Magellan ProMark3 RTK Specifications download pdf (Page 239)

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ProMark3 may warn you if the PDOP, and therefore the accu-

racy, of your positions has dropped below the level you select-

ed during Setup (see page 240, the PDOP alarm option). If

you see this warning you may press the ESC button and con-

tinue logging.

However, if you are running a kinematic survey or recording

line or area features, you might want to return to the field

when the GPS satellites are in a better configuration overhead

(the constellation changes slowly but constantly).

And if you are running a static survey or recording a point fea-

ture, you should strongly consider moving to another location

with better satellite reception and recording an offset (dis-

tance and bearing) to the feature.

Quality Indicators

On the Survey Status screen in Surveying or at the bottom of

each logging screen in Mobile Mapping, you can see two num-

bers that give you a good indication of how accurate the

ProMark3 unit should be.

The first is the number of satellites that the receiver is track-

ing. In Mobile Mapping, a “W” will appear after the number

of satellites if SBAS is used. The presence of this letter is in-

dicative of an even better accuracy level.

The second number is the Positional Dilution of Precision

(PDOP), which is an estimate of accuracy that the receiver

constantly calculates using the geometry of satellites in the

sky. The more satellites that are being tracked and the more

evenly they are distributed around the sky, the better the ac

curacy. PDOP values less than 4 or 5 are good. If the PDOP

value is over 5, you should consider moving to an area with a

clearer view of the sky and recording features with offsets.

Tracking 3 satellites will in

principle allow you to cal-

culate a 2D position (lat/

lon) using the last altitude

recorded by the receiver.

You need to track at least 4

satellites to get a 3D posi-

tion (lat/lon/altitude). To

achieve the specified accu-

racies for ProMark3, you

will need to track 5 or more

satellites.

GPS quality indicators

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Magellan ProMark3 RTK Specifications Page 239

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