[gdal-dev] Help with GeoData

Barry Hollran barry at pocket-link.com
Sat Aug 23 14:57:03 EDT 2008

Hi All,

I am very new to geo data and need some help.

I will try and explain what I have and where I need to get to. I have
developed some custom software that reads in Google Map files. These are
organised in layers 0 - 20 with each image being a jpg file. Each file is
256 x 256 pipels in size. This software works OK at the moment. The data
that I am using is downloaded from google maps as I have only needed small
test datasets up until now. 

I have purchased a data set of Portugal which I have in 2 Formats (Mapinfo
and Arcview), I have choosen to use the Mapinfo data set. This has 8 Layers.
and is split into much larger tiles. i.e 6000ish by 6000ish pixels.

In short I need to convert all the mapinfo data to a google style dataset so
that the existing software can use it. I would also like to (if possible use
Mapserver to serve the new data so that I can store only the bits I need off

Where I am now.

I have downloaded and installed GDAL and FWTools. 

using gdalinfo and ogrinfo for both data sets as well as google searches 

I think that the google data uses the wsg84 datum in  mercator projection.
(This does not mean a lot to me but I have read up as much as I can)

I think the Mapinfo data uses the wsg84 datum and a Lambert Conical

the Mpainfo tab file is:

!version 300
!charset WindowsLatin1

Definition Table
File "8000000.TIF"
(0,0) (0,2304) Label "Pt 1",
(0,7558272) (0,0) Label "Pt 2",
(7558272,7558272) (2304,0) Label "Pt 3",
(7558272,0) (2304,2304) Label "Pt 4"
CoordSys Earth Projection 3, 104, "m", 5, 49.08516574, 44, 54, 1507373,
Units "m"

And using gdalinfo i get the following:

Driver: GTiff/GeoTIFF
Files: 8000000.tif
Size is 2304, 2304
Coordinate System is `'
Origin = (0.000000000000000,7558272.000000000000000)
Pixel Size = (3280.500000000000000,-3280.500000000000000)
Image Structure Metadata:
Corner Coordinates:
Upper Left  (       0.000, 7558272.000) 
Lower Left  (   0.0000000,   0.0000000) 
Upper Right ( 7558272.000, 7558272.000) 
Lower Right ( 7558272.000,       0.000) 
Center      ( 3779136.000, 3779136.000) 
Band 1 Block=2304x8 Type=Byte, ColorInterp=Palette
  Image Structure Metadata:
  Color Table (RGB with 16 entries)
    0: 0,0,0,255
    1: 36,36,36,255
    2: 84,84,84,255
    3: 128,128,128,255
    4: 168,168,168,255
    5: 255,255,255,255
    6: 0,0,255,255
    7: 112,189,217,255
    8: 140,176,135,255
    9: 168,196,151,255
   10: 196,214,171,255
   11: 199,191,209,255
   12: 247,181,102,255
   13: 255,0,0,255
   14: 255,255,0,255
   15: 255,255,140,255

I have uploaded the tif file if it helps!

I have played with cs2cs to try and change the projection so that it would
be the same a s the google one(I dont even know if I need to do this, but
was experimenting)

If I under stand the above correctly the tif is 2304 pixels wide and each
pixel represents 3280.5 meters wide, so this tif represents a total size in
metrs of 7558272 wide, as can be seen in the top left size etc. But where is
this referenced from? I think I need to make sure that booth the google data
and mapinfo data are referenced from the same place.

Can any one please tell me the best way to try and acheive this?

A breakdown of steps would be great, and a confirmation of my understading
so far would also help.

Many thanks in advance.


http://n2.nabble.com/file/n778740/8000000.tif 8000000.tif 
http://n2.nabble.com/file/n778740/8000000.TAB 8000000.TAB 
View this message in context: http://n2.nabble.com/Help-with-GeoData-tp778740p778740.html
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