Maps, Charts, and Photos - Frequently Asked Questions

Topographic Maps

Reading Topographic Maps

Aerial Photos

Geologic Maps

Map Coordinates

Digital Maps


Topographic Maps

Q1. Can I view USGS topographic maps online?     Back

A list of online map viewers is provided on the Links to Related Topics page.


Q2. Where can I buy topo maps?     Back

The Maine Geological Survey sells U.S. Geological Survey topographic maps for Maine at scales of 1:24,000 (707 maps cover the state), 1:100,000 (35 maps cover the state), 1:250,000 (13 maps cover the state), and 1:500,000 (1 map covers the state). To order maps, go to our Maps, Publications, and Online Data site. Other retailers in Maine can be located using the USGS Map Dealer website. Order maps for other states from the USGS store.


Q3. What quadrangles cover my town or area of interest?     Back

You can find out which quads cover your area of interest by using our publications search page:

  • Use the Zoom In feature on the map of Maine to display your region of interest.
  • By holding down your left mouse button, you may draw a rectangle around the area of interest and enlarge the scale of the display.
  • If the quadrangle outlines and names don't show, zoom in to a smaller area.

Q4. Which USGS quadrangle covers the geographic feature I'm interested in?     Back

Use the USGS Geographic Names Information System to search for geographic locations by name. This site also provides direct links to online map viewers, centered on the geographic feature requested.


Q5. Where can I find out-of-print 15-minute topo maps?     Back

  • Historic Maps of New England and NY - University of New Hampshire Dimond Library
  • Historical Maps - this site, hosted by MyTopo, is an expansion of the Historic Maps of New England site hosted at UNH. The site has been expanded to include Delaware, Maryland, New Jersey, New York, Ohio, Pennsylvania, and West Virginia.

Reading Topographic Maps

Q6. Where can I find an explanation of the symbols on USGS topographic maps?     Back

Refer to the U.S. Geological Survey site: Topographic Map Symbols.


Q7. How do I read the scale on a map?     Back

Refer to the U.S. Geological Survey site: Map Scales.


Q8. How do I correct a magnetic compass heading to make it refer to true north? If magnetic north moves a different amount each year, how do I find the correction value in the future?     Back

You add or subtract the declination from the 360 degrees of the compass. Consult the following sites for more information:


Aerial Photos

Q9. Can I view aerial photos for Maine online?     Back

The Maine Office of Geographic Information Services provides an Aerial Photography Viewer. Other online viewers are listed on the Links to Related Topics page.


Q10. Does MGS have any air photos available to look at?     Back

The Maine Geological Survey has two sets of U.S. Department of Agriculture aerial photographs covering Maine, a set at a scale of 1:20,000 from the 1960's and a set at a scale of 1:40,000 from the late 1970's. These photos are available for use at the Maine Geological Survey during office hours.


Q11. Where can I buy aerial photos?     Back

A list of sources of aerial photograph for Maine is contained in Aerial photographs of Maine - Views from the sky (PDF, 0.4Mb).


Geologic Maps

Q12. How can I locate geologic maps in other states?     Back

The U.S. Geological Survey, in cooperation with the Association of American State Geologists, maintains the National Geologic Map Database. This site contains a geoscience map catalog, an image library, a geologic names lexicon, and a listing of new mapping.


Map Coordinates

Q13. I need to locate a satellite TV dish. What's the latitude and longitude of my house?     Back

You can determine your latitude and longitude coordinates online using the Maptech MapServer. Simply enter the name of your town and the state on the entry screen and move to the map of your town. Locate your house, and then move the cross-hairs to that position, the latitude and longitude will appear in the boxes to the left of the map.


Q14. Where can I find information about datums and coordinate systems?     Back

National Geodetic Survey - Frequently Asked Questions - provides information on datums, gps, and coordinate systems.


Digital Maps

Q15. Where can I find digital geologic map data?     Back

A variety of digital data layers are available for download. Statewide digital layers of sand and gravel aquifers, surficial materals, coastal bluff hazards, generalized bedrock geology, and generalized surficial geology are available through the Maine Office of GIS. Digital layers of detailed surficial geology quadrangles are available through the Maine Geological Survey website. Datasets may be downloaded free of charge over the internet.


Q16. Where can I find digital topographic data?     Back

Digital topographic data is available from the Maine Office of Geographic Information Systems and the U.S. Geological Survey.


Last updated on April 9, 2012