[GIS] How to get latitude, longitude and altitude database from a GeoTIFF file

altitudeccoordinatesgeotiff-tiff

I am developing an AR iOS application. When the iPhone gets the current location, it has to calculate locally the visible point. I want to read the tiff files in my application, and then get the coordinates and altitudes from it.(locally, offline) I am looking for an open source C++ code, or something like this. Please help

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With libtiff you can't get altitude from you file. I spent a lot of time trying to do it with libgeotiff. My advice is to install GDAL.

Example:

GDALRasterIO( hBand_ , GF_Read , p, l, 1, 1, &pafScanline, 1, 1, GDT_Float32, 0, 0 );

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[GIS] Latitude – Longitude bounds from GeoTIFF info

Sure,

Firstly, open it in QGIS, and then in the menu at the top go to Raster->Miscellaneous->Information.

Select the layer in the "Input-file" drop-down box (if it's not already there) then press OK, and it will create a load of text relating to information about the layer in a box called "Raster Info".

If you scroll down this text, you will get to a line that says "Corner Coordinates", the following 4 lines look like this:

Upper Right ( 5486108.843, 5015161.555) ( 14d49'22.49"E, 45d16'51.06"N)

and describe the coordinates of each corner (the geographic bounds) (in my example, given as both projected and geographic coordinates).

Is that what you're after?

Note: if you can't see any part of Raster->Miscellaneous->Information in the menu, go to Plugins->Manage and Install Plugins, and make sure that the box next to "GDAL Tools" is ticked, this will make it appear

[GIS] How to get long, lat and altitude info from geotiff file using GDAL and C++

I'm not sure what you mean by "for each pixel". look at the raster API tutorial: http://gdal.org/gdal_tutorial.html. specifically look at the section "Getting Dataset Information".

do you want to get the information that gets dumped by the gdalinfo tool? that is easy. the gdalinfo tool source code comes-with the source download. just get it and look at it. very easy to understand.

Now I see the "altitude" part. Duh.

The raster (pixels) are numbers which are the altitudes. if you know the pixel row/col, it is relatively easy to get the lat/lon/alt. look at the source for gdallocationinfo. it will show you how to take coordinates and look up the pixel. You'd do the same thing, but you don't need to convert from coordinates to pixel since you're starting with pixel coordinate. then you want to convert the pixel to coordinates in some SRS. look at gdaltransform for that.

Also the tutorials. The raster API tutorial (http://gdal.org/gdal_tutorial.html) will show you how to open the tif and read the altitude. Then you use the inverse of the geo transform to convert the pixel row/col to the coordinates in the TIF's SRS. The tutorial will also show you how to get the SRS for the tif.

The TIF SRS may not be geodetic coordinates, or not in the datum you wish. If that is the case, the OGR tutorial (http://gdal.org/gdal_tutorial.html) will show you how to convert coordinates from the TIF's SRS to the one you want (e.g. WGS84).

I cannot stress enough that the tutorials and source code for the GDAL raster utilities are your friend. All that you're asking to do has been implemented in those utilities, which are simple and very well written.

-reilly.

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[GIS] Latitude – Longitude bounds from GeoTIFF info

[GIS] How to get long, lat and altitude info from geotiff file using GDAL and C++

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