GRID-file: get max extent for all z-values above given value

Question

I have a GRID-file with a quite large extent. For an automatic workflow I need the maximum extent/bounding-box for all z-values that are over a certain range. For example: Get the maximum extent for all z-values that are greater or equal than 0.05

Is there a possibility to do that with Python, GDAL or GMT-tools (generic mapping tools), so that it can run automatically?

Answer 1

not the best solution but solved the problem for me. For anybody who wants to know how I did it:

gdal_contour -i 1000 -off 0.05 input.grd output.shp

-i = some very high number -off = minimum pixel value

then:

ogrinfo -al -so output.shp

and parse the ogrinfo output to get the extent coords

EDIT Better Solution (Python3 with Subprocess):

gdal_calc.py -A input.grd --oufile=temp.tif --calc=logical_an(A>=min, A<=max)
gdal_polygonize.py temp.tif -f GMT temp.gmt

with Python3:

gmt_file = open(temp.gmt)
extent_temp = gmt_file.readlines[1]
extent = re.findall("(-?\d+.\d+)",extent_temp)

west = extent_w_time[0]   
east = extent_w_time[1]   
south = extent_w_time[2]   
north = extent_w_time[3]