Adding Higher Accuracy to an SP20
can add additional accuracy to the SP20 at any time. There is no
price penalty for purchasing a base unit, then adding accuracy at a
However, you will want to purchase the
final accuracy that you need because there is no intermediate step.
If you purchase ‘Sub
Meter 30-30 $1,500’ and then at a later date decide to purchase
the ‘CM $5,100’ you will have wasted $1,500: there is no option
to go from '30-30' to 'cm'.
this reason, if you are not sure about which accuracy you would like
to purchase, we strongly recommend that you ‘rent’ an accuracy for
1-month. The monthly rental price is 10% of the full option price.
If you plan on using
an RTX Subscription (about $2,000 per year) you do not need to
purchase any additional accuracy options. When RTX is activated, the
SP20 will achieve maximum RTX accuracy no matter which accuracy
option is enabled.
This means that the
base SP20 model will be just as accurate using RTX as the 1 CM
The expected accuracy
of the SP20 using RTX corrections in the USA is 4 cm CEP.
The advantage of RTX
over a RTK network is: 1) no cellular connection is required; 2) it
works nationwide. A possible disadvantage of RTX is the convergence
time (probably about 20 minutes); this is the time from when the
receiver starts getting L-Band corrections until the stated accuracy
information on RTX click [
RTX Information ]. A
one-time, 3-day RTX demo is available [
RTX Demo ]
There are two
post-processing options. The first option:
680547-51 Post processing option for MobileMapper Field Android
enables raw data
recording in MobileMapper Field. It is installed with a single use
POPN code on the receiver and is attached to the receiver. This raw
data is un-dithered and can be processed in MobileMapper Office.
The free version of
MobileMapper Office will process raw files to decimeter level. The
116128-01 MobileMapper Office cm post-processing option 895.00
office to post process down to 1 cm accuracy. This option is applied
to a single office machine with a unique POPN code and is not
SBAS (WAAS) Expected
and Observed Accuracy
The standard receiver
with no accuracy enhancement options enjoys the legendary Blade SBAS
engine. The SP20 engine is specified as producing 50 cm horizontal
2Drms and 85 cm vertical 1-sigma results using EGNOS/WAAS. It is our
experience that the Blade engine has much better performance in the
United States using WAAS than can be obtained in Europe using EGNOS.
performance is not dithered by the accuracy option. So if you are
only going to use WAAS corrected readings, you should not purchase
the higher accuracy options.
Using our testing
robot in moderate urban canopy [
with WAAS corrections
set to dump the receiver, then wait 30-seconds for signal
acquisition, then storing a single epoch reading, we repeatedly get
results like this:
Over a 264-minute (4
hours 24 minute) period, encompassing 316 dump cycles, the receiver
had a 0.266 meter 1-simga 2D horizontal deviation about the average
position. In other words "we expect the two dimensional, horizontal
error to be within 0.266 meters, 68% of the time."
Over this same
testing period a total range of 1.38 meters in the X, 2.70 meters in
the Y direction; or +/- 1.6 meter horizontal range about the average
location was observed. The height standard deviation was 0.74 meters
with a range of 3.9 meters.
Remember that this is
a full signal reacquisition between measurements in moderate urban
canopy with a 30-second acquisition time allowance which is
representative of real-world use. The SP20 will have substantially
better results in wide open conditions, however wide-open testing is
not representative of the results you can obtain in real-world
Also remember that
when using WAAS corrections, the reported position is IGS08
This is slightly
better than we would expect with the CHC LT500T or the legacy
Spectra Precision MobileMapper 120 receivers. For reference, this is
about 8 to 10 times better than we observe with the built-in GNSS
receivers in modern cell phones.
The SP20 when enabled
for the best accuracy is a fully-featured multi-frequency,
multi-constellation receiver. The engine / antenna combination
achieves very fast fixes and has survey accuracy (1 cm) with a
Depending on the
accuracy option that is installed on the receiver, the accuracy may
be dithered about the true location:
The RTK reported horizontal position will be reliable to
1-meter. This is still better than WAAS because: 1) no reported
measurement will exceed 1-meter in error; 2) the result will be
in the same frame as the correction source, typically NAD83 2011
The result will be within 1 foot (peak-to-peak / maximum error).
The result will be within 0.23' horizontal and 0.07' vertical.
result will be undithered, full RTK accuracy.
The SP20 has
Flying-RTK enabled. This means the SP20 will have amazing results
with very long baselines. (Baseline is the distance from the
receiver to the source of corrections.)
For example, a
fully enabled SP20 located at our office in Salt Lake City receiving
RTCM3.0 corrections from the CORS station in Kemmerer Wyoming (165
KM) typically has measurement range results like these:
X Avg 427442.023 Min 427441.958 Max
427442.127 Rng 0.169 StdDev 0.030
Y Avg 4509830.987 Min 4509830.906 Max 4509831.073 Rng
0.167 StdDev 0.022
dXY Avg 0.032 Min 0.008 Max 0.132 Rng
0.123 StdDev 0.020
H Avg 1310.185 Min 1310.016 Max 1310.633 Rng
0.617 StdDev 0.096 N 5723
consecutive measurements (1 hour 30 minutes) the 2-D CEP (1-sigma)
is 2 cm with an absolute range of 0.125 meters. This means that a
single CORS station can service 100 mile radius area with a 1/2 foot
expected range of measurements.
Base/Rover Pair: Since the SP20 does
not have the ability to be used with a UHF radio, the SP20 is
unsuitable for use in a Base / Rover pair configuration. While it is
possible to push Base corrections to a internet server a cellular
connection will always be required for SP20 RTK use.
Traditional Survey Applications:
The available Android
survey solution (Survey Mobile) may not be as full featured as other
WinCE and Win10 survey applications. Integrated support may not be
available for robotic total stations and peripherals. Because you
can evaluate the Spectra Survey and MobileMapping applications on
any Android device, it is easy to verify features and workflows
prior to purchase.
simultaneously fills several segments of the mobile-mapping/GIS and
survey GNSS toolset. The base unit is as accurate as any other GNSS
based, WAAS corrected instrument at a better price-point. Because
the data-collector is built-in to the SP20, when fully enabled for
the highest accuracy the SP20 competes well with traditional GNSS
survey instruments at a better price-point.