I am not sure what you mean by a LM elevation map, but here is my proceedure or down loading a binary flat flle from the USGS web site to get a one degree by one degree map. For a specific example

Here I downloaded the map based on 1 arc sec. of resolution. In addition to the “.flt” and “.hdr” files, the picture file “jpg” file is useful. The picture file can be used to verify one has appropriately got the elevation map correct. The :.hdr” file contains the following information:

ncols 3612

nrows 3612

xllcorner -81.00166666667

yllcorner 38.99833333333

cellsize 0.000277777777778

NODATA_value -9999

byteorder LSBFIRST

The longitude and latitude of the lower left hand corner of the 1deg. by 1 deg. elevation map are given by xllcorner and yllcorner, respectively. Now set a variable Lon0=xllcorner and construct a vector for the longitude for n=1:ncols;lonvec(n)=Lon0+cellsize*(n-1);end The vector for the longitudes is straight forward, not so for the latitude vector. The data are indexed starting in the upper left-hand corner; whereas our lat-lon are indexed in the lower left-hand corner. This means to define our latitude vector in reverse order. Set a variable Lat0=yllcorner and construct a vector for the latitude for n=1:nrows;latvecinv(n)=Lat0+cellsize*nrows-cellsize*(n-1);end

Now read in the flat file for the elevations

fid=fopen(‘****.flt’,’r’) e

ev=fread(fid,inf,’real*4’);

elev=reshape(elev,ncols,nrows);

This should put the elevation map in the form elev(long,lat); however, we want x-axis to be pointing North, thus

elev=permute(elev,[2 1]);

This gives our elevation map in the form elev(lat,long). If we want to view our elevation map using MATLAB imagesc we need to understand that the normal way MATLAB indexes the array is like a matrix; i.e., (1,1) is in the upper left hand corner. However, we want to index our image starting in the lower left-hand corner. This is accomplished by using the call axis xy. Our call to imagesc is: imagesc(lonvec,latvecinv,elev);colorbar;axis xy;

To see if one has the map correct, compare to the jpg picture of the map given in the download.

Hope this helps

Lewis C. Bartel