Which projection is best for mapping the contiguous United States?

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

• different projections have different characteristics. What is more important: shapes, distances, or cardinal directions? – mr.adam Apr 6 '15 at 16:21
• @mr.adam - Distance followed by shape – DenaliHardtail Apr 6 '15 at 17:21
• us48 otherwise known as alber usgs, USA_Contiguous_Albers_Equal_Area_Conic_USGS_version, EPSG:5070 – Brad Nesom Apr 6 '15 at 18:44
• – Chris W Apr 6 '15 at 21:59

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
• Good direction indeed! all the geographic coverage is illustrated visually. – SIslam Aug 25 '16 at 12:58
• the one-sixth rule discussed in ESRIs book for albers equal area conic suggests standard parallels for the US of about 22 (26 - (49 - 26)*(1/6)) and 53 (49 + (49 - 26)*(1/6)). but I've found calculations over small areas appear to improve more from picking parameters close to the site than from picking a better projection (e.g. the more simple azimuth equidistant projection appears to work well for a single US state if the tangency point is chosen at the state centroid, better than an albers projection with these US-wide parameters) – Richard DiSalvo Apr 29 at 6:20

ESRI has defined three projections especially for the contiguos United states. These are included in QGIS as well:

EPSG:102003 USA_Contiguous_Albers_Equal_Area_Conic
+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

EPSG:102004 USA_Contiguous_Lambert_Conformal_Conic
+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

EPSG:102005 USA_Contiguous_Equidistant_Conic
+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.