generic mapping tools

7/28/2019 Generic Mapping tools

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Introduction to GMT(Generic Mapping Tools)

Lab 9


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What is GMT?

A mapping tool commonly used by geophysicists formanipulating and visualizing data

Free!Has a steep learning curve, but worth the climb Available from http://gmt.soest.hawaii.eduin a number of flavorsThere are other programs that will do the same sort of thing,but none have the same flexibility


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GMT Example Maps


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pscoast -JA0/20/2.5i -R0/360/-90/90 -Bg30/g15:.Global Map:

-Dl -G187/142/46 -S109/202/255 -N1 -P > simple_globe.ps

Map projection Map re

gionBasemap info (boundaries, grids spacing, title)

Data

resolution Land colorWater color

National

Boundaries Portrait layout Map file

name


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Map projection Map re

gionBasemap info (boundaries, grids spacing, title)

Data


Portrait layout Map file

name

-JA0/20/2.5i

Center Longitude = 0

Center Latitude = 20

Width = 2.5 (or 5) inches

Lambert Azimuthal projection

National

Boundaries


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Map projection Map regionBasemap info (boundaries, grids spacing, title)

Data



name

Max. Longitude

Min. latitudeMax. latitude

Min. Longitude

-R0/360/-90/90

National

Boundaries


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Data



name

grid spacing (latitude)

Map titlegrid spacing (longitude)

-Bg30/g15:.Global Map:

National

Boundaries


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Data


Portrait layout Map filename

l = low resolution data

-Dl

National

Boundaries


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Data


Portrait layout Map filename

Green

BlueRed

-G187/142/46

National

Boundaries


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RGB Colors

Range from 0 (little) - 255 (lot)


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Data


National

Boundaries Portrait layout Map filename

Green

BlueRed

-S109/202/255


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Data


National


1 = national boundaries

-N1 1 = National boundaries2 = State boundaries within the Americas

3 = Marine boundariesa = All boundaries (1-3)


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Data


National



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Lab 9 Part 1: Annotated Map

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pscoast -Jb-154/50/55/65/1:21000000 -R172/230/51/72

-B10g5/5g5 -W1p/0/0/0 -P -Ia/2p/0/192/255 -G220/220/220

-S0/192/255 -L210/54/54/1000 -N1/1p/0/0/0 > alaska_map.ps

Map projectionMap region

Basemap

Water color LandcolorNationalBoundaries


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pscoast -Jb-154/50/55/65/1:21000000 -R172/230/51/72

-B10g5/5g5 -W1p/0/0/0 -P -Ia/2p/0/192/255 -G220/220/220


Draw coastlines

-W1p/0/0/0

Pen width = 1point

RGB color (black)


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pscoast -Jb-154/50/55/65/1:21000000 -R172/230/51/72

-B10g5/5g5 -W1p/0/0/0 -P -Ia/2p/0/192/255 -G220/220/220


Draw rivers

-Ia/2p/0/192/255

RGB color (blue)

Pen width = 1point

draw all rivers


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pscoast -Jb-154/50/55/65/1:21000000 -R172/230/51/72

-B10g5/5g5 -W1p/0/0/0 -P -Ia/2p/0/192/255 -G220/220/220


Draw a map scale

-L210/54/54/1000

Calculation

(lat.) location

Origin lat.Origin long.

Scale Bar (-L)

A scale bar can easily be added to the map using the -L

switch. To create the scale bar we need the latitude andlongitude of the point where we want to place it. Since

scale varies as we move further from the equator, we

also specify the latitude at which we want the scale

calculated. Lastly we indicate the length the scale bar

should span. The default is kilometers but you canappend m for miles or n for nautical miles. Putting it all

together we have -L210/54/54/1000 which gives a

1,000 km scale bar calculated at 54 degrees northlatitude and originating at 210 degrees longitude and 54

degrees latitude.

Length

(km)

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