diff --git a/include/Makefile.am b/include/Makefile.am
index a6341f1a3..fc1eec33a 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -92,6 +92,7 @@ nobase_include_HEADERS = \
                        osmocom/coding/gsm0503_interleaving.h \
                        osmocom/coding/gsm0503_coding.h \
                        osmocom/coding/gsm0503_amr_dtx.h \
+                       osmocom/gsm/gad.h \
                        osmocom/gsm/gsm0808.h \
                        osmocom/gsm/gsm29205.h \
                        osmocom/gsm/gsm0808_utils.h \
@@ -115,6 +116,7 @@ nobase_include_HEADERS = \
                        osmocom/gsm/l1sap.h \
                        osmocom/gsm/oap.h \
                        osmocom/gsm/oap_client.h \
+                       osmocom/gsm/protocol/gsm_23_032.h \
                        osmocom/gsm/protocol/gsm_03_40.h \
                        osmocom/gsm/protocol/gsm_03_41.h \
                        osmocom/gsm/protocol/gsm_04_08.h \
diff --git a/include/osmocom/gsm/gad.h b/include/osmocom/gsm/gad.h
new file mode 100644
index 000000000..57d0e37a9
--- /dev/null
+++ b/include/osmocom/gsm/gad.h
@@ -0,0 +1,190 @@
+/*! \addtogroup gad
+ *  @{
+ *  \file gad.h
+ *  Message encoding and decoding for 3GPP TS 23.032 GAD: Universal Geographical Area Description.
+ */
+/*
+ * (C) 2020 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#pragma once
+
+#include <osmocom/gsm/protocol/gsm_23_032.h>
+#include <osmocom/core/utils.h>
+
+struct msgb;
+
+struct osmo_gad_ell_point {
+	/*! Latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! Longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+};
+
+struct osmo_gad_ell_point_unc_circle {
+	/*! Latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! Longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! Uncertainty circle radius in millimeters (m * 1e3), 0 .. 18'000'000. */
+	uint32_t unc;
+};
+
+struct osmo_gad_ell_point_unc_ellipse {
+	/*! Latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! Longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! Uncertainty ellipsoid radius of major axis in millimeters, 0 .. 18'000'000.
+	 * Coding of uncertainty is non-linear, use osmo_gad_dec_unc(osmo_gad_enc_unc(val)) to clamp. */
+	uint32_t unc_semi_major;
+	/*! Uncertainty ellipsoid radius of minor axis in millimeters, 0 .. 18'000'000.
+	 * Coding of uncertainty is non-linear, use osmo_gad_dec_unc(osmo_gad_enc_unc(val)) to clamp. */
+	uint32_t unc_semi_minor;
+	/*! Major axis orientation in degrees (DEG), 0 (N) .. 90 (E) .. 179 (SSE). */
+	uint8_t major_ori;
+	/*! Confidence in percent, 0 = no information, 1..100%, 101..128 = no information. */
+	uint8_t confidence;
+};
+
+struct osmo_gad_polygon {
+	uint8_t num_points;
+	struct osmo_gad_ell_point point[15];
+};
+
+struct osmo_gad_ell_point_alt {
+	/*! latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! Altitude in meters, -32767 (depth) .. 32767 (height) */
+	int16_t alt;
+};
+
+struct osmo_gad_ell_point_alt_unc_ell {
+	/*! latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! Altitude in meters, -32767 (depth) .. 32767 (height) */
+	int16_t alt;
+	/*! Uncertainty ellipsoid radius of major axis in millimeters, 0 .. 18'000'000.
+	 * Coding of uncertainty is non-linear, use osmo_gad_dec_unc(osmo_gad_enc_unc(val)) to clamp. */
+	uint32_t unc_semi_major;
+	/*! Uncertainty ellipsoid radius of minor axis in millimeters, 0 .. 18'000'000.
+	 * Coding of uncertainty is non-linear, use osmo_gad_dec_unc(osmo_gad_enc_unc(val)) to clamp. */
+	uint32_t unc_semi_minor;
+	/*! Major axis orientation in degrees (DEG), 0 (N) .. 90 (E) .. 179 (SSE). */
+	uint8_t major_ori;
+	/*! Uncertainty altitude in millimeters, 0 .. 990'000.
+	 * Coding of uncertainty altitude is non-linear, and distinct from the non-altitude uncertainty coding. Use
+	 * osmo_gad_dec_unc_alt(osmo_gad_enc_unc_alt(val)) to clamp. */
+	int32_t unc_alt;
+	/*! Confidence in percent, 0 = no information, 1..100%, 101..128 = no information. */
+	uint8_t confidence;
+};
+
+struct osmo_gad_ell_arc {
+	/*! latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! inner circle radius in mm (m * 1e3) */
+	uint32_t inner_r;
+	/*! Uncertainty circle radius in millimeters, 0 .. 18'000'000.
+	 * Coding of uncertainty is non-linear, use osmo_gad_dec_unc(osmo_gad_enc_unc(val)) to clamp. */
+	uint32_t unc_r;
+	/*! Offset angle of first arc edge in degrees from North clockwise (eastwards), 0..359.
+	 * Angle is coded in increments of 2 degrees. */
+	uint16_t ofs_angle;
+	/*! Included angle defining the angular width of the arc, in degrees clockwise, 1..360.
+	 * Angle is coded in increments of 2 degrees. */
+	uint16_t incl_angle;
+	/*! Confidence in percent, 0 = no information, 1..100%, 101..128 = no information. */
+	uint8_t confidence;
+};
+
+struct osmo_gad_ha_ell_point_alt_unc_ell {
+	/*! latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N). */
+	int32_t lat;
+	/*! longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E). */
+	int32_t lon;
+	/*! Altitude in millimeters, -500'000 (depth) .. 10'000'000 (height) */
+	int32_t alt;
+	/*! Uncertainty ellipsoid radius of major axis in millimeters, 0 .. 46'491.
+	 * Coding of high-accuracy uncertainty is non-linear, use osmo_gad_dec_ha_unc(osmo_gad_enc_ha_unc(val)) to
+	 * clamp. */
+	uint32_t unc_semi_major;
+	/*! Uncertainty ellipsoid radius of minor axis in millimeters, 0 .. 46'491.
+	 * Coding of high-accuracy uncertainty is non-linear, use osmo_gad_dec_ha_unc(osmo_gad_enc_ha_unc(val)) to
+	 * clamp. */
+	uint32_t unc_semi_minor;
+	/*! Major axis orientation in degrees (DEG), 0 (N) .. 90 (E) .. 179 (SSE). */
+	uint8_t major_ori;
+	/*! Horizontal confidence in percent, 0 = no information, 1..100%, 101..128 = no information. */
+	uint8_t h_confidence;
+	/*! High-Accuracy uncertainty altitude */
+	int32_t unc_alt;
+	/*! Vertical confidence in percent, 0 = no information, 1..100%, 101..128 = no information. */
+	uint8_t v_confidence;
+};
+
+struct osmo_gad {
+	enum gad_type type;
+	union {
+		struct osmo_gad_ell_point ell_point;
+		struct osmo_gad_ell_point_unc_circle ell_point_unc_circle;
+		struct osmo_gad_ell_point_unc_ellipse ell_point_unc_ellipse;
+		struct osmo_gad_polygon polygon;
+		struct osmo_gad_ell_point_alt ell_point_alt;
+		struct osmo_gad_ell_point_alt_unc_ell ell_point_alt_unc_ell;
+		struct osmo_gad_ell_arc ell_arc;
+		struct osmo_gad_ell_point_unc_ellipse ha_ell_point_unc_ellipse;
+		struct osmo_gad_ha_ell_point_alt_unc_ell ha_ell_point_alt_unc_ell;
+	};
+};
+
+struct osmo_gad_err {
+	int rc;
+	enum gad_type type;
+	char *logmsg;
+};
+
+extern const struct value_string osmo_gad_type_names[];
+static inline const char *osmo_gad_type_name(enum gad_type val)
+{ return get_value_string(osmo_gad_type_names, val); }
+
+int osmo_gad_raw_write(struct msgb *msg, const union gad_raw *gad_raw);
+int osmo_gad_raw_read(union gad_raw *gad_raw, struct osmo_gad_err **err, void *err_ctx, const uint8_t *data, uint8_t len);
+
+int osmo_gad_enc(union gad_raw *gad_raw, const struct osmo_gad *gad);
+int osmo_gad_dec(struct osmo_gad *gad, struct osmo_gad_err **err, void *err_ctx, const union gad_raw *gad_raw);
+
+int osmo_gad_to_str_buf(char *buf, size_t buflen, const struct osmo_gad *gad);
+char *osmo_gad_to_str_c(void *ctx, const struct osmo_gad *gad);
+
+uint32_t osmo_gad_enc_lat(int32_t deg_1e6);
+int32_t osmo_gad_dec_lat(uint32_t lat);
+uint32_t osmo_gad_enc_lon(int32_t deg_1e6);
+int32_t osmo_gad_dec_lon(uint32_t lon);
+uint8_t osmo_gad_enc_unc(uint32_t mm);
+uint32_t osmo_gad_dec_unc(uint8_t unc);
+/*! @} */
diff --git a/include/osmocom/gsm/protocol/gsm_23_032.h b/include/osmocom/gsm/protocol/gsm_23_032.h
new file mode 100644
index 000000000..5be98a297
--- /dev/null
+++ b/include/osmocom/gsm/protocol/gsm_23_032.h
@@ -0,0 +1,172 @@
+/*! \defgroup gad 3GPP TS 23.032 GAD: Universal Geographical Area Description.
+ *  @{
+ *  \file gsm_23_032.h
+ */
+/*
+ * (C) 2020 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/endian.h>
+
+enum gad_type {
+	/*! Ellipsoid point */
+	GAD_TYPE_ELL_POINT = 0,
+	/*! Ellipsoid point with uncertainty circle. */
+	GAD_TYPE_ELL_POINT_UNC_CIRCLE = 1,
+	/*! Ellipsoid point with uncertainty ellipse. */
+	GAD_TYPE_ELL_POINT_UNC_ELLIPSE = 3,
+	GAD_TYPE_POLYGON = 5,
+	/*! Ellipsoid point with altitude. */
+	GAD_TYPE_ELL_POINT_ALT = 8,
+	/*! Ellipsoid point with altitude and uncertainty ellipsoid. */
+	GAD_TYPE_ELL_POINT_ALT_UNC_ELL = 9,
+	/*! Ellipsoid arc */
+	GAD_TYPE_ELL_ARC = 10,
+	/*! High accuracy ellipsoid point with uncertainty ellipse. */
+	GAD_TYPE_HA_ELL_POINT_UNC_ELLIPSE = 11,
+	/*! High accuracy ellipsoid point with altitude and uncertainty ellipsoid. */
+	GAD_TYPE_HA_ELL_POINT_ALT_UNC_ELL = 12,
+};
+
+struct gad_raw_head {
+	uint8_t spare:4,
+		type:4;
+} __attribute__ ((packed));
+
+struct gad_raw_ell_point {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_POINT */
+	uint8_t lat[3];
+	uint8_t lon[3];
+} __attribute__ ((packed));
+
+struct gad_raw_ell_point_unc_circle {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_POINT_UNC_CIRCLE */
+	uint8_t lat[3];
+	uint8_t lon[3];
+	uint8_t unc:7,
+		spare2:1;
+} __attribute__ ((packed));
+
+struct gad_raw_ell_point_unc_ellipse {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_POINT_UNC_ELLIPSE */
+	uint8_t lat[3];
+	uint8_t lon[3];
+	uint8_t unc_semi_major:7,
+		spare1:1;
+	uint8_t unc_semi_minor:7,
+		spare2:1;
+	uint8_t major_ori;
+	uint8_t confidence:7,
+		spare3:1;
+} __attribute__ ((packed));
+
+struct gad_raw_polygon {
+	struct {
+		uint8_t num_points:4;
+		uint8_t type:4; /*!< type = GAD_TYPE_POLYGON */
+	} h;
+	struct {
+		uint8_t lat[3];
+		uint8_t lon[3];
+	} point[15];
+} __attribute__ ((packed));
+
+struct gad_raw_ell_point_alt {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_POINT_ALT */
+	uint8_t lat[3];
+	uint8_t lon[3];
+	uint8_t alt[2];
+} __attribute__ ((packed));
+
+struct gad_raw_ell_point_alt_unc_ell {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_POINT_ALT_UNC_ELL */
+	uint8_t lat[3];
+	uint8_t lon[3];
+	uint8_t alt[2];
+	uint8_t unc_semi_major:7,
+		spare1:1;
+	uint8_t unc_semi_minor:7,
+		spare2:1;
+	uint8_t major_ori;
+	uint8_t unc_alt:7,
+		spare3:1;
+	uint8_t confidence:7,
+		spare4:1;
+} __attribute__ ((packed));
+
+struct gad_raw_ell_arc {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_ELL_ARC */
+	uint8_t lat[3];
+	uint8_t lon[3];
+	uint8_t inner_r[2];
+	uint8_t unc_r:7,
+		spare1:1;
+	uint8_t ofs_angle;
+	uint8_t incl_angle;
+	uint8_t confidence:7,
+		spare2:1;
+} __attribute__ ((packed));
+
+struct gad_raw_ha_ell_point_unc_ell {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_HA_ELL_POINT_UNC_ELLIPSE */
+	uint8_t lat[4];
+	uint8_t lon[4];
+	uint8_t alt[3];
+	uint8_t unc_semi_major;
+	uint8_t unc_semi_minor;
+	uint8_t major_ori;
+	uint8_t confidence:7,
+		spare1:1;
+} __attribute__ ((packed));
+
+struct gad_raw_ha_ell_point_alt_unc_ell {
+	struct gad_raw_head h; /*!< type = GAD_TYPE_HA_ELL_POINT_ALT_UNC_ELL */
+	uint8_t lat[4];
+	uint8_t lon[4];
+	uint8_t alt[3];
+	uint8_t unc_semi_major;
+	uint8_t unc_semi_minor;
+	uint8_t major_ori;
+	uint8_t h_confidence:7,
+		spare1:1;
+	uint8_t unc_alt;
+	uint8_t v_confidence:7,
+		spare2:1;
+} __attribute__ ((packed));
+
+/*! GAD PDU in network-byte-order according to 3GPP TS 23.032 GAD: Universal Geographical Area Description. */
+union gad_raw {
+	struct gad_raw_head h;
+	struct gad_raw_ell_point ell_point;
+	struct gad_raw_ell_point_unc_circle ell_point_unc_circle;
+	struct gad_raw_ell_point_unc_ellipse ell_point_unc_ellipse;
+	struct gad_raw_polygon polygon;
+	struct gad_raw_ell_point_alt ell_point_alt;
+	struct gad_raw_ell_point_alt_unc_ell ell_point_alt_unc_ell;
+	struct gad_raw_ell_arc ell_arc;
+	struct gad_raw_ha_ell_point_unc_ell ha_ell_point_unc_ell;
+	struct gad_raw_ha_ell_point_alt_unc_ell ha_ell_point_alt_unc_ell;
+} __attribute__ ((packed));
+
+/*! @} */
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index c5232abb8..4fa940be0 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -32,7 +32,8 @@ libgsmint_la_SOURCES =  a5.c rxlev_stat.c tlv_parser.c comp128.c comp128v23.c \
 			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
 			gsup.c gsup_sms.c gprs_gea.c gsm0503_conv.c oap.c gsm0808_utils.c \
 			gsm23003.c gsm23236.c mncc.c bts_features.c oap_client.c \
-			gsm29118.c gsm48_rest_octets.c cbsp.c gsm48049.c i460_mux.c
+			gsm29118.c gsm48_rest_octets.c cbsp.c gsm48049.c i460_mux.c \
+			gad.c
 libgsmint_la_LDFLAGS = -no-undefined
 libgsmint_la_LIBADD = $(top_builddir)/src/libosmocore.la
 
diff --git a/src/gsm/gad.c b/src/gsm/gad.c
new file mode 100644
index 000000000..3ec28f98c
--- /dev/null
+++ b/src/gsm/gad.c
@@ -0,0 +1,491 @@
+/* 3GPP TS 23.032 GAD: Universal Geographical Area Description */
+/*
+ * (C) 2020 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/gsm/gad.h>
+
+/*! \addtogroup gad
+ *  @{
+ *  \file gad.c
+ *  Message encoding and decoding for 3GPP TS 23.032 GAD: Universal Geographical Area Description.
+ */
+
+const struct value_string osmo_gad_type_names[] = {
+	{ GAD_TYPE_ELL_POINT, "Ellipsoid-point" },
+	{ GAD_TYPE_ELL_POINT_UNC_CIRCLE, "Ellipsoid-point-with-uncertainty-circle" },
+	{ GAD_TYPE_ELL_POINT_UNC_ELLIPSE, "Ellipsoid-point-with-uncertainty-ellipse" },
+	{ GAD_TYPE_POLYGON, "Polygon" },
+	{ GAD_TYPE_ELL_POINT_ALT, "Ellipsoid-point-with-altitude" },
+	{ GAD_TYPE_ELL_POINT_ALT_UNC_ELL, "Ellipsoid-point-with-altitude-and-uncertainty-ellipsoid" },
+	{ GAD_TYPE_ELL_ARC, "Ellipsoid-arc" },
+	{ GAD_TYPE_HA_ELL_POINT_UNC_ELLIPSE, "High-accuracy-ellipsoid-point-with-uncertainty-ellipse" },
+	{ GAD_TYPE_HA_ELL_POINT_ALT_UNC_ELL, "High-accuracy-ellipsoid-point-with-altitude-and-uncertainty-ellipsoid" },
+	{}
+};
+
+/*! Encode a latitude value according to 3GPP TS 23.032.
+ * Useful to clamp a latitude to an actually encodable accuracy:
+ * set_lat = osmo_gad_dec_lat(osmo_gad_enc_lat(orig_lat));
+ * \param[in] deg_1e6  Latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N).
+ * \returns encoded latitude in host-byte-order (24bit).
+ */
+uint32_t osmo_gad_enc_lat(int32_t deg_1e6)
+{
+	/* N <= ((2**23)/90)*X < N+1
+	 * N: encoded latitude
+	 * X: latitude in degrees
+	 */
+	int32_t sign = 0;
+	int64_t x;
+	deg_1e6 = OSMO_MAX(-90000000, OSMO_MIN(90000000, deg_1e6));
+	if (deg_1e6 < 0) {
+		sign = 1 << 23;
+		deg_1e6 = -deg_1e6;
+	}
+	x = deg_1e6;
+	x <<= 23;
+	x += (1 << 23) - 1;
+	x /= 90 * 1000000;
+	return sign | (x & 0x7fffff);
+}
+
+/*! Decode a latitude value according to 3GPP TS 23.032.
+ * Useful to clamp a latitude to an actually encodable accuracy:
+ * set_lat = osmo_gad_dec_lat(osmo_gad_enc_lat(orig_lat));
+ * \param[in] lat  encoded latitude in host-byte-order (24bit).
+ * \returns decoded latitude in micro degrees (degrees * 1e6), -90'000'000 (S) .. 90'000'000 (N).
+ */
+int32_t osmo_gad_dec_lat(uint32_t lat)
+{
+	int64_t sign = 1;
+	int64_t x;
+	if (lat & 0x800000) {
+		sign = -1;
+		lat &= 0x7fffff;
+	}
+	x = lat;
+	x *= 90 * 1000000;
+	x >>= 23;
+	x *= sign;
+	return x;
+}
+
+/*! Encode a longitude value according to 3GPP TS 23.032.
+ * Useful to clamp a longitude to an actually encodable accuracy:
+ * set_lon = osmo_gad_dec_lon(osmo_gad_enc_lon(orig_lon));
+ * \param[in] deg_1e6  Longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E).
+ * \returns encoded longitude in host-byte-order (24bit).
+ */
+uint32_t osmo_gad_enc_lon(int32_t deg_1e6)
+{
+	/* -180 .. 180 degrees mapped to a signed 24 bit integer.
+	 * N <= ((2**24)/360) * X < N+1
+	 * N: encoded longitude
+	 * X: longitude in degrees
+	 */
+	int64_t x;
+	deg_1e6 = OSMO_MAX(-180000000, OSMO_MIN(180000000, deg_1e6));
+	x = deg_1e6;
+	x *= (1 << 24);
+	if (deg_1e6 >= 0)
+		x += (1 << 24) - 1;
+	else
+		x -= (1 << 24) - 1;
+	x /= 360 * 1000000;
+	return (uint32_t)(x & 0xffffff);
+}
+
+/*! Decode a longitude value according to 3GPP TS 23.032.
+ * Normally, encoding and decoding is done via osmo_gad_enc() and osmo_gad_dec() for entire PDUs. But calling this
+ * directly can be useful to clamp a longitude to an actually encodable accuracy:
+ * int32_t set_lon = osmo_gad_dec_lon(osmo_gad_enc_lon(orig_lon));
+ * \param[in] lon  Encoded longitude.
+ * \returns Longitude in micro degrees (degrees * 1e6), -180'000'000 (W) .. 180'000'000 (E).
+ */
+int32_t osmo_gad_dec_lon(uint32_t lon)
+{
+	/* -180 .. 180 degrees mapped to a signed 24 bit integer.
+	 * N <= ((2**24)/360) * X < N+1
+	 * N: encoded longitude
+	 * X: longitude in degrees
+	 */
+	int32_t slon;
+	int64_t x;
+	if (lon & 0x800000) {
+		/* make the 24bit negative number to a 32bit negative number */
+		slon = lon | 0xff000000;
+	} else {
+		slon = lon;
+	}
+	x = slon;
+	x *= 360 * 1000000;
+	x /= (1 << 24);
+	return x;
+}
+
+/*
+ * r = C((1+x)**K - 1)
+ * C = 10, x = 0.1
+ *
+ * def r(k):
+ *     return 10.*(((1+0.1)**k) -1 )
+ * for k in range(128):
+ *     print('%d,' % (r(k) * 1000.))
+ */
+static uint32_t table_uncertainty_1e3[128] = {
+	0, 1000, 2100, 3310, 4641, 6105, 7715, 9487, 11435, 13579, 15937, 18531, 21384, 24522, 27974, 31772, 35949,
+	40544, 45599, 51159, 57274, 64002, 71402, 79543, 88497, 98347, 109181, 121099, 134209, 148630, 164494, 181943,
+	201137, 222251, 245476, 271024, 299126, 330039, 364043, 401447, 442592, 487851, 537636, 592400, 652640, 718904,
+	791795, 871974, 960172, 1057189, 1163908, 1281299, 1410429, 1552472, 1708719, 1880591, 2069650, 2277615,
+	2506377, 2758014, 3034816, 3339298, 3674227, 4042650, 4447915, 4893707, 5384077, 5923485, 6516834, 7169517,
+	7887469, 8677216, 9545938, 10501531, 11552685, 12708953, 13980849, 15379933, 16918927, 18611820, 20474002,
+	22522402, 24775642, 27254206, 29980627, 32979690, 36278659, 39907525, 43899277, 48290205, 53120226, 58433248,
+	64277573, 70706330, 77777964, 85556760, 94113436, 103525780, 113879358, 125268293, 137796123, 151576735,
+	166735409, 183409950, 201751945, 221928139, 244121953, 268535149, 295389664, 324929630, 357423593, 393166952,
+	432484648, 475734112, 523308524, 575640376, 633205414, 696526955, 766180651, 842799716, 927080688, 1019789756,
+	1121769732, 1233947705, 1357343476, 1493078824, 1642387706, 1806627477,
+};
+
+/*! Decode an uncertainty circle value according to 3GPP TS 23.032.
+ * Useful to clamp a value to an actually encodable accuracy:
+ * set_unc = osmo_gad_dec_unc(osmo_gad_enc_unc(orig_unc));
+ * \param[in] unc  Encoded uncertainty value.
+ * \returns Uncertainty value in millimeters.
+ */
+uint32_t osmo_gad_dec_unc(uint8_t unc)
+{
+	return table_uncertainty_1e3[unc & 0x7f];
+}
+
+/*! Encode an uncertainty circle value according to 3GPP TS 23.032.
+ * Normally, encoding and decoding is done via osmo_gad_enc() and osmo_gad_dec() for entire PDUs. But calling this
+ * directly can be useful to clamp a value to an actually encodable accuracy:
+ * uint32_t set_unc = osmo_gad_dec_unc(osmo_gad_enc_unc(orig_unc));
+ * \param[in] mm  Uncertainty value in millimeters.
+ * \returns  Encoded uncertainty value.
+ */
+uint8_t osmo_gad_enc_unc(uint32_t mm)
+{
+	uint8_t unc;
+	for (unc = 0; unc < ARRAY_SIZE(table_uncertainty_1e3); unc++) {
+		if (table_uncertainty_1e3[unc] > mm)
+			return unc - 1;
+	}
+	return 127;
+}
+
+/* So far we don't encode a high-accuracy uncertainty anywhere, so these static items would flag as compiler warnings
+ * for unused items. As soon as any HA items get used, remove this ifdef. */
+#ifdef GAD_FUTURE
+
+/*
+ * r = C((1+x)**K - 1)
+ * C = 0.3, x = 0.02
+ *
+ * def r(k):
+ *     return 0.3*(((1+0.02)**k) -1 )
+ * for k in range(256):
+ *     print('%d,' % (r(k) * 1000.))
+ */
+static uint32_t table_ha_uncertainty_1e3[256] = {
+	0, 6, 12, 18, 24, 31, 37, 44, 51, 58, 65, 73, 80, 88, 95, 103, 111, 120, 128, 137, 145, 154, 163, 173, 182, 192,
+	202, 212, 222, 232, 243, 254, 265, 276, 288, 299, 311, 324, 336, 349, 362, 375, 389, 402, 417, 431, 445, 460,
+	476, 491, 507, 523, 540, 556, 574, 591, 609, 627, 646, 665, 684, 703, 724, 744, 765, 786, 808, 830, 853, 876,
+	899, 923, 948, 973, 998, 1024, 1051, 1078, 1105, 1133, 1162, 1191, 1221, 1252, 1283, 1314, 1347, 1380, 1413,
+	1447, 1482, 1518, 1554, 1592, 1629, 1668, 1707, 1748, 1788, 1830, 1873, 1916, 1961, 2006, 2052, 2099, 2147,
+	2196, 2246, 2297, 2349, 2402, 2456, 2511, 2567, 2625, 2683, 2743, 2804, 2866, 2929, 2994, 3060, 3127, 3195,
+	3265, 3336, 3409, 3483, 3559, 3636, 3715, 3795, 3877, 3961, 4046, 4133, 4222, 4312, 4404, 4498, 4594, 4692,
+	4792, 4894, 4998, 5104, 5212, 5322, 5435, 5549, 5666, 5786, 5907, 6032, 6158, 6287, 6419, 6554, 6691, 6830,
+	6973, 7119, 7267, 7418, 7573, 7730, 7891, 8055, 8222, 8392, 8566, 8743, 8924, 9109, 9297, 9489, 9685, 9884,
+	10088, 10296, 10508, 10724, 10944, 11169, 11399, 11633, 11871, 12115, 12363, 12616, 12875, 13138, 13407, 13681,
+	13961, 14246, 14537, 14834, 15136, 15445, 15760, 16081, 16409, 16743, 17084, 17431, 17786, 18148, 18517, 18893,
+	19277, 19669, 20068, 20475, 20891, 21315, 21747, 22188, 22638, 23096, 23564, 24042, 24529, 25025, 25532, 26048,
+	26575, 27113, 27661, 28220, 28791, 29372, 29966, 30571, 31189, 31818, 32461, 33116, 33784, 34466, 35161, 35871,
+	36594, 37332, 38085, 38852, 39635, 40434, 41249, 42080, 42927, 43792, 44674, 45573, 46491,
+};
+
+static uint32_t osmo_gad_dec_ha_unc(uint8_t unc)
+{
+	return table_uncertainty_1e3[unc];
+}
+
+static uint8_t osmo_gad_enc_ha_unc(uint32_t mm)
+{
+	uint8_t unc;
+	for (unc = 0; unc < ARRAY_SIZE(table_ha_uncertainty_1e3); unc++) {
+		if (table_uncertainty_1e3[unc] > mm)
+			return unc - 1;
+	}
+	return 255;
+}
+
+#endif /* GAD_FUTURE */
+
+/* Return error code, and, if required, allocate and populate struct osmo_gad_err. */
+#define DEC_ERR(RC, TYPE, fmt, args...) do { \
+		if (err) { \
+			*err = talloc_zero(err_ctx, struct osmo_gad_err); \
+			**err = (struct osmo_gad_err){ \
+				.rc = (RC), \
+				.type = (TYPE), \
+				.logmsg = talloc_asprintf(*err, "Error decoding GAD%s%s: " fmt, \
+							  (TYPE) >= 0 ? " " : "", \
+							  (TYPE) >= 0 ? osmo_gad_type_name(TYPE) : "", ##args), \
+			}; \
+		} \
+		return RC; \
+	} while(0)
+
+static int osmo_gad_enc_ell_point_unc_circle(struct gad_raw_ell_point_unc_circle *raw, const struct osmo_gad_ell_point_unc_circle *v)
+{
+	if (v->lat < -90000000 || v->lat > 90000000)
+		return -EINVAL;
+	if (v->lon < -180000000 || v->lon > 180000000)
+		return -EINVAL;
+	*raw = (struct gad_raw_ell_point_unc_circle){
+		.h = { .type = GAD_TYPE_ELL_POINT_UNC_CIRCLE },
+		.unc = osmo_gad_enc_unc(v->unc),
+	};
+	osmo_store32be_ext(osmo_gad_enc_lat(v->lat), raw->lat, 3);
+	osmo_store32be_ext(osmo_gad_enc_lon(v->lon), raw->lon, 3);
+	return sizeof(&raw);
+}
+
+static int osmo_gad_dec_ell_point_unc_circle(struct osmo_gad_ell_point_unc_circle *v,
+					     struct osmo_gad_err **err, void *err_ctx,
+					     const struct gad_raw_ell_point_unc_circle *raw)
+{
+	/* Load 24bit big endian */
+	v->lat = osmo_gad_dec_lat(osmo_load32be_ext_2(raw->lat, 3));
+	v->lon = osmo_gad_dec_lon(osmo_load32be_ext_2(raw->lon, 3));
+
+	if (raw->spare2)
+		DEC_ERR(-EINVAL, raw->h.type, "Bit 8 of Uncertainty code should be zero");
+
+	v->unc = osmo_gad_dec_unc(raw->unc);
+	return 0;
+}
+
+static int osmo_gad_raw_len(const union gad_raw *gad_raw)
+{
+	switch (gad_raw->h.type) {
+	case GAD_TYPE_ELL_POINT:
+		return sizeof(gad_raw->ell_point);
+	case GAD_TYPE_ELL_POINT_UNC_CIRCLE:
+		return sizeof(gad_raw->ell_point_unc_circle);
+	case GAD_TYPE_ELL_POINT_UNC_ELLIPSE:
+		return sizeof(gad_raw->ell_point_unc_ellipse);
+	case GAD_TYPE_POLYGON:
+		if (gad_raw->polygon.h.num_points < 3)
+			return -EINVAL;
+		return sizeof(gad_raw->polygon.h)
+			+ gad_raw->polygon.h.num_points * sizeof(gad_raw->polygon.point[0]);
+	case GAD_TYPE_ELL_POINT_ALT:
+		return sizeof(gad_raw->ell_point_alt);
+	case GAD_TYPE_ELL_POINT_ALT_UNC_ELL:
+		return sizeof(gad_raw->ell_point_alt_unc_ell);
+	case GAD_TYPE_ELL_ARC:
+		return sizeof(gad_raw->ell_arc);
+	case GAD_TYPE_HA_ELL_POINT_UNC_ELLIPSE:
+		return sizeof(gad_raw->ha_ell_point_unc_ell);
+	case GAD_TYPE_HA_ELL_POINT_ALT_UNC_ELL:
+		return sizeof(gad_raw->ha_ell_point_alt_unc_ell);
+	default:
+		return -ENOTSUP;
+	}
+}
+
+/*! Append a GAD PDU to the msgb.
+ * Write the correct number of bytes depending on the GAD type and possibly on variable length attributes.
+ * \param[out] msg  Append to this msgb.
+ * \param[in] gad_raw  GAD data to write.
+ * \returns number of bytes appended to msgb, or negative on failure.
+ */
+int osmo_gad_raw_write(struct msgb *msg, const union gad_raw *gad_raw)
+{
+	int len;
+	uint8_t *dst;
+	len = osmo_gad_raw_len(gad_raw);
+	if (len < 0)
+		return len;
+	dst = msgb_put(msg, len);
+	memcpy(dst, (void*)gad_raw, len);
+	return len;
+}
+
+/*! Read a GAD PDU and validate structure.
+ * Memcpy from data to gad_raw struct, and validate correct length depending on the GAD type and possibly on variable
+ * length attributes.
+ * \param[out] gad_raw  Copy GAD PDU here.
+ * \param[out] err  Returned pointer to error info, dynamically allocated; NULL to not return any.
+ * \param[in] err_ctx  Talloc context to allocate err from, if required.
+ * \param[in] data  Encoded GAD bytes buffer.
+ * \param[in] len  Length of data in bytes.
+ * \returns 0 on success, negative on error. If returning negative and err was non-NULL, *err is guaranteed to point to
+ *          an allocated struct osmo_gad_err.
+ */
+int osmo_gad_raw_read(union gad_raw *gad_raw, struct osmo_gad_err **err, void *err_ctx, const uint8_t *data, uint8_t len)
+{
+	int gad_len;
+	const union gad_raw *src;
+	if (err)
+		*err = NULL;
+	if (len < sizeof(src->h))
+		DEC_ERR(-EINVAL, -1, "GAD data too short for header (%u bytes)", len);
+
+	src = (void*)data;
+	gad_len = osmo_gad_raw_len(src);
+	if (gad_len < 0)
+		DEC_ERR(-EINVAL, src->h.type, "GAD data invalid (rc=%d)", gad_len);
+	if (gad_len != len)
+		DEC_ERR(-EINVAL, src->h.type, "GAD data with unexpected length: expected %d bytes, got %u",
+			gad_len, len);
+
+	memcpy((void*)gad_raw, data, gad_len);
+	return 0;
+}
+
+/*! Write GAD values with consistent units to raw GAD PDU representation.
+ * \param[out] gad_raw  Write to this buffer.
+ * \param[in] gad  GAD values to encode.
+ * \returns number of bytes written, or negative on failure.
+ */
+int osmo_gad_enc(union gad_raw *gad_raw, const struct osmo_gad *gad)
+{
+	switch (gad->type) {
+	case GAD_TYPE_ELL_POINT_UNC_CIRCLE:
+		return osmo_gad_enc_ell_point_unc_circle(&gad_raw->ell_point_unc_circle, &gad->ell_point_unc_circle);
+	default:
+		return -ENOTSUP;
+	}
+}
+
+/*! Decode GAD raw PDU to values with consistent units.
+ * \param[out] gad  Decoded GAD values are written here.
+ * \param[out] err  Returned pointer to error info, dynamically allocated; NULL to not return any.
+ * \param[in] err_ctx  Talloc context to allocate err from, if required.
+ * \param[in] raw  Raw GAD data in network-byte-order.
+ * \returns 0 on success, negative on error. If returning negative and err was non-NULL, *err is guaranteed to point to
+ *          an allocated struct osmo_gad_err.
+ */
+int osmo_gad_dec(struct osmo_gad *gad, struct osmo_gad_err **err, void *err_ctx, const union gad_raw *raw)
+{
+	*gad = (struct osmo_gad){
+		.type = raw->h.type,
+	};
+	switch (raw->h.type) {
+	case GAD_TYPE_ELL_POINT_UNC_CIRCLE:
+		return osmo_gad_dec_ell_point_unc_circle(&gad->ell_point_unc_circle, err, err_ctx,
+							 &raw->ell_point_unc_circle);
+	default:
+		DEC_ERR(-ENOTSUP, raw->h.type, "unsupported GAD type");
+	}
+}
+
+/*! Return a human readable representation of a raw GAD PDU.
+ * Convert to GAD values and feed the result to osmo_gad_to_str_buf().
+ * \param[out] buf  Buffer to write string to.
+ * \param[in] buflen  sizeof(buf).
+ * \param[in] gad  Location data.
+ * \returns number of chars that would be written, like snprintf().
+ */
+int osmo_gad_raw_to_str_buf(char *buf, size_t buflen, const union gad_raw *raw)
+{
+	struct osmo_gad gad;
+	if (osmo_gad_dec(&gad, NULL, NULL, raw)) {
+		struct osmo_strbuf sb = { .buf = buf, .len = buflen };
+		OSMO_STRBUF_PRINTF(sb, "invalid");
+		return sb.chars_needed;
+	}
+	return osmo_gad_to_str_buf(buf, buflen, &gad);
+}
+
+/*! Return a human readable representation of a raw GAD PDU.
+ * Convert to GAD values and feed the result to osmo_gad_to_str_buf().
+ * \param[in] ctx  Talloc ctx to allocate string buffer from.
+ * \param[in] raw  GAD data in network-byte-order.
+ * \returns resulting string, dynamically allocated.
+ */
+char *osmo_gad_raw_to_str_c(void *ctx, const union gad_raw *raw)
+{
+	OSMO_NAME_C_IMPL(ctx, 128, "ERROR", osmo_gad_raw_to_str_buf, raw)
+}
+
+/*! Return a human readable representation of GAD (location estimate) values.
+ * \param[out] buf  Buffer to write string to.
+ * \param[in] buflen  sizeof(buf).
+ * \param[in] gad  Location data.
+ * \returns number of chars that would be written, like snprintf().
+ */
+int osmo_gad_to_str_buf(char *buf, size_t buflen, const struct osmo_gad *gad)
+{
+	struct osmo_strbuf sb = { .buf = buf, .len = buflen };
+
+	if (!gad) {
+		OSMO_STRBUF_PRINTF(sb, "null");
+		return sb.chars_needed;
+	}
+
+	OSMO_STRBUF_PRINTF(sb, "%s{", osmo_gad_type_name(gad->type));
+
+	switch (gad->type) {
+	case GAD_TYPE_ELL_POINT:
+		OSMO_STRBUF_PRINTF(sb, "lat=");
+		OSMO_STRBUF_APPEND(sb, osmo_int_to_float_str_buf, gad->ell_point.lat, 6);
+		OSMO_STRBUF_PRINTF(sb, ",lon=");
+		OSMO_STRBUF_APPEND(sb, osmo_int_to_float_str_buf, gad->ell_point.lon, 6);
+		break;
+
+	case GAD_TYPE_ELL_POINT_UNC_CIRCLE:
+		OSMO_STRBUF_PRINTF(sb, "lat=");
+		OSMO_STRBUF_APPEND(sb, osmo_int_to_float_str_buf, gad->ell_point_unc_circle.lat, 6);
+		OSMO_STRBUF_PRINTF(sb, ",lon=");
+		OSMO_STRBUF_APPEND(sb, osmo_int_to_float_str_buf, gad->ell_point_unc_circle.lon, 6);
+		OSMO_STRBUF_PRINTF(sb, ",unc=");
+		OSMO_STRBUF_APPEND(sb, osmo_int_to_float_str_buf, gad->ell_point_unc_circle.unc, 3);
+		OSMO_STRBUF_PRINTF(sb, "m");
+		break;
+
+	default:
+		OSMO_STRBUF_PRINTF(sb, "to-str-not-implemented");
+		break;
+	}
+
+	OSMO_STRBUF_PRINTF(sb, "}");
+	return sb.chars_needed;
+}
+
+/*! Return a human readable representation of GAD (location estimate) values.
+ * \param[in] ctx  Talloc ctx to allocate string buffer from.
+ * \param[in] val  Value to convert to float.
+ * \returns resulting string, dynamically allocated.
+ */
+char *osmo_gad_to_str_c(void *ctx, const struct osmo_gad *gad)
+{
+	OSMO_NAME_C_IMPL(ctx, 128, "ERROR", osmo_gad_to_str_buf, gad)
+}
+
+/*! @} */
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 4ece10790..a31f73aa3 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -705,5 +705,16 @@ osmo_nri_ranges_vty_del;
 osmo_nri_ranges_to_str_buf;
 osmo_nri_ranges_to_str_c;
 
+osmo_gad_enc;
+osmo_gad_dec;
+osmo_gad_to_str_buf;
+osmo_gad_to_str_c;
+osmo_gad_enc_lat;
+osmo_gad_dec_lat;
+osmo_gad_enc_lon;
+osmo_gad_dec_lon;
+osmo_gad_enc_unc;
+osmo_gad_dec_unc;
+
 local: *;
 };
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2d0cf939f..c4e6b9f5a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -38,6 +38,7 @@ check_PROGRAMS = timer/timer_test sms/sms_test ussd/ussd_test		\
                  dtx/dtx_gsm0503_test					\
                  i460_mux/i460_mux_test					\
 		 bitgen/bitgen_test					\
+		 gad/gad_test						\
 		 $(NULL)
 
 if ENABLE_MSGFILE
@@ -281,6 +282,9 @@ i460_mux_i460_mux_test_LDADD = $(LDADD) $(top_builddir)/src/gsm/libosmogsm.la
 bitgen_bitgen_test_SOURCES = bitgen/bitgen_test.c
 bitgen_bitgen_test_LDADD = $(LDADD)
 
+gad_gad_test_SOURCES = gad/gad_test.c
+gad_gad_test_LDADD = $(LDADD) $(top_builddir)/src/gsm/gad.o
+
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
 	:;{ \
@@ -361,6 +365,7 @@ EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE)		\
 	     exec/exec_test.ok exec/exec_test.err \
 	     i460_mux/i460_mux_test.ok \
 	     bitgen/bitgen_test.ok \
+	     gad/gad_test.ok \
 	     $(NULL)
 
 if ENABLE_LIBSCTP
diff --git a/tests/gad/gad_test.c b/tests/gad/gad_test.c
new file mode 100644
index 000000000..ca8c4fa88
--- /dev/null
+++ b/tests/gad/gad_test.c
@@ -0,0 +1,143 @@
+#include <stdio.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/gsm/gad.h>
+
+void test_gad_lat_lon_dec_enc_stability()
+{
+	uint32_t lat_enc;
+	uint32_t lon_enc;
+	printf("--- %s\n", __func__);
+	for (lat_enc = 0x0; lat_enc <= 0xffffff; lat_enc++) {
+		int32_t lat_dec = osmo_gad_dec_lat(lat_enc);
+		uint32_t enc2 = osmo_gad_enc_lat(lat_dec);
+		uint32_t want_enc = lat_enc;
+		/* "-0" == 0, because the highest bit is defined as a sign bit. */
+		if (lat_enc == 0x800000)
+			want_enc = 0;
+		if (enc2 != want_enc) {
+			printf("ERR: lat=%u --> %d --> %u\n", lat_enc, lat_dec, enc2);
+			printf("%d -> %u\n", lat_dec + 1, osmo_gad_enc_lat(lat_dec + 1));
+			OSMO_ASSERT(false);
+		}
+	}
+	printf("osmo_gad_dec_lat() -> osmo_gad_enc_lat() of %u values successful\n", lat_enc);
+	for (lon_enc = 0; lon_enc <= 0xffffff; lon_enc++) {
+		int32_t lon_dec = osmo_gad_dec_lon(lon_enc);
+		uint32_t enc2 = osmo_gad_enc_lon(lon_dec);
+		uint32_t want_enc = lon_enc;
+		if (enc2 != want_enc) {
+			printf("ERR: lon=%u 0x%x --> %d --> %u\n", lon_enc, lon_enc, lon_dec, enc2);
+			printf("%d -> %u\n", lon_dec + 1, osmo_gad_enc_lon(lon_dec + 1));
+			printf("%d -> %u\n", lon_dec - 1, osmo_gad_enc_lon(lon_dec - 1));
+			OSMO_ASSERT(false);
+		}
+	}
+	printf("osmo_gad_dec_lon() -> osmo_gad_enc_lon() of %u values successful\n", lon_enc);
+}
+
+struct osmo_gad gad_test_values[] = {
+	{
+		.type = GAD_TYPE_ELL_POINT_UNC_CIRCLE,
+		.ell_point_unc_circle = {
+			/* Values rounded to the nearest encodable value, for test result matching */
+			.lat = 23000006,
+			.lon = 42000002,
+			.unc = 442592,
+		},
+	},
+};
+
+void test_gad_enc_dec()
+{
+	int i;
+	printf("--- %s\n", __func__);
+
+	for (i = 0; i < ARRAY_SIZE(gad_test_values); i++) {
+		struct osmo_gad *t = &gad_test_values[i];
+		struct msgb *msg = msgb_alloc(1024, __func__);
+		union gad_raw raw_write;
+		union gad_raw raw_read;
+		struct osmo_gad dec_pdu;
+		int rc;
+		struct osmo_gad_err *err;
+		void *loop_ctx = msg;
+		rc = osmo_gad_enc(&raw_write, t);
+		if (rc <= 0) {
+			printf("[%d] %s: ERROR: osmo_gad_enc() failed\n", i, osmo_gad_type_name(t->type));
+			goto loop_end;
+		}
+		rc = osmo_gad_raw_write(msg, &raw_write);
+		if (rc <= 0) {
+			printf("[%d] %s: ERROR: osmo_gad_raw_write() failed\n", i, osmo_gad_type_name(t->type));
+			goto loop_end;
+		}
+		if (rc != msg->len) {
+			printf("[%d] %s: ERROR: osmo_gad_raw_write() returned length %d but msgb has %d bytes\n",
+			       i, osmo_gad_type_name(t->type),
+			       rc, msg->len);
+			goto loop_end;
+		}
+
+		memset(&raw_read, 0xff, sizeof(raw_read));
+		rc = osmo_gad_raw_read(&raw_read, &err, loop_ctx, msg->data, msg->len);
+		if (rc) {
+			printf("[%d] ERROR: osmo_gad_raw_read() failed: %s\n", i, err->logmsg);
+			printf("    encoded data: %s\n", osmo_hexdump(msg->data, msg->len));
+			goto loop_end;
+		}
+
+		memset(&dec_pdu, 0xff, sizeof(dec_pdu));
+		rc = osmo_gad_dec(&dec_pdu, &err, loop_ctx, &raw_read);
+		if (rc) {
+			printf("[%d] ERROR: failed to decode pdu: %s\n", i, err->logmsg);
+			printf("    encoded data: %s\n", osmo_hexdump(msg->data, msg->len));
+			goto loop_end;
+		}
+
+		if (memcmp(t, &dec_pdu, sizeof(dec_pdu))) {
+			char strbuf[128];
+			printf("[%d] %s: ERROR: decoded PDU != encoded PDU\n", i,
+			       osmo_gad_type_name(t->type));
+			osmo_gad_to_str_buf(strbuf, sizeof(strbuf), t);
+			printf("     original struct: %s\n", strbuf);
+			osmo_gad_to_str_buf(strbuf, sizeof(strbuf), &dec_pdu);
+			printf("      decoded struct: %s\n", strbuf);
+			goto loop_end;
+		}
+
+		printf("[%d] %s: ok\n", i, osmo_gad_type_name(t->type));
+		printf("    encoded data: %s\n", msgb_hexdump(msg));
+
+loop_end:
+		msgb_free(msg);
+	}
+}
+
+void test_gad_to_str()
+{
+	int i;
+	printf("--- %s\n", __func__);
+
+	for (i = 0; i < ARRAY_SIZE(gad_test_values); i++) {
+		struct osmo_gad *t = &gad_test_values[i];
+		char buf[1024];
+		int rc;
+		rc = osmo_gad_to_str_buf(buf, sizeof(buf), t);
+
+		printf("[%d] ", i);
+		if (rc <= 0)
+			printf("%s: ERROR: osmo_gad_to_str_buf() failed\n", osmo_gad_type_name(t->type));
+		else
+			printf("%s\n", buf);
+	}
+}
+
+int main()
+{
+	test_gad_lat_lon_dec_enc_stability();
+	test_gad_enc_dec();
+	test_gad_to_str();
+	return 0;
+}
diff --git a/tests/gad/gad_test.ok b/tests/gad/gad_test.ok
new file mode 100644
index 000000000..ec5432a86
--- /dev/null
+++ b/tests/gad/gad_test.ok
@@ -0,0 +1,8 @@
+--- test_gad_lat_lon_dec_enc_stability
+osmo_gad_dec_lat() -> osmo_gad_enc_lat() of 16777216 values successful
+osmo_gad_dec_lon() -> osmo_gad_enc_lon() of 16777216 values successful
+--- test_gad_enc_dec
+[0] Ellipsoid-point-with-uncertainty-circle: ok
+    encoded data: 10 20 b6 0c 1d dd de 28 
+--- test_gad_to_str
+[0] Ellipsoid-point-with-uncertainty-circle{lat=23.000006,lon=42.000002,unc=442.592m}
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 8b6a20a18..e29c13127 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -403,3 +403,9 @@ AT_KEYWORDS([bitgen])
 cat $abs_srcdir/bitgen/bitgen_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/bitgen/bitgen_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([gad])
+AT_KEYWORDS([gad])
+cat $abs_srcdir/gad/gad_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/gad/gad_test], [0], [expout], [ignore])
+AT_CLEANUP