GPS / PDA / Data Capture?

[Paul Barton]

Just an update - I came across this article which discusses a submetre GNSS receiver specifically for those of you using iPad/iPhones Geneq Introduces Sub-Meter GNSS Receiver for iPad, iPhone : GPS World

 

I don't have either so I've not spent much time looking into this, but its currently in the states and should be either released over here or possible to direct import.

 

Adam M - how did you get on with Pear Tech? I'm interested to know. I've also PM'ed you - could you check?

 

 

Thanks for the link, will look out for that on the market. Looks small enough to attach to a bag strap or something to keep hands free.

 

 

Sent from my iPad using Arbtalk

[daltontrees]

Thanks for the link, will look out for that on the market. Looks small enough to attach to a bag strap or something to keep hands free.

 

 

Sent from my iPad using Arbtalk

 

It probably has to be kept almost perfectly horizontal.

[10 Bears]

Recent experience suggests that GPS can't betrusted even when the signal is 'aged'. Surveying last week I established a location in clearing, then watched for 5 minutes as the cursor location (stated by the machine as HDOP 0.8m) wandered off across the clearing, into the trees, back into the clearing, across it and out the other side.That was with the Trimble immobile on a tree stump. According to the base map which had a hypothetical development layout on it, the sub-metre position had travelled 25 metres.

 

Just a thought Jules, but did you set up a planner for this survey using a satellite almanac? You may have had good numbers of satellites, but with unreliable signal. You still get a fix, but then the signal strength is a bit fuzzy.

 

I don't have the required software to check if this is the right link (it just opens as a text file without the software) - but Trimble put out an almanac every month that tells you when the best time of day is to be surveying. You may find you can survey from 8-11.30am as the satellites are spot on, then take a couple of hours off as they drop in efficiency, and then pick up again at say 13:30 when the heavens align and all is right with the world again. These optimum windows change each day and it can cause you lots of weak signal/location problems if you don't plan it out.

 

Anyhow the Trimble link is here: Trimble - GPS Data Resources Its the first link at the top of the page.

 

(Ive also PM'ed you Jules....)

[daltontrees]

Just a thought Jules, but did you set up a planner for this survey using a satellite almanac? You may have had good numbers of satellites, but with unreliable signal. You still get a fix, but then the signal strength is a bit fuzzy.

 

I don't have the required software to check if this is the right link (it just opens as a text file without the software) - but Trimble put out an almanac every month that tells you when the best time of day is to be surveying. You may find you can survey from 8-11.30am as the satellites are spot on, then take a couple of hours off as they drop in efficiency, and then pick up again at say 13:30 when the heavens align and all is right with the world again. These optimum windows change each day and it can cause you lots of weak signal/location problems if you don't plan it out.

 

Anyhow the Trimble link is here: Trimble - GPS Data Resources Its the first link at the top of the page.

 

(Ive also PM'ed you Jules....)

 

I have repied to pms.

 

The GPS receiver in a Geo has an almanac, but when using PGIS you keep it switched off and PGIS activates the receiver using a different port and does whatever it needs to do to get you the best signal. It tells you te quality of the signal. If, youre using a base map you are just using that to get the right location and using the map to get the final position of the tree relative to physical features.

 

What's this thing about you can... 'take a couple of hours off'? Will do that next time, when Trimble or client pay me to take time off. If I told a client his survey report was late because of teh alignment of the skies, he'd think I was communing with Mystic Meg.

Edited May 22, 2014 by daltontrees

[10 Bears]

Its all a matter of efficiency!

 

In my opinion, there is little point trying to plot trees with >25m accuracy, when if you wait a couple of hours, you could perhaps get it back down to sub-metre. I just think it can be worth the wait sometimes...

 

And don't be dismissive of Mystic Meg - there's more powerful things in the cosmos then just you and I!

[daltontrees]

Then consider a Trupulse. Just need to get a couple of submetre definite positions on the edge of teh site then you can fire in every tree you can see to 10cm accuracy. And set up another position using it that gets you even further into the woods. No loss of time, super accuracy. No reading of tea-leaves or palms.