onXmaps accuracy problems

[Loon]

Big fan of onXmaps, love the service but...
While researching water holes in my unit I found one that falls inside my unit when looking at onX but outside when I look at caltopo. When I emailed onX customer service to ask about it I got the below response from them.

"I took a look at the area in question and see what you are talking about. I have forwarded this to our mapping team and they will verify with the county. We will make all efforts to correct this in the next map update of your state! Let me know if you have any questions".

Anyone else have a similar issue? I've only been using the service for 2 seasons.

 

[rtraverdavis]

With that much data, there’s bound to be errors here and there. All the water sources I’ve noted in OnX were there when I checked them out in person, but none of those were on a boundary either.

 

[406LIFE]

Personally, I have not noticed any issues on boundaries in my time int MT, UT, WY, ID and WA. The most I have seen are boundaries that were drawn by rivers some time ago and the river has now shifted, but the boundary has not. If LEO's use it, I trust it.

 

[TheSurveyor]

I've seen some issues like this when you get around small parcels. Its built of free GIS data so... I'd say if you're getting into narrow areas spend the the time and verify

 

[BrentD]

I've seen some private lands (buildings and such) shown as public land. Makes me worry if I really can know where public stops and private starts.

 

[mtmuley]

I've seen some private lands (buildings and such) shown as public land. Makes me worry if I really can know where public stops and private starts.

What the Hell are you doing using technology? You just pick and choose? mtmuley

 

[BrentD]

What the Hell are you doing using technology? You just pick and choose? mtmuley

I do.

 

[mtmuley]

I do.

Me too. mtmuley

 

[RobG]

I've found places in MT where the property lines shown by OnX are off by hundreds of feet. I'm told this is a problem with the cadastral data, not OnX. I don't know how Caltopo gets their boundaries. Hunting districts usually follow geological features, roads, etc, and have precise descriptions in the regulations, so they should be easier to verify.

 

[Rzrbck918]

I’ve noticed it too. Where we hunt in New Mexico there are some private areas completely surrounded by forest and wilderness that are off by 300-400 feet. Not a huge deal for me but I understand if you were trying to thread the needle it could be an issue.

 

[Lonesome_God_outdoors]

What can be equally likely is the private/public fence is in the wrong spot. I personally know of ranchers who've moved fence to give themselves extra acres on their ranch. I also have a friend who owns a ranch that when originally surveyed was done incorrectly to the point where their ranch is 80 acres larger than the 640 they bought. It's been in their family for generations at this point though and the forest service either doesn't know or doesn't care.

 

[MTGomer]

I've found places in MT where the property lines shown by OnX are off by hundreds of feet. I'm told this is a problem with the cadastral data, not OnX. I don't know how Caltopo gets their boundaries. Hunting districts usually follow geological features, roads, etc, and have precise descriptions in the regulations, so they should be easier to verify.

You’re an engineer right? If you have some, have your surveyors explain this to you more in depth.

OnX cadastral line work is from the BLM GCDB (geographic coordinate database) which is a least squares adjusted boundary based off some known survey points. This means that they have precise survey grade coordinates on various section corners throughout a township and then interpolate through mathematics the rest of the township. Depending upon how close the line in question is to a known point or how irregular the township is will effect real world accuracy. It can be almost dead on or a few hundred feet off.
Then, we use this GIS grade line work on our handheld device/ cell phone that only has several meters of accuracy.


OnX mostly utilizes free and public info. If a person wanted to spend the time, they could make a free ArcGIS online account, add in many of the same layers, then get the ArcGIS app on their cell phone.

The function that you would be missing with ArcMAP I believe would be the ability to download a map and go offline.

 

[Rancho Loco]

I use Onx for both work and hunting and haven't seen any issues that weren't outside of what I'd see on Montana Cadastral.

 

[hank4elk]

I use onx here in NM with good results...same as surveyors & the law...
I do know that many fences are not on the property lines & that there is no private land info for Catron county.

 

[RobG]

You’re an engineer right? If you have some, have your surveyors explain this to you more in depth.

OnX cadastral line work is from the BLM GCDB (geographic coordinate database) which is a least squares adjusted boundary based off some known survey points. This means that they have precise survey grade coordinates on various section corners throughout a township and then interpolate through mathematics the rest of the township. Depending upon how close the line in question is to a known point or how irregular the township is will effect real world accuracy. It can be almost dead on or a few hundred feet off.
Then, we use this GIS grade line work on our handheld device/ cell phone that only has several meters of accuracy.


OnX mostly utilizes free and public info. If a person wanted to spend the time, they could make a free ArcGIS online account, add in many of the same layers, then get the ArcGIS app on their cell phone.

The function that you would be missing with ArcMAP I believe would be the ability to download a map and go offline.

Thanks for explaining that. I'm electrical so I don't work with surveyors, but what you are saying explains a lot. It sounds like OnX could do a much better job by downloading the data points for more section corners instead of extrapolating them. I know you can find the lat/long of corners online (http://www.legallandconverter.com/). In other words... OnX should do better.

Where I saw very large errors was in the horizontal section boundaries around Big Timber Creek in the Crazies. The Forest Service maps, available though the Avensa App, had the correct location for the section boundaries, but they don't have all the layers and coverage that OnX does.

 

[Rzrbck918]

What can be equally likely is the private/public fence is in the wrong spot. I personally know of ranchers who've moved fence to give themselves extra acres on their ranch. I also have a friend who owns a ranch that when originally surveyed was done incorrectly to the point where their ranch is 80 acres larger than the 640 they bought. It's been in their family for generations at this point though and the forest service either doesn't know or doesn't care.

You’re right. That is completely possible.

 

[RobG]

What can be equally likely is the private/public fence is in the wrong spot. I personally know of ranchers who've moved fence to give themselves extra acres on their ranch. I also have a friend who owns a ranch that when originally surveyed was done incorrectly to the point where their ranch is 80 acres larger than the 640 they bought. It's been in their family for generations at this point though and the forest service either doesn't know or doesn't care.

After seeing how far off it can be I would never advise crossing a fence because OnX says the fence is in the wrong place. I might take the gps coordinates and verify the property line and THEN cross it, but not just base don OnX.

 

[Lonesome_God_outdoors]

I agree Rob. I wasn't advocating any action just throwing in another possibility