Geoscience Reference
In-Depth Information
ans =
1504
In our example the maximum elevation of the area is 3,992 m above sea level
and the minimum is 1,504 m. A coordinate system can be dei ned using
the information that the lower-let corner is
s01e036
. h e resolution is 3 arc
seconds, corresponding to 1/1,200 of a degree.
[LON,LAT] = meshgrid(36:1/1200:37,-1:1/1200:0);
A shaded grayscale map can be generated from the elevation data using
the function
surfl
. h is function displays a shaded surface with simulated
lighting.
surfl(LON,LAT,SRTM)
shading interp
colormap gray
view(0,90)
h is script opens a new i gure window and generates the shaded-relief
map using interpolated shading, as well as a gray colormap, displayed in an
overhead view. Since SRTM data contain a large amount of noise, we i rst
smooth the data using an arbitrary 9-by-9 pixel moving average i lter. h e
new matrix is then stored in the matrix
SRTM_FILTERED
.
B = 1/81 * ones(9,9);
SRTM_FILTERED = filter2(B,SRTM);
h e corresponding shaded-relief map is generated by
surfl(LON,LAT,SRTM_FILTERED)
shading interp
colormap gray
view(0,90)
At er having generated the shaded-relief map (Fig. 7.4), the plot must be
exported to a graphics i le. For instance, the i gure may be written into a
JPEG format with a 70% quality level and 300 dpi resolution.
Interactive
7.3
print -djpeg70 -r300 srtmimage
h e new i le
srtmimage.jpg
has a size of 320 KB; the decompressed image
has a size of 16.5 MB. h is i le can now be imported into another sot ware
package such as Adobe Photoshop.
