[OpenLayers-Users] meters or degrees ?

[Phil Scadden]

> what's the best unite for creating a map ?
> meters or degrees ?
Just make sure you arent confusing units to display on a map with the 
projection? Choosing your projection is a more considerable question. 
Every flat map involves a projection to an xy plane so you cant have 
"degrees" on the map but you can display the degrees corresponding to 
mouse location on the map.

Projection questions for webmaps on OL begin with "are you using google 
maps?". If you then the projection is Google Mercator. If not, then are 
you using another raster base layer? If so then you must use the 
projection of that layer. If not, then questions about what map is for 
arise. Is preservation of shape more important than perservation of 
area? What portion of globe is to be covered etc. The projection "bible" 
- Snyder's "Map Projections - a working handbook" is very useful.

Both depend on what use the map is for. I generally display degrees. The 
meters values depend on what projection was used and may or may not mean 
anything to the user. A distance tool can be used where meters or nmi 
are definitely more meaningful than degrees.


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