d3 mercator projection measuring distance (or converting) in meters

Asked Oct 16 '14 at 13:49

Active Oct 16 '14 at 13:49

Viewed 707 times

So I'm currently using this to calculate the area of a polygon using mercator projection in d3

The problem is I need to convert it to meters or kilometers. I'm not really sure what formula to use as I think it changes depending on the zoom level correct? Can anybody point me to the right direction to get this formula correct?

I'm actually thinking of switching to leaflet just to get the area. Thoughts?

Thanks!

edited May 23 '17 at 12:20

Community

asked Oct 16 '14 at 13:49

gdubs

2,724
9
55
102

Use [`d3.geo.area()`](https://github.com/mbostock/d3/wiki/Geo-Paths#area) to compute the area and then convert to meters? – Lars Kotthoff Oct 16 '14 at 14:35
right, but how does one convert from pixel to meters (or km)? – gdubs Oct 16 '14 at 14:42
That function computes the area in steradians. – Lars Kotthoff Oct 16 '14 at 14:44
I can't seem to find a way to convert a steradian to meters/km. Only to square degrees which is new to me. Do you have any links where I can read more about it? – gdubs Oct 16 '14 at 15:58
There's more information on wikipedia: http://en.wikipedia.org/wiki/Square_degree – Lars Kotthoff Oct 16 '14 at 17:35

d3 mercator projection measuring distance (or converting) in meters

0 Answers0