Recommended GPS for marking tree locations

[jtheiss]

Hello,

I have been looking at buying a gps unit to mark future tree locations for a project with a park department. I figured that this site is a wonderful place to find passionate and knowledgeable folks that really understand the technology out there. I am very unfamiliar with gps units and had some basic questions.

 

I need something that can be accurate within to 2-3 feet and is not super expensive-$150 range

Is the info i mark easy to share with others?

Which devices have short battery life?

Anyone want to sell me a used one that is reliable?

What is devices/features are recommended not recommended?

 

I am helping the parks department mark tree locations for a passive/active park that was recently largely demolished. The park was designated as a flood control area and now has a large pond and dam which is great, but many trees were lost to build the pond.

 

Thanks,

John

[+Chief301]

Just about any handheld GPS, regardless of price range, will perform the very basic function of marking a waypoint. The higher end just gets you a lot of nice bells and whistles, which could be gravy for a dedicated Geocacher or hiker, but probably not necessary for what you want to do.

 

However, that 2-3 foot accuracy is a lot to expect. Consumer grade GPS receivers just aren't that precise. Experienced Geocachers know not to expect anything better than 10-15 foot accuracy, and that's assuming that the person listing the coordinates was meticulous about getting several readings, on a few different days, and averaging the results. Just clicking "Mark Waypoint" won't get you even those results.

 

Sometimes we get lucky and the reported coordinates are within 2-3 feet, but it's not the norm.

[+Bear and Ragged]

I need something that can be accurate within to 2-3 feet and is not super expensive-$150 range

AS per post above. Not going to get that kind of accuracy.

 

Is the info I mark easy to share with others?

You can save the waypoint and name/number it. It's saved as a GPX file, which can be plotted on a map.

Or printed to show the co-ordinates.

 

Which devices have short battery life?

Long battery life? Or is it that you want to avoid the ones with short life?

You could always use rechargeable batteries, and if you're out for the day it never hurts to carry a spare set of batteries. Most units should give you a days worth of use.

[jtheiss]

Thanks for the replies. Any additional replies are appreciated. I suppose i can mark the locations with flags or stakes and then mark with a gps. In past park projects, i have found that kids will pull flags and stakes and i am trying to avoid duplication of duties.

 

How expensive are the gps units not considered consumer grade?

 

Thanks folks,

John

[+Chief301]

For a device with greater than consumer grade accuracy, you would expect to pay at least a couple of thousand to several thousand dollars. Now you're getting into the kind of stuff professionals (surveyors and engineers and such) use.

[+Gitchee-Gummee]

You probably won't want to buy a professional-grade unit, unless you are a surveyor or somebody else with training and expertise to make a living off of the darn thing. They are that expensive.

 

Most any current crop of consumer-grade device will do what you want within reason. Expect to lay out $200+ for a decent one. Cheaper is what you get... cheaper. You can take multiple readings over days, average them and be pretty darned accurate. The trick is... don't hurry your job. Take your time and do it right.

 

As far as marking trees... you could use a self-sealing metal band with the necessary data on a dog tag-type plate. Sealing the metal band around a branch would be better than flagging or actually nailing something to the trees. Check in nursery supply places, or even landscaping services.

[+DazeDnFamily]

I think he's looking to make a point shape file of places trees will go at some point in the future, unless I misread this. If that's the case, you might be better off to see how current the imagery in Google Earth is, and build a kml. Any modern mapping application should be able to ingest a kml, and if I'm not mistaken, GE will export the points as a CSV, or possibly even a shape file, which every mapping app on Earth will use. And, GE is free, and in most places, reasonably positionally accurate. (Again, short of having a professional surveyor derive the coords, your accuracy is going to be limited.) If you're going to use a GPS to derive the points, you should be able to export them in a format a mapping application can use. Also, you might see if a local surveyor would be willing to do pro bono work for the park, or maybe if there's a tech school that teaches surveying nearby that needs a field project. Or, use the trusty can of rustoleum to mark spots.

 

Best of luck!

[skweetis]

Hi, sounds like a cool project. If the data you collect are going to be used for any sort of park planning, landscape design, trail building etc you're going to want the accuracy you're stating (2-3') or better.

 

Bad news is that your budget is about 5k shy of what's needed to get you a device like this with the software needed to process the data. Good news is that you can easily rent a unit that'll collect what you're looking for. There are lots of outfits that rent these by the day and will ship them to you.

 

I'd suggest you rent a Trimble GeoXT (1m accuracy postprocessed) or GeoXH (10-50cm postprocessed) for a day, collect everything, process it and export it in a few formats, probably DWG/DXF (CAD), Google Earth and ESRI shapefile. You can always convert later but it can save you a future headache unless you're certain of the software you and others will use.

 

I'm sure there are other brands, but Trimble is by far the most commonly used by pros. You can rent for a day with your budget and collect data like crazy. Make sure the rental place includes a temp license for Pathfinder Office so you can postprocess your stuff.

[mikkyberten]

I really like the concept. It would be so nice to have all the places in one input. Currently, my friend is working on synchronizing Motion sensor security lighting with GPS. It would locate the location of the vehicles and accordingly it would control the lights.