If I wanted to project latitude & longitude data for the contiguous United States (the United States excluding Alaska and Hawaii), which projection would I use? I prefer more accurate distances followed by shapes
The Albers equal area conic is the typical projection for historical USGS maps of the lower 48, it being a general-purpose low-distortion compromise for mid-latitude short and wide extents.
As a reference on map projections, I like the ESRI book Understanding Map Projections. Its first 30 pages are not unlike a short textbook, followed by ~70 pages of appendix on individual projections, their uses, strengths, weaknesses, etc.
- Albers, pg 37
- Lambert, pg 66
- equidistant conic, pg 53
ESRI has defined three projections especially for the contiguos United states. These are included in QGIS as well:
+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=37.5 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs
+proj=lcc +lat_1=33 +lat_2=45 +lat_0=39 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs
+proj=eqdc +lat_0=39 +lon_0=-96 +lat_1=33 +lat_2=45 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs
So it is up to you which projection characteristics you need: equal area, equal distance or conformal.
Visit this page to see the differences: http://www.radicalcartography.net/?projectionref
PROJ has a Modified Stereographic of 48 U.S. (
It is based on a modified-stereographic conformal projection detailed by Snyder (1987) (p.203–212). Here is the estimate of scale factors from the document:
The down-side of this projection is that it is seldom used and has limited support. For instance, to use with QGIS, a custom CRS needs to be created with a PROJ string
There are a few "CONUS" projections that are registered with EPSG. Here are some for specific datums:
If shape is important, consider a Lambert conic conformal projection, with two standard latitudes. Distances will be consistent in the vicinity of each of the standard parallels. See
You could also consider some sort of "equidistant" projection. However, distance scale will never be true everywhere; only true from one or two points (in all directions) or from one line (in a single direction).