topic Re: GPS selection for underneath trees in ArcGIS Pro Questions

GPS selection for underneath trees

GlennJohnson — Sun, 13 Jun 2021 02:11:14 GMT

Hi All, I'm returning to ArcGIS Pro Advanced after 10+ years, and will be creating a map of my 7 acre property, including ~100 trees (wooded North facing slope).

Can I use my iPhone 11 Pro or an old handheld GPS unit under the tree canopies? I know the GPS signal is attenuated by the trees. i was hoping I could improve accuracy using my phone or handheld GPS by leaving the unit at each location for a minute or two, to improve the averaging of the GPS error.

If this is not the best plan to get coordinates for each tree, what is? Can i rent a professional surveying GPS that would work better?

Thank much!

Glenn on the California Central Coast

Re: GPS selection for underneath trees

ThomasHoman — Tue, 15 Jun 2021 01:56:43 GMT

Hi Glenn,

The question is not the case of if the device will work under the canopy but more one of what is the required accuracy. The iPhone 11 Pro does have a multi-constellation chip where the old handheld GPS may only be the US GNSS network. In the end, under a canopy the more satellites available the better. Your thought of position averaging via longer shots would certainly help.

One alternative could be the Ikegps Spike that puts a laser measuring device on your phone. Thus you can be out in the open and shoot to the trunk. https://spike.ikegps.com/ There have been several mentions in ArcNews.

Another alternative could be intersecting circles if your tree density is low enough to pull a tape measure around. If you set 2 or more averaged points you could pull a tape from the points to the center of the tree trunks. Back in ArcPro create a working feature class and create circles based on the distances measured to determine the location of the trees. We do this all the time in surveying as a distance-distance calculation.

I hope this helps.

Regards,

Tom

Re: GPS selection for underneath trees

GlennJohnson — Tue, 15 Jun 2021 03:01:51 GMT

Tom, excellent advice, thanks so much!

Assuming I make my iPhone work, any recommendations on apps to help easily log a hundred points, and assign tags / metadata categories for each? (Species, trunk Dia, condition, diseases)

It may be easier to generate all this on my phone than afterwards at my desktop computer. Perhaps ESRI has an app? Or something from the App Store?

thanks again!