MATLAB: Georeferencing

georeferencing image map .tfwMapping Toolbox

Hi all I have an image; the Trimmed satellite image with Latitude and longitude coordinates from here:

http://www.maplibrary.org/stacks/Africa/Kenya/index.php

It comes with a .tfw file. (6 x 1).

How on Earth do I use the .tfw file to assign coordinates to each pixel? I have just got the mapping toolbox. Thanks

Best Answer

You can use worldfileread to read the data into a referencing matrix, which can then be used to calculate coordinates for any pixel in the image.

 doc worldfileread
 doc pix2map

If you just want to display the image, though, geoshow and mapshow handle tif/tfw paired files.

 tiffile = 'KEN_satellite_trimmed.tif';
 geoshow(tiffile);

Related Solutions

MATLAB: How can we find the non common strings from multiple columns

First lets find the strings that are common to all cell arrays:

listA={'India','Iran','Ireland','Israel','Jordan','Kuwait','Lebanon','Lesotho','Libya','Luxembourg','Malawi','Maldives','Morocco','Nepal','Netherlands','Norway','Oman','Paraguay','Peru','Philippines',};
listB={'Denmark','El Salvador','Gabon','Gambia','Lebanon','Lesotho','Libya','Luxembourg','Malawi','Maldives','Morocco','Nepal','Netherlands','Norway','Oman','Paraguay','Peru','Philippines','Qatar','Rwanda','Saudi Arabia','Senegal','Singapore','Sudan'};
listC={'Kuwait','Lebanon','Lesotho','Nepal','Netherlands','Oman','Sweden','Syria','Tanzania','Turkey','Uruguay'};
%

lists = {listA,listB,listC}; % storing data together makes working with them much simpler.
%
exc = lists{1};
for k = 2:numel(lists)
    exc = intersect(exc,lists{k});
end

giving the strings found in all cell arrays as:

 exc =
    'Lebanon'
    'Lesotho'
    'Nepal'
    'Netherlands'
    'Oman'

Now we can easily get the input cell arrays with the strings from exc removed:

out = cell(size(lists));
for k = 1:numel(lists)
    out{k} = setdiff(lists{k},exc);
end

giving:

>> out{:}
ans = 
    'India' 'Iran' 'Ireland' 'Israel' 'Jordan' 'Kuwait' 'Libya' 'Luxembourg' 'Malawi' 'Maldives' 'Morocco' 'Norway' 'Paraguay' 'Peru' 'Philippines'
ans =
    'Denmark' 'El Salvador' 'Gabon' 'Gambia' 'Libya' 'Luxembourg' 'Malawi' 'Maldives' 'Morocco' 'Norway' 'Paraguay' 'Peru' 'Philippines' 'Qatar' 'Rwanda' 'Saudi Arabia' 'Senegal' 'Singapore' 'Sudan'
ans =
    'Kuwait' 'Sweden' 'Syria' 'Tanzania' 'Turkey' 'Uruguay'

And if you want a list of all strings together, excluding those in exc:

uni = {};
for k = 1:numel(lists)
    uni = union(uni,lists{k});
end
uni = setdiff(uni,exc)

gives:

uni =
    'Denmark' 'El Salvador' 'Gabon' 'Gambia' 'India' 'Iran' 'Ireland' 'Israel' 'Jordan' 'Kuwait' 'Libya' 'Luxembourg' 'Malawi' 'Maldives' 'Morocco' 'Norway' 'Paraguay' 'Peru' 'Philippines' 'Qatar' 'Rwanda' 'Saudi Arabia' 'Senegal' 'Singapore' 'Sudan' 'Sweden' 'Syria' 'Tanzania' 'Turkey' 'Uruguay'

MATLAB: Must I change the geoid using UTM projection

In order to work with Google Earth, you should specify the WGS 84 ellipsoid in your code by replacing lines 4 and 5 with:

    utmstruct.geoid = almanac('earth','wgs84','meters');

if you are working in meters, or:

    utmstruct.geoid = almanac('earth','wgs84','kilometers');

if you are working in kilometers, etc.

UTM was designed in the first half of the 20th century, well before artificial satellites made a global system like WGS 84 possible. So different local datums (and their ellipsoids) were used for UTM in different parts of the world. The purpose of the utmgeoid function is to do a geographic look-up of the standard ellipsoid for a given zone. But now UTM is used with datums like NAD 83 and WGS 84, which did not exist when it was originally defined. The utmgeoid function is not relevant in such cases.

The statement in the solution, "MATLAB’s default reference ellipsoid is International, not WGS 84" is misleading. It really should say something like: "defaultm uses the International ellipsoid for UTM when the ellipsoid and zone unspecified." (The International ellipsoid is the default only in this context.)

Best Answer

Related Solutions

MATLAB: How can we find the non common strings from multiple columns

MATLAB: Must I change the geoid using UTM projection

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