Area Calculation Using Previously Saved Waypoints?

[kiwitonita]

Is it possible to calculate area on the GPS by using previously saved waypoints on the late model 76 and 60 series Garmin units? I would like to measure the size of fields by making each fence corner a waypoint. There will be over 200 waypoints collected. I'd then want to select the waypoints that make up a field and get the GPS to calculate the area. It should be simple but I cannot see how to do it. I know there are programs such as GPS Utility that will do it but that's back on the computer and it'd be useful to be able to do it in the GPS. MapSource will not calculate the area of a route (only a closed track).

 

The track method of area calculation is not suitable as it relies on the fence lines being tracked carefully which is not practical. While I'm about it - the manuals for the Garmin GPSMAP 60CS & 76CS for example do not explain the Area Calculation page - it's like a hidden feature buried in the Page Sequence options and uses the manual track method. I've also asked on the Garmin site so will let you know of any response.

 

I'd also normally search this site but the search function is down. I tried a search using Google and limiting the domain to forums.Groundspeak.com/GC but no joy.

 

Thanks for any tips you can provide.

[Grasscatcher]

The units will only do area calculation internally using the track method.

However......I had to do an area calculation the way you need to do it once and here's how.

Go to the first corner and while standing there, "clear tracklog", then save a waypoint, turn unit off.(leave it off until you get to next point)

Go to second point, turn unit on and let it obtain "lock", save waypoint, turn unit off, etc,etc,etc

Unit will draw straight "tracks" between "off" and "on " points without actually having to follow the fence line since that is impossible.

When you get to the last corner, after having saved your last waypoint, save the track and it will show the enclosed area.

The waypoints will actually have nothing to do with it except the will be located where the "track" bends or makes a corner.

I believe that is the only way to do it internally within the unit.

 

In other software, USAPhotomaps and Expert GPS, you can do it. Dan Foster from Topografix (see some of his posts on this forum) can explain the particulars better than I.

 

Good Luck

Edited January 25, 2006 by Grasscatcher

[topografix]

Calculating area in ExpertGPS

[+Timpat]

Is it possible to calculate area on the GPS by using previously saved waypoints on the late model 76 and 60 series Garmin units?

Here's one solution that I have used. In MapSource, pick the fence corner waypoints you want to use for your area calculation and use the Route Tool to create a route for each "field". Create as many routes for as many fields you want. Save this new MapSource file as a .gpx file.

 

Then download this GPS Utility freeware program. It's great for many uses I've found. Open your newly created .gpx file. It will open a screen displaying the waypoints. Go to the tab VIEW/Routes, then VIEW/Reports. Select the the Route Information option in the box at the upper left, then with the up/down arrows select the route for the field of interest. Each route you created will use the waypoint names that describe the limits of your field.

 

Here's an example of the resulting Route Information:

 

Route number 1

Route name 001 to 001

Number of waypoints 5

Route Distance(ft) 19320

 

ID Coordinate Degs Dist(ft)

001 N44°33.9023' W073°54.075 088 6248

002 N44°33.9413' W073°52.633 175 3653

003 N44°33.3428' W073°52.560 268 5773

004 N44°33.3168' W073°53.892 347 3647

001 N44°33.9023' W073°54.075

 

End to Start(ft) 0

Area enclosed(acres) 498.884

 

Now you have each leg distance, total distance (perimeter), and area in acres. Divide acres by 43,560 (SF in an acre) to get a total area in Square Feet.

 

Good luck, and report back with how it works for you?

[kiwitonita]

Thanks for the assistance - as always the knowledge is quickly shared. I also asked on the local NZ site NZ GPS Society which revealed the intersting point that it's easy to do the "area by waypoint selection" function with a Garmin Legend but not possible (as easily) in the newer model 60 & 76 series.

 

Good to see that MapSource is improving it's functionality in this area too. Previously I'd used GPS Utility to calculate the areas from waypoints.

Edited January 28, 2006 by kiwitonita

[+Timpat]

I just discovered that an area calculation can be done using your Waypoints directly in MapSource. At least using Mapsource v.6.10.0.2 beta. With MS open and having your waypoints on screen, go to Tools/Track Draw, and start drawing a polyline from your first point, thru all points you want included, then end it at your starting point.

 

You will now have "Track 001" created. Right Click on the track and then on Track Properties. It gives you the the lenghts of each leg, the leg course, the coordinate of each point you used, a total lenght, and last bu tnot least, the AREA, in square feet.