Topographic Base MapsTopographic Base Maps Objective – Displays surface features (topography, Objective – Displays surface features (topography,

roads, lakes & river, cultural features) and a grid roads, lakes & river, cultural features) and a grid system (TRS, UTM, Lat/Lon) that allow one to system (TRS, UTM, Lat/Lon) that allow one to readily locate the geologic features portrayedreadily locate the geologic features portrayed

Best choice of base map is largely dependent on Best choice of base map is largely dependent on the map scale the map scale

1:24,000 scale (7.5’ USGS quadrangle)1:100,000 scale (30’x60’ USGS sheet)

GEOL 3000GEOL 3000

Global Grid – Latitude-LongitudeGlobal Grid – Latitude-Longitude

Map ProjectionsMap Projections

Mercator

Transverse Mercator

Conical

Polyconic

Universal Transverse Mercator Universal Transverse Mercator (UTM) Grid(UTM) Grid

Two Versions of North American Datum (NAD) grid – 1927 and 1983

Surveyed Grid Surveyed Grid Township, Range, SectionTownship, Range, Section

Section ~1 sq. mile

Township ~36 sq. miles

Potential Misfit of Surveyed Potential Misfit of Surveyed SectionsSections

Grids on Topographic MapsGrids on Topographic Maps

Latitude Longitude

TownshipBoundary

Other Information on Topographic Other Information on Topographic MapsMaps

Elements of the Elements of the Topographic Topographic

MapMap

USGS Topographic Map Symbol Website

<click here>

Topographic Contour LinesTopographic Contour Linesconnects points of equal elevationconnects points of equal elevation

Rules:Rules:

• Lines never cross

•Lines never end

•Lines “V” upstream

•Lines encircle hills and depressions

Reading TopographyReading Topography

Creating a Creating a Topographic Topographic

ProfileProfile

Intersection of Topography and Geology Intersection of Topography and Geology

Standard Topographic Basemap ScalesStandard Topographic Basemap Scales

1° x 2 ° Sheets1:250,000

1” = 4 miles

7.5’ Quadrangles1:24,000

1” = 2000 feet

See DNR Maps Website for MN topo maps<click here>

Also: 30’x60’ sheets, 1:100,000, 1”=1.5 miles