diff --git a/rrlp-ephemeris/gps.h b/rrlp-ephemeris/gps.h
new file mode 100644
index 0000000..f6f7cc0
--- /dev/null
+++ b/rrlp-ephemeris/gps.h
@@ -0,0 +1,171 @@
+/*
+ * gps.h
+ *
+ * Header to deal with low level GPS data
+ *
+ *
+ * Copyright (C) 2009  Sylvain Munaut <tnt@246tNt.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GPS_H__
+#define __GPS_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+
+#define MAX_SV	64
+
+
+/* Ionosperic model data */
+struct gps_ionosphere_model {
+			/* #bits  Scale factor  Effective  Units            */
+			/*           (LSB)       range                      */
+
+	int alpha_0;	/* s 8       2^-30                 seconds          */
+	int alpha_1;	/* s 8       2^-27                 s / semi-circles */
+	int alpha_2;	/* s 8       2^-24                 s / (semi-circles)^2 */
+	int alpha_3;	/* s 8       2^-24                 s / (semi-circles)^3 */
+	int beta_0;	/* s 8       2^11                  seconds          */
+	int beta_1;	/* s 8       2^14                  s / semi-circles */
+	int beta_2;	/* s 8       2^16                  s / (semi-circles)^2 */
+	int beta_3;	/* s 8       2^16                  s / (semi-circles)^3 */
+};
+
+
+/* UTC model data */
+struct gps_utc_model {
+			/* #bits  Scale factor  Effective  Units            */
+			/*           (LSB)       range                      */
+
+	int a0;		/* s 32      2^-30                 seconds          */
+	int a1;		/* s 24      2^-50                 seconds / seconds */
+	int delta_t_ls;	/* s  8      1                     seconds          */
+	int t_ot;	/* u  8      2^12       602,112    seconds          */
+	int wn_t;	/* u  8      1                     weeks            */
+	int wn_lsf;	/* u  8      1                     weeks            */
+	int dn;		/* u  8      1                7    days             */
+	int delta_t_lsf;/* s  8      1                     seconds          */
+};
+
+
+/* Almanach data */
+struct gps_almanac_sv {
+	int sv_id;
+	int sv_health;
+
+			/* #bits  Scale factor  Effective  Units            */
+			/*           (LSB)       range                      */
+
+	int e;		/* u 16      2^-21                                  */
+	int t_oa;	/* u  8      2^12       602,112    seconds          */
+	int ksii;	/* s 16      2^-19                 semi-circles     */
+	int omega_dot;	/* s 16      2^-38                 semi-circles / s */
+	int a_powhalf;	/* u 24      2^-11                 meters           */
+	int omega_0;	/* s 24      2^-23                 semi-circles     */
+	int w;		/* s 24      2^-23                 semi-circles     */
+	int m_0;	/* s 24      2^-23                 semi-circles     */
+	int a_f0;	/* s 11      2^-20                 seconds          */
+	int a_f1;	/* s 11      2^-38                 seconds / seconds */
+};
+
+struct gps_almanac {
+	int wna;
+	int n_sv;
+	struct gps_almanac_sv svs[MAX_SV];
+};
+
+
+/* Ephemeris data */
+struct gps_ephemeris_sv {
+	int sv_id;
+
+			/* #bits  Scale factor  Effective  Units            */
+			/*           (LSB)       range                      */
+
+	int code_on_l2;	/* u  2      1                     /                */
+	int week_no;	/* u 10      1                     week             */
+	int l2_p_flag;	/* u  1      1                     /                */
+	int sv_ura;	/* u  4      /                     /                */
+	int sv_health;	/* u  6      /                     /                */
+	int t_gd;	/* s  8      2^-31                 seconds          */
+	int iodc;	/* u 10      /                     /                */
+	int t_oc;	/* u 16      2^4        604,784    seconds          */
+	int a_f2;	/* s  8      2^-55                 sec / sec^2      */
+	int a_f1;	/* s 16      2^-43                 sec / sec        */
+	int a_f0;	/* s 22      2^-31                 seconds          */
+
+	int c_rs;	/* s 16      2^-5                  meters           */
+	int delta_n;	/* s 16      2^-43                 semi-circles / s */
+	int m_0;		/* s 32      2^-31                 semi-circles     */
+	int c_uc;	/* s 16      2^-29                 radians          */
+	unsigned int e;	/* u 32      2^-33      0.03       /                */
+	int c_us;	/* s 16      2^-29                 radians          */
+	unsigned int a_powhalf; /* u 32  2^-19             meters^(1/2)     */
+	int t_oe;	/* u 16      2^4        604,784    seconds          */
+	int fit_flag;	/* u  1      /                     /                */
+
+	int c_ic;	/* s 16      2^-29                 radians          */
+	int omega_0;	/* s 32      2^-31                 semi-circles     */
+	int c_is;	/* s 16      2^-29                 radians          */
+	int i_0;	/* s 32      2^-31                 semi-circles     */
+	int c_rc;	/* s 16      2^-5                  meters           */
+	int w;		/* s 32      2^-31                 semi-circles     */
+	int omega_dot;	/* s 24      2^-43                 semi-circles / s */
+	int idot;	/* s 14      2^-43                 semi-circles / s */
+
+	int _rsvd1;	/* 23 bits */
+	int _rsvd2;	/* 24 bits */
+	int _rsvd3;	/* 24 bits */
+	int _rsvd4;	/* 16 bits */
+	int aodo;	/* 8 bits  Not sure it needs to be here ... */
+};
+
+struct gps_ephemeris {
+	int n_sv;
+	struct gps_ephemeris_sv svs[MAX_SV];
+};
+
+
+/* All assist data */
+#define GPS_FIELD_IONOSPHERE	(1<<0)
+#define GPS_FIELD_UTC		(1<<1)
+#define GPS_FIELD_ALMANAC	(1<<2)
+#define GPS_FIELD_EPHEMERIS	(1<<3)
+
+struct gps_assist_data {
+	int fields;
+	struct gps_ionosphere_model	ionosphere;
+	struct gps_utc_model		utc;
+	struct gps_almanac		almanac;
+	struct gps_ephemeris		ephemeris;
+};
+
+
+/* GPS Subframe utility methods (see gps.c for details) */
+int gps_unpack_sf123(uint32_t *sf, struct gps_ephemeris_sv *eph);
+int gps_unpack_sf45_almanac(uint32_t *sf, struct gps_almanac_sv *alm);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __GPS_H__ */
+