landsat 7 natural colors

Landsat Natural Colors

Using Global Mapper 11 & Photoshop CS3

Spring 2010

C.D.G.

2

Using Global Mapper 11 and Photoshop CS3

Landsat natural color

The main difficulty of producing a fairly natural color Landsat image is to keep the high resolution (14.25m) of the panchromatic layer without distorting it on pixel level by overlaying the lower (28.5m) resolution of the 3 visible layers of Red, Green, Blue. The other difficulty is the natural skyhaze that distorts visible data according to the specific atmospheric conditions of the given moment of the satellite shot. And the last difficulty is the various differentiantions between the tiles, due to the aforementioned factor. I describe here a method that has given good results. -

C.D.G.

3

Collecting Data pages 4-11

Processing Data in Global Mapper

pages 12-19

Correcting colors in Photoshop pages 20-30

a very basic knowledge of Global Mapper, Photoshop and GIS concepts is required

4

we start our search for

Landsat data by heading to the

right tool

we select path and row for our Area of interest

(AoI)

http://landsat.usgs.gov/tools_latlong.php

5Obtaining the needed data (path) ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2/

we then head for the actual

data site

we select the path

6Obtaining the needed data (row) ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2/

we select the row

7Obtaining the needed data (specifically) ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2/

we select : ETM-Earthsat-Orthorectified

or ETM-Earthsat-

GLS2000

8Obtaining the needed data (file 1) ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2/

we select : ...80.tif.gz

it is the panchromatic

high resolu-tion file

9


it is a black & white file

which collects the sensible in red spectrum

Obtaining the needed data (file 2) ftp://ftp.glcf.umiacs.umd.edu/glcf/Landsat/WRS2/

10


it is a black & white file

which collects the sensible in

green spectrum


11


it is a black & white file which

collects the sensible in blue

spectrum


12

Changing Projection (from UTM)

after opening all the files in

Global Mapper: we proceed

to the Tools > Configure > Projection

and change the UTM projec-tion to the

Geographic (Latitude/Longi-

tude).

in Global Mapper

13

Changing Projection (to Geographic)

we specify our chosen Geographic Projection

[we change the projection to Geographic if

we have to deal with a number

of different zone files]

in Global Mapper

14

we keep visible all ...80.tif.gz of our area of

interest

we set RGP(0,0,0) as transparent color, as we

want to get rid of the black collar of the

tile(s)

[if we have more than 1 tile, we try to render their color in-

tensity as close as possible. This is needed only

for the ...80 files]

in Global Mapper

15

[we will continue with an example -a small area- for the rest of the

procedure]

in Global Mapper

16

we create tile(s) for our AoI

in Global Mapper

17

in exporting options, we choose the

export bounds to be cropped to the selected

area(s)

in Global Mapper

18

and we export as e.g. 80.tif,

generating also its tfw file

in Global Mapper

19

we repeat the above steps (hiding and showing accordingly)

3 more times for ...30.tif.gz, ...20.tif.gz

and ...10.tif.gz saving as e.g. 30.tif, 20.tif and 10.tif

no need for tfw files here

in Global Mapper

20

we open in Photoshop

80.tif, 30.tif, 20.tif and 10.tif

we select all

30.tif and copy

in Photoshop

21

we create a new but RGB file

we flatten image

we select the

red channel and paste

we repeat

“select all, copy and paste”

respectively in green channel

for 20.tif and in blue for 10.tif

in Photoshop

22

we select the RGB channel

in Photoshop

23

we autolevel

colors

in Photoshop

24

we resize the image as the image size of

80.tif and save it as 321.tif

in Photoshop

25

we select all 80.tif and copy

we paste the 80 layer setting its blending mode

at luminosity over the com-

posite 321 layer

we merge visible layers and save as

80.tif

in Photoshop

26

we select Image > Adjustments > Match Color and

set as Source Image the

321.tif

in Photoshop

27

we adjust: Brightness -20 Contrast +20

(or according to our taste...)

in Photoshop

28

last step is to select (magic wand) the sea area and fill it with a consis-

tent color

(it doesn’t look so bad in our

example, but it is a big problem when working

with larger areas and much worse with many Land-

sat tiles)

in Photoshopin Photoshop

29

we save as 80.tif

in Photoshop

30Finished !

as we kept the same name

(80.tif ) for our file with its

relevant 80.tfw file, it is still

georeferenced (Geographic Projection,

WGS84 Datum) if opened in GM

as an illustration of the results of the afore-

mentioned process with a multi-tiled Landsat

area, the links to the right point to 4 georefer-

enced pdf tiles for the island of Crete in Greece

derived out of 4 Landsat 7 GLS2000 tiles

these pdf files may be opened in Acrobat

9 Pro Extended and extracted as JPEG2000

(jp2) image files, then imported back in Global

Mapper 11 (georeferenced pdf of Acrobat are

not readable as such by GM)

exporting them as geopdf files via GM pro-

duced an undesired crosshair grid, hence they

were initially exported from GM as JPEG2000

and imported in Acrobat 9

1 of 4 tiles: http://www.scribd.com/doc/29026342/Crete-West-Landsat-7-ETM 2 of 4 tiles: http://www.scribd.com/doc/29025501/Crete-East-Landsat-7-ETM

3 of 4 tiles: http://www.scribd.com/doc/29026066/Crete-East-Central-Landsat-7-ETM

4 of 4 tiles: http://www.scribd.com/doc/29026859/Crete-West-Central-Landsat-7-ETM

a vision

“...All spatial data collected with federal funds must be made available to the

public at the cost of distribution, without copyright restrictions...”

President of the USA Clinton, 1994

a dream

“All spatial data collected and/or pro-cessed with public funds must be made available to the public at the cost of dis-tribution, without copyright restrictions.

Only spatial data unavailable through

private organizations may be considered as of military interest and thus remain

unaccessible to the public for the duration of the above provision”

C.D.G.

Spring 2010

C.D.G.

NASA Landsat Program

U.S.

Geological Survey

University of Maryland

University

of California San Diego

Thanks to:

landsat 7 natural colors

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