[CANUFNET] High precision (+/- 10cm) tree location

[Julian Dunster via CANUFNET]

Anything is possible with regard to GPS accuracy. Pay enough money and 
spend enough time and you can get within a few millimetres of reality. 
But what does the assignment require? If it only needs to locate trees 
to a point where  you clearly know location relative to street address 
then plus or minus 1 metre is likely to be good enough. If you require 
determination of ownership relative to a property line you will need a 
licensed surveyor not a GPS coordinate. There is a big technical and 
legal difference between map grade plans and survey grade plans.  For 
routine inventory work I think plus or minus 1 metre is likely enough, 
but remember to locate to the centre of the trunk so that all plots have 
that centroid correctly located. Figure out what the data will be used 
for and that should help to determine what level of accuracy is needed. 
You can spend a lot of money collecting unnecessarily accurate data that 
is irrelevant to the decision making process.

You also need some knowledge about the equipment being used, and what 
filters it has for use and if they are on or off. For example what is 
the PDOP set to? What is the minimum azimuth for signals low on the 
horizon? Which geoid is applied, which coordinate system is used (In 
Canada typically UTM and NAD 84),  and what tolerance is allowed on 
multipath errors?   GPS data is very sensitive to GOGO. Garbage in = 
garbage out.

It is amazing technology. I suggest taking a training course for GPS 
data collection to learn more. And then work out what data standards are 
required in a province or municipality.

On Behalf of Dunster and Associates Environmental Consultants Ltd.


Dr. Julian A Dunster R.P.F., R.P.P.., M.C.I.P., ISA Certified Arborist,
ASCA Registered Consulting Arborist # 378,
ISA Tree Risk Assessment Qualified
Honourary Life Member ISA + PNWISA

North American distributor for Rinntech
www.dunster.ca
www.treelaw.info

On 11/5/2018 10:30 AM, Maurice, Jerome via CANUFNET wrote:
> Hi Canufnet,
>
> I came across a recent discussion about tree geolocation tools used by some urban foresters (see below). Based on practical experience, is anyone able to recommend one or more devices that are highly accurate (+/- 20cm) for tree inventory ? what would be a reasonable target under closed canopy cover (20cm ? 50cm ? 1m ?)
>
> Thanks a lot.
>
> Jérôme Maurice, Ing.f. M.Sc.
>
>
> -----Message d'origine-----
> De : CANUFNET [mailto:canufnet-bounces at list.web.net] De la part de Art Maat via CANUFNET
> Envoyé : 19 janvier 2017 17:35
> À : Marie-Hélène Sauvé; Canadian Urban Forest Network
> Objet : Re: [CANUFNET] tree protection
>
> Mobile software is available from Histree for plotting and or surveying tree locations with species, condition, images and other variable attribute data in field.
>
> As well GPS hardware is available and can connect to Android or iOS devices via Bluetooth resulting in sub meter accuracy point locations.  Additionally using Histree and on board satelite views a user can also visually reference a location by moving the map while the pin is stationary. Much like Uber interface.
>
> Regards,
> Art Maat
> 780-937-4056
>
>> On Jan 19, 2017, at 3:08 PM, Marie-Hélène Sauvé via CANUFNET <canufnet at list.web.net> wrote:
>>
>> Hi there,
>>
>> Just to adjust something about GPS and urban forestry: there exists many
>> types of devices that are accurate enough (+/-10cm precision) to make a very
>> good distinction between two trees located nearby (and even the property -
>> if it's a public tree or not). Those devices are way more expensive than
>> those easy-to-use Garmin or other GPS device used traditionally in forestry.
>> Those high-level precision GPS are used by some consultants in the Greater
>> Montréal. So YES, it may be used and applied. The user has to know how to
>> use it properly though; GIS skills are required!
>>
>> Cheers,
>>
>> Marie-Hélène Sauvé
>>
>>
>>
>> -----Message d'origine-----
>> De : CANUFNET [mailto:canufnet-bounces at list.web.net] De la part de via
>> CANUFNET
>> Envoyé : 19 janvier 2017 13:12
>> À : jd at dunster.ca; Julian Dunster; Michael Richardson; Canadian Urban Forest
>> Network
>> Objet : Re: [CANUFNET] tree protection
>>
>> Unfortunately GPS is not accurate enough to plot trees, especially when
>> landmarks that are accurately located by a surveyor aren't close by (i.e. a
>> forest or large natural area).  GPS's currently available don't have the
>> resolution to separate two trees that are 2 feet apart, or may be on the
>> other side of a property line with 100% accuracy.  A critical point. It's a
>> help but not the solution, yet.
>>
>> CAD and GIS are great for plotting the data (we use both) but the locations
>> need to be accurate to start with. The days of drawing-in a dot by hand on a
>> site plan are gone.
>>
>> Stephen Smith
>> ISA Certified Arborist, Urban Forester
>> Urban Forest Associates Inc.
>> -----Original Message-----
>> From: Julian Dunster via CANUFNET
>> Sent: Thursday, January 19, 2017 11:56 AM
>> To: Michael Richardson ; Canadian Urban Forest Network
>> Subject: Re: [CANUFNET] tree protection
>>
>> Many of arborists in Britain regularly use GPS, GIS, and CAD routinely for
>> development projects. One of them developed special CAD software for the
>> purpose. The lack of its use in Canada almost certainly reflects a lack it
>> being taught in curricula, as part of professional practice. We still focus
>> on pruning, planting, fertilising and tree stuff, all of which is fine but
>> needs expanding to the 21st century to include effective use of technology.
>> Several of my colleagues in BC use CAD all the time. I use GPS and GIS.
>>
>> We need to expand the horizon of what arboriculture and urban forestry might
>> / should entail. At the same time we can also inform surveyors and
>> architects of we expect them to produce - such as CAD symbols for canopy
>> that are scaled to reality on the ground, not simply rubber stamped on a
>> plan, all at the same size (a pet peeve).
>>
>> On Behalf of Dunster and Associates Environmental Consultants Ltd.
>>
>>
>> Dr. Julian A Dunster R.P.F., R.P.P.., M.C.I.P., ISA Certified Arborist, ASCA
>> Registered Consulting Arborist # 378, ISA Tree Risk Assessment Qualified BC
>> Wildlife Danger Tree Assessor Honourary Life Member ISA + PNWISA
>>
>> North American distributor for Rinntech
>> www.dunster.ca
>>
>>> Some interesting thoughts here.
>>>
>>> Those little dots; most arborists I know do not have the equipment or
>>> expertise to to locate trees with any precision, nor the GIS software
>>> to plot them.  If an arborist is using a plan created by a surveyor
>>> than surely the arborist must locate and plot not the tree, but the
>>> entire trunk diameter or root collar/trunk flare with the same
>>> accuracy and precision.
>>>
>>>
>>>
>>>