User manual

Maximum Hdop Hdop is a measure of GPS accuracy. A value of 1.0 is

perfect, a value of 10.0 is poor. This setting sets the

maximum value of Hdop at which ViewRanger will consider

the GPS reading valid. If the Hdop reported by the GPS

module is above this value then the GPS circle and cross

will go grey, and no track points will be recorded until the fix

is more accurate.

Position timeout If your GPS stops telling ViewRanger its location

ViewRanger will wait a short period before changing the

GPS indicator to invalid. This item sets that time period. At

the default value of 15 seconds ViewRanger would wait 15

seconds before greying the GPS symbol.

Use check sum This is an advanced setting, which tells ViewRanger to

perform additional checks on the GPS data it receives. It is

normally left off but if you had GPS reliability problems you

would switch it on. It is only available on 2

edition phones.

GPS Accuracy & Headings

Even the best GPS units give small errors. Most units are accurate to plus or

minus 10 metres, though some can be as accurate as plus or minus 2 metres.

Their accuracy falls if they have a limited view of the sky – for example if you

are under trees or by the side of a cliff.

Every reading that the GPS receiver takes is subject to the errors, so the GPS

does not know when you are standing still because its readings still show some

fluctuation. To overcome this ViewRanger only uses the GPS heading when the

speed is more than a tolerance. For an accurate GPS a tolerance of 0.5km/h

would be good, but for less accurate devices a tolerance of 1.5km/h is more

appropriate. ViewRanger can also average successive heading readings to

smooth out the small GPS errors.

Stationary Speed

Stationary Speed sets the lowest GPS speed at which you are considered to be

stationary. If you are stationary then ViewRanger does not update the heading

until you start moving again. So if you walk north, stop and turn around to face

south, the heading given by ViewRanger is still North.

If the Stationary Speed is set to 1.5km per hour, then ViewRanger will consider

you to be stationary if the GPS receiver reports a speed of 1kmph, but moving if

it reports 2kmph.