Topographic Base Maps Objective – Displays surface features (topography, roads, lakes & river, cultural features) and a grid system (TRS, UTM, Lat/Lon) that allow one to readily locate the geologic features portrayed Best choice of base map is largely dependent on the map scale 1:24,000 scale (7.5’ USGS quadrangle) 1:100,000 scale (30’x60’ USGS sheet)

Global Grid – Latitude-Longitude

Map Projections Mercator Conical Transverse Mercator Polyconic

Universal Transverse Mercator (UTM) Grid Two Versions of North American Datum (NAD) grid – 1927 and 1983

Surveyed Grid Township, Range, Section Township ~36 sq. miles Section ~1 sq. mile

Potential Misfit of Surveyed Sections

Grids on Topographic Maps Township Boundary Latitude Longitude

Other Information on Topographic Maps

Elements of the Topographic Map USGS Topographic Map Symbol Website <click here>

Topographic Contour Lines connects points of equal elevation Rules: Lines never cross Lines never end Lines “V” upstream Lines encircle hills and depressions

Reading Topography

Creating a Topographic Profile 200 180 160 140 120 140 160

Intersection of Topography and Geology

Standard Topographic Basemap Scales 7.5’ Quadrangles 1:24,000 1” = 2000 feet See DNR Maps Website for MN topo maps <click here> 1° x 2 ° Sheets 1:250,000 1” = 4 miles Also: 30’x60’ sheets, 1:100,000, 1”=1.5 miles