Are some GPS's better under tree cover or are they all fairly useless. I have a base model Garmin Etrex and would love to have coverage when trails go into forest but alas....
Hope you have some suggestions.
GPS under trees
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Map Monkey
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Hi Martismo,
You must remember that the base model Etrex was originally released in over 7 years ago IIRC and as such is considered old technology (even though they still work OK and are used by many) in comparisons to some of the newer SiRF III chipset models etc.
I find that the newer SiRF III chipsets models will hold the signal for much longer and in lots of cases, continuously, when under tree canopy than the yellow etrex's. Remember that the water content in and around the tree, especially the leaves, is the problem with GPS usage under canopies and as such i find the signal will hold for much longer in the afternoon (allows leaves to dry) and in the drier months.
I normally tend to record tracklogs and waypoints for future reference in Search and Rescue towards September/October as there has been a relatively (well for up North 
) dry period and walk the tracks late afternoon which also makes for great sunsets. 
The other thing to remember is that the GPS will track better when it still has a signal rather than trying to re-establish a signal. I find it ideal to establish a strong signal before going into less-than-ideal signal areas, and will wait some time (5min +) before continuing. Many people will only turn their GPSr on AFTER getting to their GZ and find that they cannot obtain any signal in most cases. Better to turn it on BEFOREhand, and hold the GPS unit for optimal reception (horizontal in your case) whilst traversing these areas.
mm
You must remember that the base model Etrex was originally released in over 7 years ago IIRC and as such is considered old technology (even though they still work OK and are used by many) in comparisons to some of the newer SiRF III chipset models etc.
I find that the newer SiRF III chipsets models will hold the signal for much longer and in lots of cases, continuously, when under tree canopy than the yellow etrex's. Remember that the water content in and around the tree, especially the leaves, is the problem with GPS usage under canopies and as such i find the signal will hold for much longer in the afternoon (allows leaves to dry) and in the drier months.
I normally tend to record tracklogs and waypoints for future reference in Search and Rescue towards September/October as there has been a relatively (well for up North ) dry period and walk the tracks late afternoon which also makes for great sunsets. The other thing to remember is that the GPS will track better when it still has a signal rather than trying to re-establish a signal. I find it ideal to establish a strong signal before going into less-than-ideal signal areas, and will wait some time (5min +) before continuing. Many people will only turn their GPSr on AFTER getting to their GZ and find that they cannot obtain any signal in most cases. Better to turn it on BEFOREhand, and hold the GPS unit for optimal reception (horizontal in your case) whilst traversing these areas.
mm
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sirius Tas
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gps under trees
Hi Martismo,
As a surveyor for Forestry Tas have been using GPS for over 10 years...what Map Monkey has said is 100% correct.
Get your GPSr receiving before you enter under canopy...what you need to bear in mind is that when a GPSr first fires up it has to hold lock on individual sats for approx. 30 seconds each which is far easier out in the open...but once lock is obtained and GPSr kept on it can lose lock and regain lock whenever it gets a strong enough signal.
Also spot on re wet canopy...GPS signals wont penetrate wet canopies as easily and if near radiata pine...forget it if wet..totally useless even with high end GPSrs.
Cheers
As a surveyor for Forestry Tas have been using GPS for over 10 years...what Map Monkey has said is 100% correct.
Get your GPSr receiving before you enter under canopy...what you need to bear in mind is that when a GPSr first fires up it has to hold lock on individual sats for approx. 30 seconds each which is far easier out in the open...but once lock is obtained and GPSr kept on it can lose lock and regain lock whenever it gets a strong enough signal.
Also spot on re wet canopy...GPS signals wont penetrate wet canopies as easily and if near radiata pine...forget it if wet..totally useless even with high end GPSrs.
Cheers
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Team Wibble
- 2100 or more geocaches found
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I have to agree. I don't know what chipset the foretrex uses either, but on several occasions where we've had that and a yellow Etrex, the foretrex consistently gets better reception, especially under cover.richary wrote:I don't know what chipset the Foretrex (wrist mount one) uses, but it seems to hold the signal better than the eTrex under tree cover.