Current (3.17) gpsprof is broken:

$  gpsprof > foo.gpt
   correctly generates a gnuplot file with 100 samples.


$ gpsprof -l foo.log > foo.gpt
gpsprof: replotting......(0.01 sec) done.
Traceback (most recent call last):
  File "/usr/bin/gpsprof", line 529, in <module>
    plot.postprocess()
  File "/usr/bin/gpsprof", line 206, in postprocess
    self.centroid = (sum([x[0] for x in self.fixes]) / len(self.fixes),
ZeroDivisionError: division by zero

rewinding to 3.16 has a different, but also fatal breakage, in that all positions read from the logfile are recorded as 0 or nan:

plot "-" using 1:2 with points ls 3 title "101 GPS fixes" , cx(t, cep),cy(t, cep) ls 1 title "CEP (50%) = 0.000000 meters", cx(t, cep95),cy(t, cep95) title "CEP (95%) = 0.000000 meters", cx(t, cep99),cy(t, cep99) title "CEP (99%) = 0.0000
00 meters"
# Position uncertainty, 2018-03-02T23:14:16, u-blox, 9600 8N1, cycle 1s
0.000000        0.000000        0.000000        0.000000        nan
0.000000        0.000000        0.000000        0.000000        nan
0.000000        0.000000        0.000000        0.000000        nan
0.000000        0.000000        0.000000        0.000000        nan
0.000000        0.000000        0.000000        0.000000        nan
0


The total effect is that no offline plots can be generated.