B4J Question calculat area

[PoleStar]

hi
I converted LatLon To XY and calculated the area of polygons with this (www.mathopenref.com/coordpolygonarea2.html) algorithm in google map
now how can convert area unit to Meter 2
Great thanks

 

[PoleStar]

i want make like this
https://www.freemaptools.com/area-calculator.htm

 

[PoleStar]

No one help me ?

 

[jmon]

There are no built in functions for that. You'll have to compute it by doing some maths. There are lots of examples on internet for that : https://www.google.co.th/search?q=math compute perimeter polygon&oq=math compute perimeter polygon

Edit: more example http://www.mathopenref.com/coordpolygonarea.html
http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates

 

[Mark Read]

There is an excel spreadsheet - here, which should help you.

 

[klaus]

I converted LatLon To XY and calculated the area of polygons...

How have you done this?
I suppose that LatLon coordinates are degrees, how did you convet them to XY.
Without knowing what you have done impossible to give a concrete advice.

 

[PoleStar]

There are no built in functions for that. You'll have to compute it by doing some maths. There are lots of examples on internet for that : https://www.google.co.th/search?q=math compute perimeter polygon&oq=math compute perimeter polygon

Edit: more example http://www.mathopenref.com/coordpolygonarea.html
http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates

I 'm calculation but I do not know unit
I would like meter unit

There is an excel spreadsheet - here, which should help you.

tanks but this is not area calculation

How have you done this?
I suppose that LatLon coordinates are degrees, how did you convet them to XY.
Without knowing what you have done impossible to give a concrete advice.

https://www.b4x.com/android/forum/threads/find-screen-x-y-of-google-map.61309/#post-386710

 

[Mark Read]

tanks but this is not area calculation

Not quite sure what you looked at but look at the tab "area & perimeter" again! The input is lat and lon.

 

[PoleStar]

Not quite sure what you looked at but look at the tab "area & perimeter" again! The input is lat and lon.

Compared with : https://www.freemaptools.com/area-calculator.htm
Results not equal

 

[klaus]

Try this:

Dim ll as LatLng
ll.Initialize(0, 1)
Dim xy() as Double =LatLonToXY(ll)

The coordinate is 1 degree on the equator.
What values do you get?
If you get something similar to 111.319 the unit is km.
If you get something similar 111319 the unit is m.
If you get something similar 69.171 the unit is mile.

My GoogleMap doesn't work anymore so I couldn't test it.