (the default) or not.

**-l**toggle whether the vertices represent a polygon (the default) or a polyline. For a

polyline, the number of points and the length of the path joining them is returned;

the path is not closed and the area is not reported.

**-e**specify the ellipsoid via

__a__

__f__; the equatorial radius is

__a__and the flattening is

__f__.

Setting

__f__= 0 results in a sphere. Specify

__f__< 0 for a prolate ellipsoid. A simple

fraction, e.g., 1/297, is allowed for

__f__. By default, the WGS84 ellipsoid is used,

__a__=

6378137 m,

__f__= 1/298.257223563. If entering vertices as UTM/UPS or MGRS coordinates,

use the default ellipsoid, since the conversion of these coordinates to latitude and

longitude always uses the WGS84 parameters.

**-w**when reading geographic coordinates, longitude precedes latitude (this can be

overridden by a hemisphere designator,

__N__,

__S__,

__E__,

__W__).

**-p**set the output precision to

__prec__(default 6); the perimeter is given (in meters) with

__prec__digits after the decimal point; the area is given (in meters^2) with (

__prec__- 5)

digits after the decimal point.

**-G**use the series formulation for the geodesics. This is the default option and is

recommended for terrestrial applications. This option,

**-G**, and the following three

options,

**-E**,

**-Q**, and

**-R**, are mutually exclusive.

**-E**use "exact" algorithms (based on elliptic integrals) for the geodesic calculations.

These are more accurate than the (default) series expansions for |

__f__| > 0.02. (But

note that the implementation of areas in GeodesicExact uses a high order series and

this is only accurate for modest flattenings.)

**-Q**perform the calculation on the authalic sphere. The area calculation is accurate even

if the flattening is large,

__provided__the edges are sufficiently short. The perimeter

calculation is not accurate.

**-R**The lines joining the vertices are rhumb lines instead of geodesics.

**--comment-delimiter**

set the comment delimiter to

__commentdelim__(e.g., "#" or "//"). If set, the input

lines will be scanned for this delimiter and, if found, the delimiter and the rest of

the line will be removed prior to processing. For a given polygon, the last such

string found will be appended to the output line (separated by a space).

**--version**

print version and exit.

**-h**print usage and exit.

**--help**

print full documentation and exit.

**--input-file**

read input from the file

__infile__instead of from standard input; a file name of "-"

stands for standard input.

**--input-string**

read input from the string

__instring__instead of from standard input. All occurrences

of the line separator character (default is a semicolon) in

__instring__are converted to

newlines before the reading begins.

**--line-separator**

set the line separator character to

__linesep__. By default this is a semicolon.

**--output-file**

write output to the file

__outfile__instead of to standard output; a file name of "-"

stands for standard output.

**EXAMPLES**

Example (the area of the 100km MGRS square 18SWK)

Planimeter <<EOF

18n 500000 4400000

18n 600000 4400000

18n 600000 4500000

18n 500000 4500000

EOF

=> 4 400139.53295860 10007388597.1913

The following code takes the output from gdalinfo and reports the area covered by the data

(assuming the edges of the image are geodesics).

#! /bin/sh

egrep '^((Upper|Lower) (Left|Right)|Center) ' |

sed -e 's/d /d/g' -e "s/' /'/g" | tr -s '(),\r\t' ' ' | awk '{

if ($1 $2 == "UpperLeft")

ul = $6 " " $5;

else if ($1 $2 == "LowerLeft")

ll = $6 " " $5;

else if ($1 $2 == "UpperRight")

ur = $6 " " $5;

else if ($1 $2 == "LowerRight")

lr = $6 " " $5;

else if ($1 == "Center") {

printf "%s\n%s\n%s\n%s\n\n", ul, ll, lr, ur;

ul = ll = ur = lr = "";

}

}

' | Planimeter | cut -f3 -d' '

Use Planimeter online using onworks.net services