Best GPS?

[kevin wooldridge]

Agree with Oxbeast and Sheep ..........but would caution against using a hand-held GPS to establish levels. I would urge that you consult the fantastic facility that is the Ordnance Survey. There is nowhere in the UK that is unmapped and you might be surprised at what the OS can offer in terms of benchmarks and location points in 'remote upland areas'.

[BAJR]

HAve been working all day on the Croatia Project GIS... and thought this may interst you.. showing you how you can use a Garmin handheld and get good results... as long as you know where you are (thanks Googlemaps! )

I rectify the googlemaps using OziExplorer and QGIS. then plot my Gps tracks.. (blue lines) which represent the walls I walk. I am then able to 'correct' it to the real location (the orange lines) job done... the acuracy is out by quite a bit, but not so bad I can't recognise where I am... so am now a happy puppy! I save each track (site number) and then clear the tracks and record the next track/wall/ it seems to work well.

have a look - and yes I am still working on teh QGIS for archaeologists... there are others who are far more advanced than me,..... and a local group called CRISP... I will be talking with them about a toolkit. (opensource) along with my own partnership Digital Past (we do things like Open Archive and the Bute website)

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[sheep]

It strikes me that a cheap handheld GPS is the new sat nav, (or before that the calculator). We're in danger of relying on the "easy" new technology to the detriment of common sense and basic skills. Going back to trench locations for example. Where is the excuse for that in a field with clearly mapped field boundaries?

[BAJR]

In a way you are right, where the old ways are sometimes best... Like being able to set out a grid and tie it in to the National Grid without the need for a micro mm accuracy GPS system... All technology should be used to aid ... not supplant.

[kevin wooldridge]

I absolutely agree with your last comments David.

My fear is that the technology represented by GPS starts to become the end result rather than GPS being used as a tool. I personally think that the traditional archaeological methodology in the absence of fixed survey points of starting from the smallest and working up i.e first link your feature/find to a grid, then link your grid to a site boundary, then link your boundaries to local topography, then link your topography to the National Grid is still the most efficient and accurate practice. More importantly it was one that everyone could understand and work with.

I fear that technology could create a class of archaeology techno-geeks who are happy to hide behind their machines and 'pretend' there is something more complicated to what they do than there actually is. Or even worse imagine that technology can replace time tested methods. It can't. It can only help competent archaeologists use their time and resources more efficently....and I know. I am one of those geeks (but one who still has time and respect for the 'old' ways ....a 'techno-druid' maybe....!!) ... and also I have just heard today, one who is about to forego my trusty Leica for a crash course in Trimble technology....I'm scared!!

[Dinosaur]

....My fear is that the technology represented by GPS starts to become the end result rather than GPS being used as a tool. I personally think that the traditional archaeological methodology in the absence of fixed survey points of starting from the smallest and working up i.e first link your feature/find to a grid, then link your grid to a site boundary, then link your boundaries to local topography, then link your topography to the National Grid is still the most efficient and accurate practice. More importantly it was one that everyone could understand and work with....

On the basis that I'm lucky to see a surveyor once a week with the modern state-of-the-art mega-bucks thing on a stick, there's no danger of the old string, randomly stretched tapemeasures and tripping-over-gridpegs techniques dying out in the foreseeable future. On the plus side, at least any fixed points I've left don't all need to be (ideally) intervisible any more. Also it's a good way of spotting that members of the workforce haven't mastered the basics of the optical level... :face-approve:

[Jack]

You can increase the accuracy of you readings by taking lots of the same point, then averaging them.

Also having more surveyed in referance points can help you jiggle the position for a better fit, if you got CAD and the digital map data. The more you do this, the more accurate it will be.

I once helped a friend plot a readings from a hand-held GPS against time. Very intersting result, from what I remember it varied as a simple sine curve! But that was back in the day when the signal was scrambled.

[Jack]

HAve been working all day on the Croatia Project GIS... and thought this may interst you.. showing you how you can use a Garmin handheld and get good results... as long as you know where you are (thanks Googlemaps! )

I rectify the googlemaps using OziExplorer and QGIS. then plot my Gps tracks.. (blue lines) which represent the walls I walk. I am then able to 'correct' it to the real location (the orange lines) job done... the acuracy is out by quite a bit, but not so bad I can't recognise where I am... so am now a happy puppy! I save each track (site number) and then clear the tracks and record the next track/wall/ it seems to work well.

have a look -

Hmm, not sure i understand what you've surveyed here. Is it boundaries, hedges, hollow-ways and earthworks?
Wouldn't it save time to just rectify the google map, then trace off that?
How do you 'correct' your blue lines to the orange ones?

[BAJR]

[INDENT]Walls and tracks... big things that I can then relate smaller features too. However, the google map does not show everything.. ie gates, subtle changes beneath trees... so filed maps are also drawn (by hand) and by having a basic outline in the blue line... I can then shift everything to the 'correct location... and fit teh field plan (good old tape and paper) thus using th best of both worlds.

It's horses for courses basicly.. using the garmin in an area of tree cover to find myself... using teh paper and pen to draw what is there (plus a portable computer to log the sites onto a database while there) - However I suppose I can do this, being a surveyor who has used everything from the Theodolite to the Lieca GTS 1200 GPS understadning the principals to be ableto bend the laws of nature to fit what I need to do... and cheaper.

You'll have to buy the book... Survey made Shimples by J R BAJR [/INDENT]

[Jack]

Ah, I see now. Many methods make mistakes fixable.

Also coming from a science background I agree that the basic principles are the most important

'oh you have...thats marvelous, m-my name. Yes its........'