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How accurate is accurate enough?

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Just out of curiosity, how accurate is accurate enough?


I have been reading various posts (mainly LinkedIn) etc on GIS and GPS location services etc and it is very easy to be seduced (if I can use that word) at the thought of using our mobile phones to record our locational details.


Is 3-5m accurate enough?

  • In terms of telling us where we are - probably.:001_smile:

  • In terms of indicating a tree - arguably yes.:confused1:

  • In terms of recording the tree location- arguably not :thumbdown:

  • In terms of recording the tree location to be used as a future positioned asset- defintely not :w00t:


However, is using smartphone as a positional locator any better than marking on a map from 10 yeras ago? Or recording an offset from a street light? or corner of a building?


Personally, I fear that we building a huge data correction time bomb using smartphones as accurate positional instruments - one that cannot be easily diffused. (profund)

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The organic nature (pun intended) of this profession and it's charges and surroundings means there cannot be a perfect system.

A GPS location backed up with a 360deg picture and a Transponder in the target tree would be about as good as it gets...but nothing is infallible if someone wants to beat the system.

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The only time I’ve needed accurate GPS is on large scale local authority safety surveys or utility surveys where topographical plans or detailed OS maps are unconventional and time consuming (both in the field and when importing into a report). Sub 1m or sub 0.5m accuracy is required for these surveys I think. If you’re lucky enough to get these contracts you can work the price of an accurate GPS hardware into the cost – however, when I have done such surveys I’ve always been supplied with both the software and the hardware by the client, as the data produced fits in with the systems they already use.


If I could afford an accurate GPS device I would love to buy one but for the majority of my surveys a detailed OS map or topographical plan and a reliable data recording device, such as smartphone or PDA is sufficient. But I don’t think sub 10m GPS you generally get on smartphones is accurate enough for large scale inventory surveys.

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If you want to record position that accurately, and only have a smartphone, then record what the smartphone says and put the coordinates in googlemaps to get roughly where you should be. Then look at the aerial picture, find what you want on there, centre googlemaps on that and read off the proper coordinates.

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Can't you just triangulate it from the position of 2 sheep? That's how we navigate on Dartmoor. Takes human error out of the equation.

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