[Baron]

Anyone used Memory Maps on iphone/smartphone (e.g. HTC)? http://www.memory-map.co.uk/gps.htm

I need to log the location (GPS/grid ref and elevation) of single features to within a meter and present this info as a map on the web.

Or should I just buy a Garmin?

Cheers

[Jim]

gps isn't accurate enough

[Johnny Brown]

GPS will be more accurate than any other way of doing it.

[Paul B]

(including levelling?)...

I did note that GPS based levelling systems require you to leave them in place for hours to get an accurate fix and even then they're within tolerances of manual levels. Recently Nat had some levelling done of an old masonary spillway and the accuracy from the previously recorded levelling data was astounding.

[underground]

El Barone, I've got a spare garmin vista you can borrow if you want. Send me a pm like

[Baron]

(including levelling?)...

No need to level an area, just a single reading. The features are generally remote, so establishing a datum (levelling back to the nearest benchmark) could be tricky - especially on my own.

Another method could be to cross ref location with existing contour information, but that would require accurate location data.

QED.

Underground, I have PM'd you.

Cheers for the responses.

[Jim]

what phone have you got?

[tomtom]

I've done quite a bit of work on this, and if you want to go back and discover the exact spot within a metre at another time - then you're not going to be able to do it without using Diffferential GPS of some sort. Multiple readings at one point will improve the accuracy but only up to a point.

We've done alot of work using cheap GPS units and not seen any real difference compared to the expensive ones. you may well find that the one in your phone is fine. If you want to get back to an exact point then you're going to have to use either DGPS or some other form of surveying - and tie that into local bench marks.

As an alternative, if you mark (somehow) the point you need then a normal GPS will probably get you close enough to spot it. I've done this in the field before - been looking for erosion pins on a grassy hillslope and you know roughly where they are then have to grub around for them.

[Baron]

My current phone is 6 years old and basically clockwork.

Considering a new smart phone and thought I might be able to save on buying a separate GPS too.

Some background. I will be mapping the location of prehistoric rock art/carvings in the Peak, like this:

http://www.stone-circles.org.uk/stone/gardomsedgerock.htm

I completed my archaeological training 13 years ago and survey techniques have moved on since then.

DGPS is now generally used in most archaeological survey work (e.g. setting out trenches or grids), and although I would only be recording a single location it makes sense for the way I do this to be both compatable with, and of comparable accuracy to, current research standards.

I'm in contact with my old department in Sheffield so there's a chance I may be able to borrow some kit from them.

If not, tomtom, any advice on DGPS units?

Cheers

[Jim]

gps is owned by the american military and they can turn the accuracy up or down as and when they want. there is a european positioning satalite that when up and running will be accurate to a few cm, a year or so off yet. no idea about dgps

[tomtom]

I'm in contact with my old department in Sheffield so there's a chance I may be able to borrow some kit from them.

If not, tomtom, any advice on DGPS units?

Thats your best bet - last time we bought one (3-4 years ago) it was about £10k.. You can rent them thought... prob c. £200 for the day I would imagine...

If its mapping the location of boulders/artefacts/locations then GPS is probably fine - its a case of getting you within a few m of the site. if its (for example) multiple features on one rock or within one area then it may be trickier...

Can you see the features on Google earth/maps? If so you could get the location from there (though there are some issues about how well geo-referenced that data is...)

[Baron]

Thumbs up for the project from the Peak Parks head archaeological honcho.

And sourced one of these bad boys from a mate:

http://www.trimble.com/geoxm.shtml

Thanks for the advice ya'll

[Ena]

We use those handheld Trimbles at work, easy to use and pretty accurate. For your needs that should do it. We also have the 'big trimble' for centimetre accuracy, but at over £25k each and the size of a hat stand not really one to take on the sly.

I also use MemoryMap on my own HTC windows phone and really rate it. If you do want to get a new phone I'd definately recommend it. You'd need lots of storage space for maps though. And a waterproof case.

Look forward to the results!