Satellite Channel 01

[4ndynorfolk]

I have noticed for a few weeks now that in the GPS Status screen, channel 01 does not turn red dispite being of good strength (above the second mark) and according to the diagram, almost ovehead.

As a consequence I often can't get better fix that 5m in open areas.

Has anyone else noticed this?

Is the GPS network operationg at less than full efficiency?

Exactly what does the diagram show - is up north?

[stevendunn99]

GPS status screen - I will check another time, but I think mine has been okay.
Accuracy - I sometime question it but recently I placed the device on a trig point and it was dead centre on the one on the map.

Map direction - it is North or your direction depending upon which you select, if that answers your question. I have no idea whether North is Grid north, true North or magnetic north but I am sure someone else here can confirm.

Steven

[M8TJT]

This is a really simplistic explanation. It ain't this simple really.

True North. The earth rotates about two points. The North and South poles (True North). True north is along any of the lines of longitude that join the North and South Poles. A compas device (NOT a magnetic compas) such as GPS or a fibre optic gyroscope device will be aligned to True North, and as such will 'point' to the true North pole and calculate bearings etc. as degrees east or west of true north.

Magnetic North. The magnetic poles of the earth are not situated at the real poles, but some distance from them. A magnetic compass 'points' to these poles, so there is (almost always) a difference between True and magnetic North (Magnetic Variation or MagVar). In the UK the magnetic pole is about 8 degrees West of True North, although it depends exactly where you are. The magnetic poles also move with relation to the True poles over a long period of time, so the MagVar varies with time, although this movement is is very, very slow. (Measured in tens of years).

Grid North. This is a line vertically from the bottom to the top of a printed map (grid line). Because you can't fit a curved surface onto a flat piece of paper, map makers have to make a compromise (projection) and align their maps such that the top of the map is in a northerly direction, but because of the projection, this cannot always be exactly True North as it varies over the extent of the map, especially ones that covers large areas.

The differences between True, Magnetic and Grid Norths can normally be seen on a decent map (OS, Nautical etc.) in one of the corners.

[stevendunn99]

[jonesbach]

[4ndynorfolk]

Thank you for your contributions.

Yes, I was refering to th ID number of the satellite. It seems likely that the wikipedia entry explains the problem.

My second question resers to the gps status screen also. Is up north in this screen? Thanks for the comprehensive answer in context of the map screen.

[jonesbach]

I have assumed North is up but have not searched sufficiently to be sure. A quick look produced this site which gives a short description of the status screen on the Garmin. I doubt if Satmap is any different.
http://www.gpsreview.net/satellite-info-screen/

[davidor]

I understood 5 metres (16ft) is as good as you will get with a stand-alone gps. To get better you either have to be a friend of the us military, or be linked directly to a fixed base station so that the induced drift can be negated. Which makes you wonder why the US military don't allow gps receivers to operate to much higher accuracy - surely their "enemies" have sussed out the system now.

[philpugh]

[FrequentFlyer]

Following on from this topic...what is generally the best settings advice if out up in the hills, (the Lakes) for the day, with the Lakes map installed....Grid North, Magnetic North ??

[lucevans]

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