unit for area calculation?

[+neat_guy]

I haven't kept up on the new units for a year or so, anybody know of any with a reliable area calculation? I have a Garmin Oregon which I have found about useless for this purpose, but great for everything else. I do a lot of recording borders of farm fields and such with an HP Ipaq with third party software but really would like a navigation type unit (Nuvi, Roadmate, etc.) with this capability. I think I'm looking for a needle in a haystack, but if anybody would know of anything, I would find them on here! Thanks

[Grasscatcher]

Why do you consider the Oregon "almost useless for this"?

Mine (Oregon 550) has worked fine for several years for that purpose. (water comissioner in Colorado)

Checking area of ponds and or fields.

Prior to that I used a Map76CSx, a Map76CS, a Map 76, and going all the way back to a 12XL.

All very repeatable and accurate. No, not survey quality accuracy, but very reasonable accuracy when compared to surveys.

 

What's not working right?

 

First , "clear current track" at your starting point

I walk a path around a pond close to waterline or a path around a field close to the fenceline to create a "closed track". Save it, and then go to Track Manager, select it, then View on Map, touch the bar across the top of screen....one of the data shown is "area".

 

Sometimes , you can't physically "close" the track in your actual travel. What the unit does in that case is theoretically draw a straight line between your end point and the original start point.(to make a closed shape)

 

.... or for simple shapes, GPS the corners and use third party mapping software.

[+Walts Hunting]

I also used my Oregon several times for area calculation. It wasn't for my job. I did my property and some others for fun. Worked fine.

[+neat_guy]

I've tried different area calculations many times with my Oregon and not once has it come out close. Many times the field shape isn't even close. Most of these I am not under any obstructions from satellite view or any other hinderences. One of the most common frustrations in doing these field "borders" is that if I begin in a given spot, encircle the field, and end at the same spot, the unit says I am anywhere up to 350' from that spot. This is where my opinion almost useless comes in.

[Grasscatcher]

Given your explanation, I would agree......

There's got to be something else going on.

 

Are you sure that the unit has been on long enough to "settle down" and get a good "position lock" at the starting point before you start moving?

 

For track logging are you using "Auto" method and "most often" for logging interval?

 

Save a waypoint at the start point and each corner and endpoint and see if the track downloaded afterwards passes through each. ....and if the SP and EP coordinates are very close to being the same.

Edited February 6, 2012 by Grasscatcher

[+webscouter.]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

[39_Steps]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

Are you sure? Do some Garmin units purposely log track coordinate points as snap to road grid tracks? Or is this just an uncorrected bug?

[seldom_sn]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

Are you sure? Do some Garmin units purposely log track coordinate points as snap to road grid tracks? Or is this just an uncorrected bug?

If the OP is trying to get accurate points and tracks, I'm pretty sure he doesn't want to "Snap To" anything.

[+Walts Hunting]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

Are you sure? Do some Garmin units purposely log track coordinate points as snap to road grid tracks? Or is this just an uncorrected bug?

 

Not a bug but one of the settings. It is most often used in the automotive mode. It can cause a problem when you drive as close as possible to a cache and then start to walk. It will lock on the road and not change. It does serve a purpose since w/o it sometimes the icon will drift off off the road on the map screen. In geocaching profiles it is turned off.

 

If you are using a profile that has the lock on road turned on trying to do a walk around an area you could get HUGE errors. Maybe as high as 350'.

 

I think the Montana has the ability to set it so that it automatically changes out of lock on road to direct mode when getting close to the goal.

 

It would be nice to set that on my android bionic since in some areas where I am now it shows up off the road and tries to turn back to the road I am on at every intersection.

[7rxc]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

Are you sure? Do some Garmin units purposely log track coordinate points as snap to road grid tracks? Or is this just an uncorrected bug?

I always thought that was limited to the map display, not tracks... those would be from the data received by the GPSr.

Now I have to think about that... Still, it would be something to check, it's only a setting. Speaking of which, Isn't there a selection in the menu (of many Garmins) for simply doing Areas, without saving a file? I was looking at an Etrex 10 manual and it seemed to be you just selected that and hit start, walked around to the beginning and hit stop and it did the rest. If a 10 can do it, why not an Oregon... hmm I seem to remember seeing it in my Map 60cx and legend as well. hhmmm! I better look, I sure could use it myself.

 

Doug 7rxc

[Grasscatcher]

Also make sure the lock on road isn't checked. That can cause the unit to try to lock to the nearest road and not be very repeatable.

Are you sure? Do some Garmin units purposely log track coordinate points as snap to road grid tracks? Or is this just an uncorrected bug?

I always thought that was limited to the map display, not tracks... those would be from the data received by the GPSr.

Now I have to think about that... Still, it would be something to check, it's only a setting. Speaking of which, Isn't there a selection in the menu (of many Garmins) for simply doing Areas, without saving a file? I was looking at an Etrex 10 manual and it seemed to be you just selected that and hit start, walked around to the beginning and hit stop and it did the rest. If a 10 can do it, why not an Oregon... hmm I seem to remember seeing it in my Map 60cx and legend as well. hhmmm! I better look, I sure could use it myself.

 

Doug 7rxc

 

7RXC,

Yes, just FYI, the Oregon has that same setting/button, but I was just describing the way I've done it for years (still do) and know to be accurate, in case of the possibility that the unit might do something differently internally with the data(doing it the other way). (Not that it's likely)

 

My described way has worked accurately over several different models.

 

The "snap to" idea might be a possible source of error....hadn't thought of that.......then again I probably wouldn't because I NEVER use that feature. I may have to think about how to experiment with how to tell whether the GPS logs tracks where it "actually is" or "over there" where it snaps to ...with that feature turned on.

 

It's going to calculate the area "inside" the logged track in either case, so that IS a possible source of error. (that I would have never encountered)

Edited February 6, 2012 by Grasscatcher

[xyzee]

Amen on all of the good info above.

Several years ago, I found a "cheat" method, so I didn't have to walk the barbed wire fence line.

I was using a 60CSx, and I always let it sit out in the open for 15 or 20 min before using it for a test etc. After picking it up, it stays at least at eye level, so it dosn't loose Sat lock, until I'm finished.

Tracks setup to Time, one second.

Then over to corner 1, hold the unit over the post and after about 2 sec cut the Tracks on for about 3 sec, then off. Now I can walk over to corner 2 the easy way, and don't have to fight the fence. Several seconds over cor 2, enough to let it settle, but before the SiRF bounce starts to start, then several seconds of tracks for that point. Then do the rest of the corners the same. This way the receiver draws the straight line from cor to cor, and I don't have to walk it. It also draws the last line back to the starting point.

I had to walk the curved line part, on one piece of property, just like around the whole pond.

 

I tried to let the 60 "do" the acerage on this property, by using the Demo Mode. I have a Route of the corners made up, so I hoped that I could reposition my location on to cor 1, activate the tracks, on to Compass Page, hit the Rocker up one time to 10 mph, and watch it make tracks as it navigated the route. I failed. Tried lots of different settings, even pulled the Area Calculation Page out of the Page Sequence, and tried it.

It navigated the route ok, but no tracks for getting the acrs.

 

I did a fun test a few days ago, set the Tracks to Time with all zeros, walked out about 200 ft, then back with the Distance set with all zeros. Got the same results as with the unit set to Auto.

[DManel]

I want to buy a new GPS, tired of my phone...

 

But I want something mainly for area calculation, as it is part of my job, to calculate property areas and so on.

Will also use it for geocaching, but mainly for terrain measurements, like areas.

 

From your experience with your devices, with one is the most reliable to do this specific task? How accurate?

 

I can't find info on that anywhere!!

[39_Steps]

I want to buy a new GPS, tired of my phone...

 

But I want something mainly for area calculation, as it is part of my job, to calculate property areas and so on.

Will also use it for geocaching, but mainly for terrain measurements, like areas.

 

From your experience with your devices, with one is the most reliable to do this specific task? How accurate?

 

I can't find info on that anywhere!!

I see that my Delorme PN-60 has automatically closed the loop of linear track points on my latest 20 mile track log and calculated the Area of the polygon. Other Linear profiling views and statistics are available for display on either the PN-60 or bundled topographic software.

 

A user who wanted best possible accuracy without post processing would need to get a good satellite lock at a point on the polygon before opening a new track file and walking/riding the perimeter. However, if it is necessary to edit the linear track log file to exclude portions of the point log, bundled Topo9 North America could be used on a PC.

Edited June 11, 2012 by 39_Steps

[MtnHermit]

I've tried different area calculations many times with my Oregon and not once has it come out close. Many times the field shape isn't even close. Most of these I am not under any obstructions from satellite view or any other hinderences. One of the most common frustrations in doing these field "borders" is that if I begin in a given spot, encircle the field, and end at the same spot, the unit says I am anywhere up to 350' from that spot. This is where my opinion almost useless comes in.

I'd be curious if your Oregon has up-to-date firmware, both the Garmin software and the GPS chip firmware. All your symptoms could be explained by old firmware.