App for field measurements

[Neddy flanders]

Any suggestions on an Android app for measuring small stewardship or undrilled areas. Most I tried yesterday were so inaccurate they were worthless.

 

[farmerm]

Any suggestions on an Android app for measuring small stewardship or undrilled areas. Most I tried yesterday were so inaccurate they were worthless.

The issue with inaccuracy isn't the apps, it is primarily the limitations of the none corrected GPS chip in your Android device! At best, with no trees around the accuracy will be +/-5m at any given point, Also remember unless your are on a bowling green flat field the measurements from GPS will be lower than measurements you take on the ground. Point A to point B might be 10m when plotted in 2 dimensions but if point B is lower than point A the length of the slope A to B is longer than the distance between point A and B. I have some sloping 6m margins that appear to be only 4m if you measure them on satellite images.

 

[Zippy768]

Fields Area Measure I use for part spraying or ferting areas. Not sure in the +/- accuracy

 

[Brisel]

CHS Area Finder app. Good enough for mapping odds & sods but I'd want something better for RPA purposes. As above, your smartphone has no correction signal even with good 3/4G.

How about a measuring wheel for some of the sides then Google Earth Pro for the rest? Magic isn't bad either these days.

 

[Savage]

Measure Map. I’m using on iPhone, but it’s also available for Android

Measure Map

measuremapapp.com

 

[Bruce_D]

If you're after a higher level of accuracy then it could be worth getting a drone operator to do a one off survey flight of all your fields to then calculate area. They should be able to create a 3D map for an improved accuracy.

If its just simple area cals, and not too worried about exact calculations, then I think you can use either Google Earth as suggest above, or planet.com can give you area cals, using a free 14 day trial.

 

[Northern farmer]

Can you explain more how a drone survey works? My assumption is that even a high accuracy (RTK) GNSS receiver at the drone is not sufficient for high accuracy mapping because of the camera angle uncertainty (tilt). Not sure about geometry errors from the camera lens. Even SLR lenses have some errors.

I assume these photos need to be calibrated against known reference points. If this is the case, wouldn't it be simpler to just walk/drive around the field with a cheap but high accuracy GNSS receiver (on RTK) if the field area is of interest (perhaps border mapping too)?

Perhaps simply less work for complex fields with a set of drone photos and a few calibration points?

 

[Bruce_D]

Because the drone will take several photos with high over lap, which it then uses to create a point cloud for the 3D model, it is possible to achieve fairly accurate results without RTK, just with one or two reference points. If you’ve got a handheld GNSS receiver then yes you can achieve the same result.

It depends how big an area you’re doing and how accurate you want. Drones can get a 99% accuracy in the fraction of the time, specially for large areas.

 

[Bruce_D]

Fixed wing drones can map around 300 acres in an hour, rotated can do about 100 acres in an hour; I’d be impressed if you can walk that fast around your fields. Lol.

 

[steveR]

Any suggestions on an Android app for measuring small stewardship or undrilled areas. Most I tried yesterday were so inaccurate they were worthless.

As others have said and you have found out, the average phone GPS is not that wonderful when it comes to accuracy.

It's a bit of pain to link up initially, but using a Garmin Glo connected to your phone or tablet will improve accuracy a lot, down to 50cm in good locations. Happily, we are quite flat!!

I use Field Navigator for working and for measurement. Quite liked the Farmis Field Area Measurement app...

 

[Northern farmer]

Because the drone will take several photos with high over lap, which it then uses to create a point cloud for the 3D model, it is possible to achieve fairly accurate results without RTK, just with one or two reference points. If you’ve got a handheld GNSS receiver then yes you can achieve the same result.

It depends how big an area you’re doing and how accurate you want. Drones can get a 99% accuracy in the fraction of the time, specially for large areas.

I thought drones might not rely on their GPS but rather stitch overlapping high resolution photos as you say. I'm still slowly catching the complete picture. These photos do not have any accurate dimensions, one would need a very accurate altitude info for that. I'm still assuming some sort of a reference for scaling. Is that from Google Earth, probably not because you could do the whole thing then from google aerial photos. A couple of RTK surveyed reference points would work without too much additional work.

I understand walking around a big field takes time but in the context of the OP I doubt commercial drone mapping would be attractive. I can agree drone mapping being a good solution for many other scenarios.

 

[clbarclay]

Are they expecting areas to be measured to a ten thousandth of a hectare? Unless it is only small patches, chances are no method will be absolutely accurate anyway.

You can setup RTK receivers to work with mobile phones and tablets though in stead of using the devices inbuilt GPS.

 

[jack6480]

Planimeter

 

[steveR]

The issue with inaccuracy isn't the apps, it is primarily the limitations of the none corrected GPS chip in your Android device! At best, with no trees around the accuracy will be +/-5m at any given point, Also remember unless your are on a bowling green flat field the measurements from GPS will be lower than measurements you take on the ground. Point A to point B might be 10m when plotted in 2 dimensions but if point B is lower than point A the length of the slope A to B is longer than the distance between point A and B. I have some sloping 6m margins that appear to be only 4m if you measure them on satellite images.

What sort of slope gradient are the margins on that are you seeing that difference between actual and sat measurements?

 

[v12cat]

What sort of slope gradient are the margins on that are you seeing that difference between actual and sat measurements?

.....well it would require a slope of over 45 degrees on an image taken from directly above.

 

[arwooldridge]

As Clbarclay said, you can set an external gps RTK receiver, set phone to use use as mock GPS. I use bluetooth link to both send the NTRIP corrections to the RTK receiver and receive the accurate mock GPS location back.