Z information from reach compare to other GNSS: 50 m of difference!

[Seb_B (Bauwens Sebastien)]

Hello,

We have used 3 different GNSS in our drone (ublox, ellipse & reach). The Z information from ublox and ellipse are very similar (Z= 152,66 m) in contrast to the reach one (Z=200,2 m) (more information below as attached file .txt are not allowed)!

I suppose it is a difference in the reference datum, but could we have more information on this?

Regards,

Sébastien

Ellipse (au sol) :
Time Stamp GPS Date GPS Time UTC Date UTC Time Roll Pitch Yaw Latitude Longitude Pitch Yaw Altitude MSL Status Num Sv Used Latitude Longitude Altitude MSL
(s) (YYYY-MM-DD) (HH:MM:SS.SS (YYYY-MM-DD) (HH:MM:SS.SS (°) (°) (°) (°) (°) (°) (°) (m) (-) (int) (°) (°) (m)
34.042 2018-05-25.032 15:11:45.032 2018-05-25.032 15:11:27.032 0.909 1.914 159.240 50.5639149000 4.6998738000 153.427 DIFF 15 50.5639173157 4.6998757286 152.664961
34.086 2018-05-25.076 15:11:45.076 2018-05-25.076 15:11:27.076 0.911 1.915 159.244 50.5639149000 4.6998738000 153.427 DIFF 15 50.5639173096 4.6998757775 152.665784
34.130 2018-05-25.120 15:11:45.120 2018-05-25.120 15:11:27.120 0.911 1.915 159.243 50.5639149000 4.6998738000 153.427 DIFF 15 50.5639173097 4.6998757771 152.665762
34.174 2018-05-25.164 15:11:45.164 2018-05-25.164 15:11:27.164 0.908 1.913 159.243 50.5639149000 4.6998738000 153.427 DIFF 15 50.5639173104 4.6998757708 152.665634
34.218 2018-05-25.208 15:11:45.208 2018-05-25.208 15:11:27.208 0.909 1.914 159.244 50.5639149000 4.6998738000 153.427 DIFF 15 50.5639173112 4.6998757645 152.665505

Reach
% (lat/lon/height=WGS84/ellipsoidal,Q=1:fix,2:float,3:sbas,4:dgps,5:single,6:ppp,ns=# of satellites)
% GPST latitude(deg) longitude(deg) height(m) Q ns sdn(m) sde(m) sdu(m) sdne(m) sdeu(m) sdun(m) age(s) ratio
2018/05/25 15:11:45.000 50.563908231 4.699875495 200.2006 1 6 0.0153 0.0074 0.0153 0.0073 0.0048 0.0029 0.99 999.9
2018/05/25 15:11:45.200 50.563908257 4.699875534 200.1999 1 6 0.0150 0.0073 0.0150 0.0072 0.0047 0.0028 0.19 999.9
2018/05/25 15:11:45.400 50.563908179 4.699875521 200.1940 1 6 0.0150 0.0073 0.0150 0.0072 0.0047 0.0028 0.39 999.9
2018/05/25 15:11:45.600 50.563908223 4.699875531 200.2013 1 6 0.0151 0.0073 0.0151 0.0072 0.0047 0.0028 0.59 999.9
2018/05/25 15:11:45.800 50.563908226 4.699875495 200.1909 1 6 0.0152 0.0073 0.0152 0.0073 0.0047 0.0029 0.79 999.9

[Amilcar_Lucas]

You are comparing WGS84 altitude with MSL altitude. Those are different. Google is your friend here.

[Shaun_Bell]

Check the difference between your ellipsoid (wgs84) to your Geoid height. WGS84 isn’t much use when surveying : ) This is a great one hour tutorial: https://coast.noaa.gov/digitalcoast/training/datums.html