diff --git a/src/main/blackbox/blackbox.c b/src/main/blackbox/blackbox.c
index 0ef8467cdf..25296e9730 100644
--- a/src/main/blackbox/blackbox.c
+++ b/src/main/blackbox/blackbox.c
@@ -277,7 +277,7 @@ static const blackboxConditionalFieldDefinition_t blackboxGpsGFields[] = {
     {"GPS_numSat",        -1, UNSIGNED, PREDICT(0),          ENCODING(UNSIGNED_VB), CONDITION(ALWAYS)},
     {"GPS_coord",          0, SIGNED,   PREDICT(HOME_COORD), ENCODING(SIGNED_VB),   CONDITION(ALWAYS)},
     {"GPS_coord",          1, SIGNED,   PREDICT(HOME_COORD), ENCODING(SIGNED_VB),   CONDITION(ALWAYS)},
-    {"GPS_altitude",      -1, UNSIGNED, PREDICT(0),          ENCODING(UNSIGNED_VB), CONDITION(ALWAYS)},
+    {"GPS_altitude",      -1, SIGNED,   PREDICT(0),          ENCODING(SIGNED_VB),   CONDITION(ALWAYS)},
     {"GPS_speed",         -1, UNSIGNED, PREDICT(0),          ENCODING(UNSIGNED_VB), CONDITION(ALWAYS)},
     {"GPS_ground_course", -1, UNSIGNED, PREDICT(0),          ENCODING(UNSIGNED_VB), CONDITION(ALWAYS)}
 };
@@ -1110,7 +1110,7 @@ static void writeGPSFrame(timeUs_t currentTimeUs)
     blackboxWriteUnsignedVB(gpsSol.numSat);
     blackboxWriteSignedVB(gpsSol.llh.lat - gpsHistory.GPS_home[GPS_LATITUDE]);
     blackboxWriteSignedVB(gpsSol.llh.lon - gpsHistory.GPS_home[GPS_LONGITUDE]);
-    blackboxWriteUnsignedVB(gpsSol.llh.altCm / 10); // was originally designed to transport meters in int16, but +-3276.7m is a good compromise
+    blackboxWriteSignedVB(gpsSol.llh.altCm / 10);  // log altitude in increments of 0.1m
     blackboxWriteUnsignedVB(gpsSol.groundSpeed);
     blackboxWriteUnsignedVB(gpsSol.groundCourse);