[gdal-dev] New user query about OGR library NTF import

A.J. Carter ajc200 at maths.leeds.ac.uk
Sat Nov 14 13:10:55 EST 2009


I was hoping someone might be able to help me with a query about using the 
OGR library to read an Ordnance Survey Landform Profile file in NTf format:


The file contains a 501 X 501 grid with height values at each point. From 
the technical reference on the OS web page it lists this as being stored 
within a field called Z_COORD. Manually inspecting the NTF file (which is 
plain text) I can see values like 00159 meaning 15.9m AOD. If I run the 
NTF through OGRINFO -al on the file produces a feature for this point:

   HEIGHT (Integer) = 15
   POINT (310000.0 490000.0 15.899999618530273)

At the moment I can't understand why it's writing out the height as an 
integer, and also where the many decimal places in the z coordinate of the 
point have come from.

Any help would be much appreciated.

I'm relatively new to GIS software; sorry if this is a silly question!

Many thanks,

More information about the gdal-dev mailing list