1. 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)

2. Global Grid – Latitude-Longitude

3. Map Projections
Mercator
Conical
Transverse Mercator
Polyconic

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

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

6. Potential Misfit of Surveyed Sections

7. Grids on Topographic Maps
Township
Boundary
Latitude
Longitude

8. Other Information on Topographic Maps

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

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

11. Reading Topography

12. Creating a Topographic Profile
200
180
160
140
120
140
160

13. Intersection of Topography and Geology

14. 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