Based on the gps receiver from hab supplies, the work of jgilje and debian jessie I have been able to compile a minimal image which can work as a Stratum-1 ntp server.

The image itself is ~90MB compressed, and contains a minimal installation of debian jessie, kernel from hardkernel with the pps-gpio patch from jgilje. ntp package was recompiled and is held from future updates. ntpd is preconfigured to use NMEA(127.127.20.0) driver with PPS sync. And udev rules to create the apropriate devices for ntpd to use. I also removed all of the dvb drivers in the kernel provided by hardkernel.

If you want to relocate the PPS signal to a different gpio pin, this can be done by altering the meson8b_odroidc.dts file and compiling it to an apropriate .dtb file.

Image can be written to memory card using win32diskimager or dd, it will use dhcp for network configuration. Only user enabled is root with the password root. Framebuffer should also work, so you can connect it to a screen and configure it locally.

Things to do at first boot. Use fdisk to delete partition 2, and recreate the partition with the same size as the sd-card. Then resize the root partition.

Please note that on cold boot, it will take some time to lock onto the PPS.

Sources:
https://github.com/jgilje/pps-gpio-amlogic
http://ava.upuaut.net/store/index.php?route=product/product&path=59_60&product_id=117

Download:
odroidc1.img

Some ntpd output.


root@odroid-c1:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+ntp.fnutt.net 192.36.134.17 2 u 5 64 377 11.512 0.230 0.812
+2.81-166-42.cus 85.89.3.25 2 u 36 64 377 4.607 -0.430 0.612
+langbein.monslo 129.242.4.241 2 u 40 64 377 15.449 -1.063 0.953
-ntp-ext.cosng.n 146.213.3.181 2 u 24 64 377 14.528 1.604 1.253
oGPS_NMEA(0) .GPS. 0 l 12 16 377 0.000 -0.001 0.001


root@odroid-c1:~# ntpq -c rl
associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync,
version="ntpd 4.2.6p5@1.2349-o Mon May 25 18:52:44 UTC 2015 (1)",
processor="armv7l", system="Linux/3.10.75", leap=00, stratum=1,
precision=-20, rootdelay=0.000, rootdisp=0.354, refid=GPS,
reftime=d90ed892.9bbc5b1d Tue, May 26 2015 11:33:38.608,
clock=d90ed89b.4cfcafe8 Tue, May 26 2015 11:33:47.300, peer=59860, tc=4,
mintc=3, offset=-0.001, frequency=9.542, sys_jitter=0.001,
clk_jitter=0.001, clk_wander=0.000